Start to fix null safety migration errors

lib/ui/screens/authorized_group_page_screen.dart

@@ -27,14 +27,14 @@ Color get _headerColor => Colors.blueAccent.shade700;
 
 class AuthorizedGroupPageScreen extends StatefulWidget {
   final AdvancedGroupInfo advancedGroupInfo;
-  final int conversationID;
+  final int? conversationID;
   final Function() needRefresh;
 
   const AuthorizedGroupPageScreen({
-    Key key,
-    @required this.advancedGroupInfo,
-    @required this.conversationID,
-    @required this.needRefresh,
+    Key? key,
+    required this.advancedGroupInfo,
+    required this.conversationID,
+    required this.needRefresh,
   })  : assert(advancedGroupInfo != null),
         assert(needRefresh != null),
         super(key: key);
@@ -49,42 +49,42 @@ class _AuthorizedGroupPageScreenState
     with SingleTickerProviderStateMixin {
   AdvancedGroupInfo get _group => widget.advancedGroupInfo;
 
-  TabController _tabController;
+  TabController? _tabController;
 
   List<_GroupPageTab> get _tabs => [
         // Posts list
         _GroupPageTab(
           widget: (c) => GroupPostsSection(group: _group),
-          label: tr("Posts"),
+          label: tr("Posts")!,
         ),
 
         // Forez presence tab
         _GroupPageTab(
           widget: (c) => ForezPresenceSection(groupID: _group.id),
-          label: tr("Presence"),
+          label: tr("Presence")!,
           visible: _group.isForezGroup,
         ),
 
         // About the group
         _GroupPageTab(
           widget: (c) => AboutGroupSection(group: _group),
-          label: tr("About"),
+          label: tr("About")!,
         ),
 
         _GroupPageTab(
           widget: (c) => GroupMembersSection(groupID: _group.id),
-          label: tr("Members"),
-          visible: _group.isAtLeastModerator || _group.isMembersListPublic,
+          label: tr("Members")!,
+          visible: _group.isAtLeastModerator || _group.isMembersListPublic!,
         )
       ].where((element) => element.visible).toList()
 
         // Add group conversations
         ..insertAll(
             (_group.isForezGroup ? 2 : 1),
-            _group.conversations
+            _group.conversations!
                 .map((e) => _GroupPageTab(
                     widget: (c) => GroupConversationSection(conv: e),
-                    label: e.name))
+                    label: e.name!))
                 .toList());
 
   @override
@@ -94,7 +94,7 @@ class _AuthorizedGroupPageScreenState
       initialIndex: widget.conversationID == null
           ? 0
           : (_group.isForezGroup ? 2 : 1) +
-              _group.conversations
+              _group.conversations!
                   .indexWhere((element) => element.id == widget.conversationID),
       vsync: this,
     );
@@ -104,7 +104,7 @@ class _AuthorizedGroupPageScreenState
 
   @override
   void dispose() {
-    _tabController.dispose();
+    _tabController!.dispose();
     super.dispose();
   }
 
@@ -189,7 +189,7 @@ class _AuthorizedGroupPageScreenState
               _group.isAdmin
                   ? IconButton(
                       icon: Icon(Icons.settings, color: _headerTextColor),
-                      onPressed: () => MainController.of(context).push(
+                      onPressed: () => MainController.of(context)!.push(
                           GroupSettingsScreen(groupID: _group.id),
                           canShowAsDialog: true))
                   : Container(),
@@ -207,9 +207,9 @@ class _GroupPageTab {
   final String label;
 
   const _GroupPageTab({
-    @required this.widget,
+    required this.widget,
     this.visible = true,
-    @required this.label,
+    required this.label,
   })  : assert(widget != null),
         assert(visible != null),
         assert(label != null);

lib/ui/screens/call_screen.dart

@@ -33,16 +33,16 @@ class CallScreen extends StatefulWidget {
 
   /// Use custom application bar. This function takes as parameter a nullable
   /// String which is the title of the conversation
-  final PreferredSizeWidget Function(String) buildCustomAppBar;
+  final PreferredSizeWidget Function(String?)? buildCustomAppBar;
 
   /// Execute custom action when the call is closed
   ///
   /// The default behavior is to pop the page
-  final void Function() onClose;
+  final void Function()? onClose;
 
   const CallScreen({
-    Key key,
-    @required this.convID,
+    Key? key,
+    required this.convID,
     this.floatingButtons = true,
     this.buildCustomAppBar,
     this.onClose,
@@ -60,15 +60,15 @@ class _CallScreenState extends SafeState<CallScreen> {
   int get convID => widget.convID;
 
   // State properties
-  Conversation _conversation;
-  String _convName;
-  CallConfig _conf;
+  late Conversation _conversation;
+  String? _convName;
+  late CallConfig _conf;
   var _error = false;
-  CallMembersList _membersList;
-  UsersList _usersList;
-  final _peersConnections = Map<int, RTCPeerConnection>();
-  final _renderers = Map<int, RTCVideoRenderer>();
-  MediaStream _localStream;
+  CallMembersList? _membersList;
+  late UsersList _usersList;
+  final _peersConnections = Map<int?, RTCPeerConnection>();
+  final _renderers = Map<int?, RTCVideoRenderer>();
+  MediaStream? _localStream;
   var _isLocalStreamVisible = true;
   var _hideMenuBars = false;
 
@@ -81,16 +81,16 @@ class _CallScreenState extends SafeState<CallScreen> {
       _conversation.callCapabilities == CallCapabilities.VIDEO;
 
   bool get isStreamingAudio =>
-      _localStream != null && _localStream.getAudioTracks().length > 0;
+      _localStream != null && _localStream!.getAudioTracks().length > 0;
 
   bool get isStreamingVideo =>
-      _localStream != null && _localStream.getVideoTracks().length > 0;
+      _localStream != null && _localStream!.getVideoTracks().length > 0;
 
   bool get isAudioMuted =>
-      isStreamingAudio && !_localStream.getAudioTracks()[0].enabled;
+      isStreamingAudio && !_localStream!.getAudioTracks()[0].enabled;
 
   bool get isVideoMuted =>
-      isStreamingVideo && !_localStream.getVideoTracks()[0].enabled;
+      isStreamingVideo && !_localStream!.getVideoTracks()[0].enabled;
 
   @override
   void initState() {
@@ -137,7 +137,7 @@ class _CallScreenState extends SafeState<CallScreen> {
         try {
           if (!_usersList.hasUser(e.userID))
             _usersList.add(await UsersHelper().getSingleWithThrow(e.userID));
-          setState(() => _membersList.add(CallMember(userID: e.userID)));
+          setState(() => _membersList!.add(CallMember(userID: e.userID!)));
         } catch (e, stack) {
           print("$e\n$stack");
         }
@@ -164,7 +164,7 @@ class _CallScreenState extends SafeState<CallScreen> {
       });
 
       // Connect to ready peers
-      for (final peer in _membersList.readyPeers)
+      for (final peer in _membersList!.readyPeers)
         await this._memberReady(peer.userID);
 
       setState(() {});
@@ -183,7 +183,7 @@ class _CallScreenState extends SafeState<CallScreen> {
       await setWakeLock(false);
 
       // Close all ready members
-      for (final member in _membersList.readyPeers)
+      for (final member in _membersList!.readyPeers)
         await _removeMember(member.userID);
 
       // Close local stream
@@ -204,9 +204,9 @@ class _CallScreenState extends SafeState<CallScreen> {
             message: tr("Do you really want to leave this call ?"))) return;
 
     if (widget.onClose == null)
-      MainController.of(context).popPage();
+      MainController.of(context)!.popPage();
     else
-      widget.onClose();
+      widget.onClose!();
   }
 
   /// Start streaming on our end
@@ -232,8 +232,8 @@ class _CallScreenState extends SafeState<CallScreen> {
 
       // Start renderer
       _renderers[userID()] = RTCVideoRenderer();
-      await _renderers[userID()].initialize();
-      _renderers[userID()].srcObject = _localStream;
+      await _renderers[userID()]!.initialize();
+      _renderers[userID()]!.srcObject = _localStream;
       setState(() {});
 
       // Open stream
@@ -244,8 +244,8 @@ class _CallScreenState extends SafeState<CallScreen> {
 
       _peersConnections[userID()] = peerConnection;
 
-      for (final track in _localStream.getTracks()) {
-        await peerConnection.addTrack(track, _localStream);
+      for (final track in _localStream!.getTracks()) {
+        await peerConnection.addTrack(track, _localStream!);
       }
 
       peerConnection.onAddStream =
@@ -275,7 +275,7 @@ class _CallScreenState extends SafeState<CallScreen> {
       await CallsHelper.sendSessionDescription(convID, userID(), offer);
     } catch (e, stack) {
       print("Could not start streaming! $e\n$stack");
-      showSimpleSnack(context, tr("Could not start streaming!"));
+      showSimpleSnack(context, tr("Could not start streaming!")!);
     }
   }
 
@@ -283,7 +283,7 @@ class _CallScreenState extends SafeState<CallScreen> {
   Future<void> _stopStreaming() async {
     // Close peer connection
     if (_peersConnections.containsKey(userID())) {
-      _peersConnections[userID()].close();
+      _peersConnections[userID()]!.close();
       _peersConnections.remove(userID());
 
       await CallsHelper.notifyStoppedStreaming(convID);
@@ -291,13 +291,13 @@ class _CallScreenState extends SafeState<CallScreen> {
 
     // Stop local stream
     if (_localStream != null) {
-      await _localStream.dispose();
+      await _localStream!.dispose();
       _localStream = null;
     }
 
     // Close renderer
     if (_renderers.containsKey(userID())) {
-      await _renderers[userID()].dispose();
+      await _renderers[userID()]!.dispose();
       _renderers.remove(userID());
     }
   }
@@ -324,20 +324,20 @@ class _CallScreenState extends SafeState<CallScreen> {
     // Toggle appropriate mute
     else {
       if (!isVideo)
-        _localStream.getAudioTracks()[0].enabled =
-            !_localStream.getAudioTracks()[0].enabled;
+        _localStream!.getAudioTracks()[0].enabled =
+            !_localStream!.getAudioTracks()[0].enabled;
       else
-        _localStream.getVideoTracks()[0].enabled =
-            !_localStream.getVideoTracks()[0].enabled;
+        _localStream!.getVideoTracks()[0].enabled =
+            !_localStream!.getVideoTracks()[0].enabled;
     }
 
     setState(() {});
   }
 
   /// Call this when a user started to stream media
-  Future<void> _memberReady(int memberID) async {
+  Future<void> _memberReady(int? memberID) async {
     try {
-      _membersList.getUser(memberID).status = MemberStatus.READY;
+      _membersList!.getUser(memberID).status = MemberStatus.READY;
       setState(() {});
 
       // Create peer connection
@@ -353,15 +353,15 @@ class _CallScreenState extends SafeState<CallScreen> {
 
       // Create a renderer
       _renderers[memberID] = RTCVideoRenderer();
-      await _renderers[memberID].initialize();
+      await _renderers[memberID]!.initialize();
 
       // Register callbacks
       peerConnection.onIceCandidate =
           (c) => CallsHelper.sendIceCandidate(convID, memberID, c);
       peerConnection.onAddStream = (s) {
         setState(() {
-          _membersList.getUser(memberID).stream = s;
-          _renderers[memberID].srcObject = s;
+          _membersList!.getUser(memberID).stream = s;
+          _renderers[memberID]!.srcObject = s;
         });
       };
 
@@ -371,7 +371,7 @@ class _CallScreenState extends SafeState<CallScreen> {
       setState(() {});
     } catch (e, stack) {
       print("Could not connect to remote peer $e\n$stack!");
-      showSimpleSnack(context, tr("Could not connect to a remote peer!"));
+      showSimpleSnack(context, tr("Could not connect to a remote peer!")!);
     }
   }
 
@@ -388,13 +388,13 @@ class _CallScreenState extends SafeState<CallScreen> {
       // Check the kind of signal
       // SessionDescription
       if (ev.sessionDescription != null) {
-        await _peersConnections[ev.peerID]
-            .setRemoteDescription(ev.sessionDescription);
+        await _peersConnections[ev.peerID]!
+            .setRemoteDescription(ev.sessionDescription!);
 
         // Send answer if required
-        if (ev.sessionDescription.type == "offer") {
-          final answer = await _peersConnections[ev.peerID].createAnswer({});
-          await _peersConnections[ev.peerID].setLocalDescription(answer);
+        if (ev.sessionDescription!.type == "offer") {
+          final answer = await _peersConnections[ev.peerID]!.createAnswer({});
+          await _peersConnections[ev.peerID]!.setLocalDescription(answer);
 
           await CallsHelper.sendSessionDescription(convID, ev.peerID, answer);
         }
@@ -402,41 +402,41 @@ class _CallScreenState extends SafeState<CallScreen> {
 
       // Ice Candidate
       else {
-        await _peersConnections[ev.peerID].addCandidate(ev.candidate);
+        await _peersConnections[ev.peerID]!.addCandidate(ev.candidate!);
       }
     } catch (e, stack) {
       print("Error while handling new signal ! $e\n$stack");
-      showSimpleSnack(context, tr("Error while processing new signal!"));
+      showSimpleSnack(context, tr("Error while processing new signal!")!);
     }
   }
 
   /// Call this when a user has interrupted streaming
-  Future<void> _removeRemotePeerConnection(int memberID) async {
-    final member = _membersList.getUser(memberID);
+  Future<void> _removeRemotePeerConnection(int? memberID) async {
+    final member = _membersList!.getUser(memberID);
     member.status = MemberStatus.JOINED;
     setState(() {});
 
     if (_peersConnections.containsKey(memberID)) {
-      await _peersConnections[memberID].close();
+      await _peersConnections[memberID]!.close();
       _peersConnections.remove(memberID);
     }
 
     if (_renderers.containsKey(memberID)) {
-      await _renderers[memberID].dispose();
+      await _renderers[memberID]!.dispose();
       _renderers.remove(memberID);
     }
 
     if (member.stream != null) {
-      member.stream.dispose();
+      member.stream!.dispose();
       member.stream = null;
     }
   }
 
   /// Call this when a member has completely left the call
-  Future<void> _removeMember(int memberID) async {
+  Future<void> _removeMember(int? memberID) async {
     await _removeRemotePeerConnection(memberID);
 
-    _membersList.removeUser(memberID);
+    _membersList!.removeUser(memberID);
 
     setState(() {});
   }
@@ -453,7 +453,7 @@ class _CallScreenState extends SafeState<CallScreen> {
     switch (option) {
       // Switch camera
       case _PopupMenuOption.SWITCH_CAMERA:
-        await Helper.switchCamera(_localStream.getVideoTracks()[0]);
+        await Helper.switchCamera(_localStream!.getVideoTracks()[0]);
         break;
 
       // Stop streaming
@@ -478,14 +478,14 @@ class _CallScreenState extends SafeState<CallScreen> {
   /// Build application bar
   PreferredSizeWidget _buildAppBar() {
     if (widget.buildCustomAppBar != null)
-      return widget.buildCustomAppBar(_convName);
+      return widget.buildCustomAppBar!(_convName);
 
     return AppBar(
       leading: IconButton(
         icon: Icon(Icons.arrow_back),
         onPressed: () => _leaveCall(),
       ),
-      title: _convName == null ? CircularProgressIndicator() : Text(_convName),
+      title: _convName == null ? CircularProgressIndicator() : Text(_convName!),
     );
   }
 
@@ -496,7 +496,7 @@ class _CallScreenState extends SafeState<CallScreen> {
       return buildErrorCard(tr("Could not initialize call!"), actions: [
         MaterialButton(
           onPressed: () => _initCall(),
-          child: Text(tr("Try again").toUpperCase()),
+          child: Text(tr("Try again")!.toUpperCase()),
         )
       ]);
 
@@ -526,7 +526,7 @@ class _CallScreenState extends SafeState<CallScreen> {
         padding: const EdgeInsets.all(8.0),
         child: RichText(
             text: TextSpan(
-                children: _membersList
+                children: _membersList!
                     .map((f) => TextSpan(
                         text: _usersList.getUser(f.userID).displayName + " ",
                         style: TextStyle(
@@ -540,7 +540,7 @@ class _CallScreenState extends SafeState<CallScreen> {
 
   /// Videos area
   Widget _buildVideosArea(BuildContext context, BoxConstraints constraints) {
-    final availableVideos = _membersList.readyPeers
+    final List<CallMember> availableVideos = _membersList!.readyPeers
         .where((f) => f.hasVideoStream && _renderers.containsKey(f.userID))
         .toList();
 
@@ -591,12 +591,12 @@ class _CallScreenState extends SafeState<CallScreen> {
   }
 
   Widget _buildMemberVideo(int peerID) {
-    return RTCVideoView(_renderers[peerID]);
+    return RTCVideoView(_renderers[peerID]!);
   }
 
   Widget _buildLocalVideo() {
     return Positioned(
-      child: RTCVideoView(_renderers[userID()]),
+      child: RTCVideoView(_renderers[userID()]!),
       height: 50,
       width: 50,
       right: 10,
@@ -657,12 +657,12 @@ class _CallScreenState extends SafeState<CallScreen> {
               // Switch camera
               PopupMenuItem(
                   enabled: isStreamingVideo,
-                  child: Text(tr("Switch camera")),
+                  child: Text(tr("Switch camera")!),
                   value: _PopupMenuOption.SWITCH_CAMERA),
 
               // Interrupt streaming
               PopupMenuItem(
-                  child: Text(tr("Stop streaming")),
+                  child: Text(tr("Stop streaming")!),
                   value: _PopupMenuOption.STOP_STREAMING)
             ],
             child: _FooterButton(
@@ -679,7 +679,7 @@ class _CallScreenState extends SafeState<CallScreen> {
 }
 
 class _FooterButton extends StatelessWidget {
-  final Function() onPressed;
+  final Function()? onPressed;
   final Widget icon;
   final bool visible;
   final double width;
@@ -687,13 +687,13 @@ class _FooterButton extends StatelessWidget {
   final bool roundedButtons;
 
   const _FooterButton({
-    Key key,
-    @required this.icon,
-    @required this.onPressed,
+    Key? key,
+    required this.icon,
+    required this.onPressed,
     this.visible = true,
     this.width = 45,
     this.bgColor = Colors.black,
-    @required this.roundedButtons,
+    required this.roundedButtons,
   })  : assert(icon != null),
         assert(visible != null),
         assert(roundedButtons != null),
@@ -712,7 +712,7 @@ class _FooterButton extends StatelessWidget {
         child: FloatingActionButton(
           child: icon,
           foregroundColor: Colors.white,
-          onPressed: onPressed == null ? null : () => onPressed(),
+          onPressed: onPressed == null ? null : () => onPressed!(),
           backgroundColor: bgColor,
         ),
       ));

lib/ui/screens/conversation_members_screen.dart

@@ -15,8 +15,8 @@ class ConversationMembersScreen extends StatefulWidget {
   final int convID;
 
   const ConversationMembersScreen({
-    Key key,
-    @required this.convID,
+    Key? key,
+    required this.convID,
   })  : assert(convID != null),
         super(key: key);
 
@@ -26,8 +26,8 @@ class ConversationMembersScreen extends StatefulWidget {
 }
 
 class _ConversationMembersScreenState extends State<ConversationMembersScreen> {
-  Conversation _conversation;
-  UsersList _members;
+  late Conversation _conversation;
+  late UsersList _members;
 
   Future<void> _refresh() async {
     _conversation =
@@ -38,28 +38,28 @@ class _ConversationMembersScreenState extends State<ConversationMembersScreen> {
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      appBar: AppBar(title: Text(tr("Conversation members"))),
+      appBar: AppBar(title: Text(tr("Conversation members")!)),
       body: AsyncScreenWidget(
         onReload: _refresh,
         onBuild: _buildMembersList,
         errorMessage:
-            tr("Could not load the list of members of this conversation!"),
+            tr("Could not load the list of members of this conversation!")!,
       ),
     );
   }
 
   Widget _buildMembersList() => ListView.builder(
         itemBuilder: _buildItem,
-        itemCount: _conversation.members.length,
+        itemCount: _conversation.members!.length,
       );
 
   Widget _buildItem(BuildContext context, int index) {
-    final member = _conversation.members[index];
+    final member = _conversation.members![index];
     final user = _members.getUser(member.userID);
     return ListTile(
       leading: AccountImageWidget(user: user),
       title: Text(user.displayName),
-      subtitle: Text(member.isAdmin ? tr("Admin") : tr("Member")),
+      subtitle: Text(member.isAdmin ? tr("Admin")! : tr("Member")!),
     );
   }
 }

lib/ui/screens/conversation_screen.dart

@@ -42,7 +42,7 @@ enum _OlderMessagesLevel { NONE, LOADING, NO_MORE_AVAILABLE }
 class ConversationScreen extends StatefulWidget {
   final int conversationID;
 
-  const ConversationScreen({Key key, this.conversationID})
+  const ConversationScreen({Key? key, required this.conversationID})
       : assert(conversationID != null),
         super(key: key);
 
@@ -56,8 +56,8 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
   final UsersHelper _usersHelper = UsersHelper();
 
   // Class members
-  Conversation _conversation;
-  ConversationMessagesList _messages;
+  late Conversation _conversation;
+  ConversationMessagesList? _messages;
   UsersList _usersInfo = UsersList();
   ErrorLevel _error = ErrorLevel.NONE;
   final _textFieldFocus = FocusNode();
@@ -66,21 +66,21 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
 
   bool _isSendingMessage = false;
   TextEditingController _textController = TextEditingController();
-  ScrollWatcher _scrollController;
+  ScrollWatcher? _scrollController;
   _OlderMessagesLevel _loadingOlderMessages = _OlderMessagesLevel.NONE;
 
   int _lastWritingEventSent = 0;
 
-  CancelToken _sendCancel;
-  double _sendProgress;
+  CancelToken? _sendCancel;
+  double? _sendProgress;
 
   String get textMessage => _textController.text;
 
   bool get _isMessageValid =>
       textMessage.length >=
-          ServerConfigurationHelper.config.conversationsPolicy.minMessageLen &&
+          ServerConfigurationHelper.config!.conversationsPolicy.minMessageLen &&
       textMessage.length <
-          ServerConfigurationHelper.config.conversationsPolicy.maxMessageLen;
+          ServerConfigurationHelper.config!.conversationsPolicy.maxMessageLen;
 
   showKeyboard() => _textFieldFocus.requestFocus();
 
@@ -179,14 +179,14 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
     this.listen<UpdatedConversationMessageEvent>((ev) async {
       if (ev.msg.convID == widget.conversationID) {
         await _conversationsHelper.saveMessage(ev.msg);
-        setState(() => _messages.replace(ev.msg));
+        setState(() => _messages!.replace(ev.msg));
       }
     });
 
     this.listen<DeletedConversationMessageEvent>((ev) async {
       if (ev.msg.convID == widget.conversationID) {
         await _conversationsHelper.removeMessage(ev.msg);
-        setState(() => _messages.removeMsg(ev.msg.id));
+        setState(() => _messages!.removeMsg(ev.msg.id));
       }
     });
 
@@ -216,7 +216,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
       //First, get the messages
       final messages = await _conversationsHelper.getNewMessages(
         conversationID: widget.conversationID,
-        lastMessageID: _messages == null ? 0 : _messages.lastMessageID,
+        lastMessageID: _messages == null ? 0 : _messages!.lastMessageID,
         online: online,
       );
 
@@ -235,14 +235,14 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
   Future<void> _loadOlderMessages() async {
     if (_loadingOlderMessages != _OlderMessagesLevel.NONE ||
         _messages == null ||
-        _messages.length == 0) return;
+        _messages!.length == 0) return;
     try {
       // Let's start to load older messages
       _setLoadingOlderMessagesState(_OlderMessagesLevel.LOADING);
 
       final messages = await _conversationsHelper.getOlderMessages(
           conversationID: widget.conversationID,
-          oldestMessagesID: _messages.firstMessageID);
+          oldestMessagesID: _messages!.firstMessageID);
 
       // Mark as not loading anymore
       _setLoadingOlderMessagesState(_OlderMessagesLevel.NONE);
@@ -280,14 +280,14 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
       if (_messages == null)
         _messages = messages;
       else
-        _messages.addAll(messages);
+        _messages!.addAll(messages);
 
       //Reverse the order of the messages (if required)
       if (messages.length > 0) {
-        _messages.sort();
-        final reverse = _messages.reversed;
+        _messages!.sort();
+        final Iterable<ConversationMessage> reverse = _messages!.reversed;
         _messages = ConversationMessagesList();
-        _messages.addAll(reverse);
+        _messages!.addAll(reverse);
       }
     });
 
@@ -300,20 +300,20 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
     try {
       final file = await showPickFileDialog(
         context: context,
-        maxFileSize: srvConfig.conversationsPolicy.filesMaxSize,
-        allowedMimeTypes: srvConfig.conversationsPolicy.allowedFilesType,
-        imageMaxWidth: srvConfig.conversationsPolicy.maxMessageImageWidth,
-        imageMaxHeight: srvConfig.conversationsPolicy.maxMessageImageHeight,
+        maxFileSize: srvConfig!.conversationsPolicy.filesMaxSize,
+        allowedMimeTypes: srvConfig!.conversationsPolicy.allowedFilesType,
+        imageMaxWidth: srvConfig!.conversationsPolicy.maxMessageImageWidth,
+        imageMaxHeight: srvConfig!.conversationsPolicy.maxMessageImageHeight,
       );
 
       if (file == null) return;
 
-      BytesFile thumbnail;
+      BytesFile? thumbnail;
 
-      if (isVideo(lookupMimeType(file.filename)))
+      if (isVideo(lookupMimeType(file.filename)!))
         thumbnail = await generateVideoThumbnail(
           videoFile: file,
-          maxWidth: srvConfig.conversationsPolicy.maxThumbnailWidth,
+          maxWidth: srvConfig!.conversationsPolicy.maxThumbnailWidth,
         );
 
       _sendCancel = CancelToken();
@@ -331,7 +331,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
       assert(res == SendMessageResult.SUCCESS);
     } catch (e, s) {
       logError(e, s);
-      showSimpleSnack(context, tr("Failed to send a file!"));
+      showSimpleSnack(context, tr("Failed to send a file!")!);
     }
 
     setState(() {
@@ -363,8 +363,8 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
         SnackBar(
           content: Text(
             result == SendMessageResult.MESSAGE_REJECTED
-                ? tr("Message rejected by the server!")
-                : tr("Could not send message!"),
+                ? tr("Message rejected by the server!")!
+                : tr("Could not send message!")!,
           ),
           duration: Duration(milliseconds: 500),
         ),
@@ -395,7 +395,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
   Widget _buildNoMessagesNotice() {
     return Expanded(
       child: Center(
-        child: Text(tr("There is no message yet in this conversation.")),
+        child: Text(tr("There is no message yet in this conversation.")!),
       ),
     );
   }
@@ -406,15 +406,15 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
         child: ListView.builder(
       controller: _scrollController,
       reverse: true,
-      itemCount: _messages.length,
+      itemCount: _messages!.length,
       itemBuilder: (c, i) => _buildMessageItem(i),
     ));
   }
 
   Widget _buildMessageItem(int msgIndex) {
-    final msg = _messages[msgIndex];
+    final msg = _messages![msgIndex];
     final nextMessage =
-        msgIndex + 1 < _messages.length ? _messages[msgIndex + 1] : null;
+        msgIndex + 1 < _messages!.length ? _messages![msgIndex + 1] : null;
 
     return Column(
       children: <Widget>[
@@ -427,7 +427,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
             ? Container(
                 alignment: Alignment.center,
                 child: ServerConversationMessageTile(
-                    message: msg.serverMessage, users: _usersInfo),
+                    message: msg.serverMessage!, users: _usersInfo),
               )
             : Container(
                 margin: EdgeInsets.symmetric(vertical: 5),
@@ -442,7 +442,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
   }
 
   Widget _buildSenderLayout(
-      ConversationMessage message, ConversationMessage previousMessage) {
+      ConversationMessage message, ConversationMessage? previousMessage) {
     final messageRadius = Radius.circular(10);
 
     return Container(
@@ -466,7 +466,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
   }
 
   Widget _buildReceiverLayout(
-      ConversationMessage message, ConversationMessage previousMessage) {
+      ConversationMessage message, ConversationMessage? previousMessage) {
     final messageRadius = Radius.circular(10);
 
     return Row(children: [
@@ -640,11 +640,11 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
               flex: 5,
             ),
             Spacer(flex: 1),
-            Text("${(_sendProgress * 100).toInt()}%"),
+            Text("${(_sendProgress! * 100).toInt()}%"),
             Spacer(flex: 1),
             OutlinedButton(
-              onPressed: () => _sendCancel.cancel(),
-              child: Text(tr("Cancel").toUpperCase()),
+              onPressed: () => _sendCancel!.cancel(),
+              child: Text(tr("Cancel")!.toUpperCase()),
             ),
             Spacer(flex: 1),
           ],
@@ -667,8 +667,8 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
               ? _buildLoadingOlderMessage()
               : null,
         ),
-        _messages.length == 0 ? _buildNoMessagesNotice() : _buildMessagesList(),
-        UserWritingInConvNotifier(convID: _conversation.id),
+        _messages!.length == 0 ? _buildNoMessagesNotice() : _buildMessagesList(),
+        UserWritingInConvNotifier(convID: _conversation.id!),
         _sendCancel != null ? _buildSendingWidget() : _buildSendMessageForm(),
         _showEmojiPicker ? _buildEmojiContainer() : Container(),
       ],
@@ -681,7 +681,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
       final t = time();
 
       if (t - _lastWritingEventSent <
-          srvConfig.conversationsPolicy.writingEventInterval) return;
+          srvConfig!.conversationsPolicy.writingEventInterval) return;
 
       _lastWritingEventSent = t;
       await ConversationsHelper.sendWritingEvent(_conversation.id);
@@ -692,7 +692,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
 
   /// Request message statistics
   void _requestMessageStats(ConversationMessage message) async {
-    MainController.of(context)
+    MainController.of(context)!
         .openConversationMessageStats(_conversation, message);
   }
 
@@ -700,20 +700,20 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
   Future<void> _updateMessage(ConversationMessage message) async {
     final newContent = await askUserString(
       context: context,
-      title: tr("Update message"),
-      message: tr("Please enter new message content:"),
-      defaultValue: message.message.content,
-      hint: tr("New message"),
+      title: tr("Update message")!,
+      message: tr("Please enter new message content:")!,
+      defaultValue: message.message.content!,
+      hint: tr("New message")!,
       minLength:
-          ServerConfigurationHelper.config.conversationsPolicy.minMessageLen,
+          ServerConfigurationHelper.config!.conversationsPolicy.minMessageLen,
       maxLength:
-          ServerConfigurationHelper.config.conversationsPolicy.maxMessageLen,
+          ServerConfigurationHelper.config!.conversationsPolicy.maxMessageLen,
     );
 
     if (newContent == null) return;
 
     if (!await _conversationsHelper.updateMessage(message.id, newContent)) {
-      showSimpleSnack(context, tr("Could not update message content!"));
+      showSimpleSnack(context, tr("Could not update message content!")!);
       return;
     }
   }
@@ -723,21 +723,21 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
     final choice = await showDialog<bool>(
       context: context,
       builder: (c) => AlertDialog(
-        title: Text(tr("Confirm deletion")),
+        title: Text(tr("Confirm deletion")!),
         content: Text(
-          tr("Do you really want to delete this message ? The operation can not be cancelled !"),
+          tr("Do you really want to delete this message ? The operation can not be cancelled !")!,
           textAlign: TextAlign.justify,
         ),
         actions: <Widget>[
           TextButton(
             child: Text(
-              tr("Cancel").toUpperCase(),
+              tr("Cancel")!.toUpperCase(),
             ),
             onPressed: () => Navigator.pop(c, false),
           ),
           TextButton(
             child: Text(
-              tr("Confirm").toUpperCase(),
+              tr("Confirm")!.toUpperCase(),
               style: TextStyle(color: Colors.red),
             ),
             onPressed: () => Navigator.pop(c, true),
@@ -750,6 +750,6 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
 
     // Execute the request
     if (!await _conversationsHelper.deleteMessage(message.id))
-      showSimpleSnack(context, tr("Could not delete conversation message!"));
+      showSimpleSnack(context, tr("Could not delete conversation message!")!);
   }
 }

lib/ui/screens/conversations_list_screen.dart

@@ -21,10 +21,10 @@ import 'package:flutter/material.dart';
 
 class ConversationsListScreen extends StatefulWidget {
   final bool useSmallFAB;
-  final Function() onOpen;
+  final Function()? onOpen;
 
   const ConversationsListScreen({
-    Key key,
+    Key? key,
     this.useSmallFAB = false,
     this.onOpen,
   })  : assert(useSmallFAB != null),
@@ -37,9 +37,9 @@ class ConversationsListScreen extends StatefulWidget {
 class _ConversationScreenState extends SafeState<ConversationsListScreen> {
   final ConversationsHelper _conversationsHelper = ConversationsHelper();
   final UsersHelper _usersHelper = UsersHelper();
-  ConversationsList _list;
-  UsersList _users;
-  GroupsList _groups;
+  ConversationsList? _list;
+  late UsersList _users;
+  GroupsList? _groups;
   LoadErrorLevel _error = LoadErrorLevel.NONE;
   final GlobalKey<RefreshIndicatorState> _refreshIndicatorKey =
       GlobalKey<RefreshIndicatorState>();
@@ -49,7 +49,7 @@ class _ConversationScreenState extends SafeState<ConversationsListScreen> {
     super.initState();
 
     this.listen<NewNumberUnreadConversations>(
-        (d) => _refreshIndicatorKey.currentState.show());
+        (d) => _refreshIndicatorKey.currentState!.show());
   }
 
   @override
@@ -94,9 +94,9 @@ class _ConversationScreenState extends SafeState<ConversationsListScreen> {
       tr("Could not retrieve the list of conversations!"),
       actions: <Widget>[
         TextButton(
-          onPressed: () => _refreshIndicatorKey.currentState.show(),
+          onPressed: () => _refreshIndicatorKey.currentState!.show(),
           child: Text(
-            tr("Retry").toUpperCase(),
+            tr("Retry")!.toUpperCase(),
             style: TextStyle(
               color: Colors.white,
             ),
@@ -108,23 +108,23 @@ class _ConversationScreenState extends SafeState<ConversationsListScreen> {
 
   /// Open a conversation
   void _openConversation(Conversation conv) {
-    MainController.of(context).openConversation(conv);
-    if (widget.onOpen != null) widget.onOpen();
+    MainController.of(context)!.openConversation(conv);
+    if (widget.onOpen != null) widget.onOpen!();
   }
 
   /// Create a new conversation
   void _createConversation() {
-    MainController.of(context).push(
+    MainController.of(context)!.push(
       CreateConversationScreen(),
       canShowAsDialog: true,
       hideNavBar: true,
     );
-    if (widget.onOpen != null) widget.onOpen();
+    if (widget.onOpen != null) widget.onOpen!();
   }
 
   /// Handle conversations updated requests
   void _updateConversation(Conversation conversation) {
-    MainController.of(context).openConversationSettingsRoute(conversation);
+    MainController.of(context)!.openConversationSettingsRoute(conversation);
   }
 
   /// Handle conversation deletion request
@@ -153,7 +153,7 @@ class _ConversationScreenState extends SafeState<ConversationsListScreen> {
     } catch (e, s) {
       print("Failed to leave conversation! $e => $s");
       ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text(tr("Could not leave the conversation!"))));
+          SnackBar(content: Text(tr("Could not leave the conversation!")!)));
     }
 
     // Reload the list of conversations
@@ -181,11 +181,11 @@ class _ConversationScreenState extends SafeState<ConversationsListScreen> {
                   physics: AlwaysScrollableScrollPhysics(),
                   controller: ScrollController(),
                   itemBuilder: (context, index) {
-                    if (_list[index].isGroupConversation &&
-                        !_list[index].following) return Container();
+                    if (_list![index].isGroupConversation &&
+                        !_list![index].following) return Container();
 
                     return ConversationTile(
-                      conversation: _list.elementAt(index),
+                      conversation: _list!.elementAt(index),
                       usersList: _users,
                       groupsList: _groups,
                       onOpen: (c) {
@@ -195,7 +195,7 @@ class _ConversationScreenState extends SafeState<ConversationsListScreen> {
                       onRequestLeave: _requestLeaveConversation,
                     );
                   },
-                  itemCount: _list.length,
+                  itemCount: _list!.length,
                 ),
               ),
             ),

lib/ui/screens/friends_list_screen.dart

@@ -22,7 +22,7 @@ enum _ErrorsLevel { NONE, MINOR, MAJOR }
 class FriendsListScreen extends StatefulWidget {
   final bool showAppBar;
 
-  const FriendsListScreen({Key key, this.showAppBar = true}) : super(key: key);
+  const FriendsListScreen({Key? key, this.showAppBar = true}) : super(key: key);
 
   @override
   State<StatefulWidget> createState() => _FriendsListScreenState();
@@ -35,8 +35,8 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
 
   /// Widget members
   _ErrorsLevel _error = _ErrorsLevel.NONE;
-  FriendsList _friendsList;
-  UsersList _usersInfo;
+  FriendsList? _friendsList;
+  late UsersList _usersInfo;
   GlobalKey<RefreshIndicatorState> _refreshIndicatorKey =
       GlobalKey<RefreshIndicatorState>();
 
@@ -61,7 +61,7 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
 
   /// Refresh the list of friends
   Future<void> _refreshList() async {
-    await _refreshIndicatorKey.currentState.show();
+    await _refreshIndicatorKey.currentState!.show();
   }
 
   /// Load the list of friends
@@ -72,7 +72,7 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
     final list = await _friendsHelper.getList(online: online);
 
     // Check if there is no cache yet
-    if (!online && list.isEmpty) return;
+    if (!online && list!.isEmpty) return;
 
     // Check for errors
     if (list == null) return _gotError();
@@ -98,7 +98,7 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
           TextButton(
             onPressed: _refreshList,
             child: Text(
-              tr("Retry").toUpperCase(),
+              tr("Retry")!.toUpperCase(),
               style: TextStyle(color: Colors.white),
             ),
           ),
@@ -109,7 +109,7 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
   Widget build(BuildContext context) => Scaffold(
         appBar: widget.showAppBar
             ? AppBar(
-                title: Text(tr("Your friends list")),
+                title: Text(tr("Your friends list")!),
               )
             : null,
         body: _buildBody(),
@@ -131,18 +131,18 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
             onRefresh: () => _loadList(true),
             child: ListView.builder(
                 physics: AlwaysScrollableScrollPhysics(),
-                itemCount: _friendsList.length,
-                itemBuilder: (c, i) => _friendsList[i].accepted
+                itemCount: _friendsList!.length,
+                itemBuilder: (c, i) => _friendsList![i].accepted
                     ? AcceptedFriendTile(
-                        friend: _friendsList[i],
-                        user: _usersInfo.getUser(_friendsList[i].id),
+                        friend: _friendsList![i],
+                        user: _usersInfo.getUser(_friendsList![i].id),
                         onOpenPrivateConversation: _openPrivateConversation,
                         onSetFollowing: _setFollowingFriend,
                         onRequestDelete: _deleteFriend,
                       )
                     : PendingFriendTile(
-                        friend: _friendsList[i],
-                        user: _usersInfo.getUser(_friendsList[i].id),
+                        friend: _friendsList![i],
+                        user: _usersInfo.getUser(_friendsList![i].id),
                         onRespond: _respondRequest,
                       )),
           ),
@@ -154,7 +154,7 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
   /// Respond to friendship request
   Future<void> _respondRequest(Friend f, bool accept) async {
     if (!await _friendsHelper.respondRequest(f.id, accept))
-      showSimpleSnack(context, tr("Could not respond to friendship request!"));
+      showSimpleSnack(context, tr("Could not respond to friendship request!")!);
 
     // Load the list of friends again
     _refreshList();
@@ -163,7 +163,7 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
   /// Update following status of a friend
   Future<void> _setFollowingFriend(Friend friend, bool follow) async {
     if (!await _friendsHelper.setFollowing(friend.id, follow))
-      showSimpleSnack(context, tr("Could not update following status!"));
+      showSimpleSnack(context, tr("Could not update following status!")!);
 
     _refreshList();
   }
@@ -173,18 +173,18 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
     final choice = await showDialog<bool>(
       context: context,
       builder: (b) => AlertDialog(
-        title: Text(tr("Delete friend")),
+        title: Text(tr("Delete friend")!),
         content: Text(tr(
-            "Are you sure do you want to remove this friend from your list of friends ? A friendship request will have to be sent to get this user back to your list!")),
+            "Are you sure do you want to remove this friend from your list of friends ? A friendship request will have to be sent to get this user back to your list!")!),
         actions: <Widget>[
           TextButton(
             onPressed: () => Navigator.pop(context, false),
-            child: Text(tr("Cancel").toUpperCase()),
+            child: Text(tr("Cancel")!.toUpperCase()),
           ),
           TextButton(
             onPressed: () => Navigator.pop(context, true),
             child: Text(
-              tr("Confirm").toUpperCase(),
+              tr("Confirm")!.toUpperCase(),
               style: TextStyle(color: Colors.red),
             ),
           ),
@@ -197,7 +197,7 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
     // Forward the request to the server
     if (!await _friendsHelper.removeFriend(f.id))
       showSimpleSnack(
-          context, tr("Could not delete this person from your friends list!"));
+          context, tr("Could not delete this person from your friends list!")!);
 
     // Refresh list
     _refreshList();

lib/ui/screens/group_access_denied_screen.dart

@@ -16,9 +16,9 @@ class GroupAccessDeniedScreen extends StatefulWidget {
   final Function() onMembershipAcquired;
 
   const GroupAccessDeniedScreen({
-    Key key,
-    @required this.groupID,
-    @required this.onMembershipAcquired,
+    Key? key,
+    required this.groupID,
+    required this.onMembershipAcquired,
   })  : assert(groupID != null),
         assert(onMembershipAcquired != null),
         super(key: key);
@@ -29,7 +29,7 @@ class GroupAccessDeniedScreen extends StatefulWidget {
 }
 
 class _GroupAccessDeniedScreenState extends SafeState<GroupAccessDeniedScreen> {
-  Group _group;
+  Group? _group;
 
   bool error = false;
 
@@ -45,7 +45,7 @@ class _GroupAccessDeniedScreenState extends SafeState<GroupAccessDeniedScreen> {
       return buildErrorCard(tr("Could not get basic group information!"),
           actions: [
             MaterialButton(
-              child: Text(tr("Try again").toUpperCase()),
+              child: Text(tr("Try again")!.toUpperCase()),
               onPressed: () => this._refresh(),
             )
           ]);
@@ -61,20 +61,20 @@ class _GroupAccessDeniedScreenState extends SafeState<GroupAccessDeniedScreen> {
             Spacer(
               flex: 5,
             ),
-            GroupIcon(group: _group),
+            GroupIcon(group: _group!),
             Spacer(),
             Text(
-              _group.displayName,
+              _group!.displayName,
               style: TextStyle(fontSize: 20),
             ),
             Spacer(),
             Text(
-              tr("A registration is required to access this group page."),
+              tr("A registration is required to access this group page.")!,
               textAlign: TextAlign.center,
             ),
             Spacer(),
             GroupMembershipWidget(
-              group: _group,
+              group: _group!,
               onUpdated: () => this._refresh(),
               onError: () => this._refresh(),
             ),

lib/ui/screens/group_screen.dart

@@ -12,11 +12,11 @@ import 'package:flutter/material.dart';
 
 class GroupPageScreen extends StatefulWidget {
   final int groupID;
-  final int conversationID;
+  final int? conversationID;
 
   const GroupPageScreen({
-    Key key,
-    @required this.groupID,
+    Key? key,
+    required this.groupID,
     this.conversationID,
   })  : assert(groupID != null),
         super(key: key);
@@ -28,7 +28,7 @@ class GroupPageScreen extends StatefulWidget {
 class _GroupPageScreenState extends SafeState<GroupPageScreen> {
   int get groupID => widget.groupID;
 
-  GetAdvancedInfoResult _getGroupResult;
+  GetAdvancedInfoResult? _getGroupResult;
   var error = false;
 
   @override
@@ -44,7 +44,7 @@ class _GroupPageScreenState extends SafeState<GroupPageScreen> {
           actions: [
             MaterialButton(
               onPressed: () => _refreshPage(),
-              child: Text(tr("Try again").toUpperCase()),
+              child: Text(tr("Try again")!.toUpperCase()),
             )
           ]);
 
@@ -52,7 +52,7 @@ class _GroupPageScreenState extends SafeState<GroupPageScreen> {
     if (_getGroupResult == null) return buildCenteredProgressBar();
 
     // Check if access to the group was denied
-    if (_getGroupResult.status == GetAdvancedInfoStatus.ACCESS_DENIED)
+    if (_getGroupResult!.status == GetAdvancedInfoStatus.ACCESS_DENIED)
       return GroupAccessDeniedScreen(
         groupID: groupID,
         onMembershipAcquired: () => _refreshPage(),
@@ -60,7 +60,7 @@ class _GroupPageScreenState extends SafeState<GroupPageScreen> {
 
     // Now we can show group page
     return AuthorizedGroupPageScreen(
-      advancedGroupInfo: _getGroupResult.info,
+      advancedGroupInfo: _getGroupResult!.info!,
       conversationID: widget.conversationID,
       needRefresh: () => _refreshPage(),
     );

lib/ui/screens/group_sections/about_group_section.dart

@@ -13,8 +13,8 @@ class AboutGroupSection extends StatelessWidget {
   final AdvancedGroupInfo group;
 
   const AboutGroupSection({
-    Key key,
-    @required this.group,
+    Key? key,
+    required this.group,
   })  : assert(group != null),
         super(key: key);
 
@@ -25,7 +25,7 @@ class AboutGroupSection extends StatelessWidget {
           group.hasURL
               ? ListTile(
                   leading: Icon(Icons.link),
-                  title: Text(tr("URL")),
+                  title: Text(tr("URL")!),
                   subtitle: Text(group.url),
                   onTap: () => launch(group.url),
                 )
@@ -35,7 +35,7 @@ class AboutGroupSection extends StatelessWidget {
           group.hasDescription
               ? ListTile(
                   leading: Icon(Icons.note),
-                  title: Text(tr("Description")),
+                  title: Text(tr("Description")!),
                   subtitle: Text(group.description),
                 )
               : Container(),
@@ -44,64 +44,64 @@ class AboutGroupSection extends StatelessWidget {
           ListTile(
             leading: Icon(Icons.access_time),
             title: Text("Created"),
-            subtitle: Text(diffTimeFromNowToStr(group.timeCreate)),
+            subtitle: Text(diffTimeFromNowToStr(group.timeCreate!)!),
           ),
 
           // Number of members
           ListTile(
             leading: Icon(Icons.group),
-            title: Text(tr("Members")),
+            title: Text(tr("Members")!),
             subtitle: Text(
-                tr("%1% members", args: {"1": group.numberMembers.toString()})),
+                tr("%1% members", args: {"1": group.numberMembers.toString()})!),
           ),
 
           // Who can create posts
           ListTile(
             leading: Icon(Icons.add),
-            title: Text(tr("Who can create posts")),
+            title: Text(tr("Who can create posts")!),
             subtitle: Text(
                 group.postCreationLevel == GroupPostCreationLevel.MEMBERS
-                    ? tr("Every members")
-                    : tr("Only moderators and administrators")),
+                    ? tr("Every members")!
+                    : tr("Only moderators and administrators")!),
           ),
 
           // Registration process
           ListTile(
             leading: Icon(Icons.login),
-            title: Text(tr("Registration process")),
+            title: Text(tr("Registration process")!),
             subtitle: Text(group.registrationLevel ==
                     GroupRegistrationLevel.CLOSED
-                ? tr("On invitation only")
+                ? tr("On invitation only")!
                 : (group.registrationLevel == GroupRegistrationLevel.MODERATED
-                    ? tr("A moderator has to approve requests")
-                    : tr("Anyone can join the group without approval"))),
+                    ? tr("A moderator has to approve requests")!
+                    : tr("Anyone can join the group without approval")!)),
           ),
 
           // Group visibility
           ListTile(
             leading: Icon(Icons.remove_red_eye),
-            title: Text(tr("Visibility")),
+            title: Text(tr("Visibility")!),
             subtitle: Text(group.visibilityLevel == GroupVisibilityLevel.SECRETE
-                ? tr("Secrete group")
+                ? tr("Secrete group")!
                 : (group.visibilityLevel == GroupVisibilityLevel.PRIVATE
-                    ? tr("Private group")
-                    : tr("Open group"))),
+                    ? tr("Private group")!
+                    : tr("Open group")!)),
           ),
 
           // Group members visibility
           ListTile(
             leading: Icon(Icons.remove_red_eye),
-            title: Text(tr("Members list visibility")),
+            title: Text(tr("Members list visibility")!),
             subtitle:
-                Text(group.isMembersListPublic ? tr("Public") : tr("Private")),
+                Text(group.isMembersListPublic! ? tr("Public")! : tr("Private")!),
           ),
 
           group.isForezGroup
               ? // Group members visibility
               ListTile(
                   leading: Icon(Icons.info_outline),
-                  title: Text(tr("Forez group")),
-                  subtitle: Text(tr("Forez special features enabled")),
+                  title: Text(tr("Forez group")!),
+                  subtitle: Text(tr("Forez special features enabled")!),
                 )
               : Container(),
         ],

lib/ui/screens/group_sections/forez_presence_section.dart

@@ -16,8 +16,8 @@ class ForezPresenceSection extends StatefulWidget {
   final int groupID;
 
   const ForezPresenceSection({
-    Key key,
-    @required this.groupID,
+    Key? key,
+    required this.groupID,
   })  : assert(groupID != null),
         super(key: key);
 
@@ -26,17 +26,17 @@ class ForezPresenceSection extends StatefulWidget {
 }
 
 class _ForezPresenceSectionState extends State<ForezPresenceSection> {
-  PresenceSet _presences;
-  UsersList _users;
+  PresenceSet? _presences;
+  late UsersList _users;
   DateTime _currentDay = DateTime.now();
 
-  List<int> get _currentListOfUsers => _presences.getUsersAtDate(_currentDay);
+  List<int> get _currentListOfUsers => _presences!.getUsersAtDate(_currentDay);
 
   Future<void> _refresh() async {
     await ForezPresenceHelper.refreshCache(widget.groupID);
 
     _presences = await ForezPresenceHelper.getAll(widget.groupID);
-    _users = await UsersHelper().getList(_presences.usersID);
+    _users = await UsersHelper().getList(_presences!.usersID);
   }
 
   @override
@@ -71,7 +71,7 @@ class _ForezPresenceSectionState extends State<ForezPresenceSection> {
   }
 
   Widget _buildCalendar() => PresenceCalendarWidget(
-        presenceSet: _presences,
+        presenceSet: _presences!,
         mode: CalendarDisplayMode.MULTIPLE_USERS,
         selectedDay: _currentDay,
         onDayClicked: _selectDay,

lib/ui/screens/group_sections/group_conversation_section.dart

@@ -12,8 +12,8 @@ class GroupConversationSection extends StatelessWidget {
   final Conversation conv;
 
   const GroupConversationSection({
-    Key key,
-    @required this.conv,
+    Key? key,
+    required this.conv,
   })  : assert(conv != null),
         super(key: key);
 
@@ -21,7 +21,7 @@ class GroupConversationSection extends StatelessWidget {
   Widget build(BuildContext context) => Stack(
         children: [
           ConversationScreen(
-            conversationID: conv.id,
+            conversationID: conv.id!,
           ),
           Positioned(
             right: 1.0,
@@ -31,12 +31,12 @@ class GroupConversationSection extends StatelessWidget {
                     ? IconButton(
                         icon: Icon(Icons.phone),
                         onPressed: () =>
-                            MainController.of(context).startCall(conv.id),
+                            MainController.of(context)!.startCall(conv.id!),
                       )
                     : Container(),
                 IconButton(
                   icon: Icon(Icons.settings),
-                  onPressed: () => MainController.of(context)
+                  onPressed: () => MainController.of(context)!
                       .openConversationSettingsRoute(conv),
                 ),
               ],

lib/ui/screens/group_sections/group_members_screen.dart

@@ -21,7 +21,7 @@ import 'package:flutter/material.dart';
 class GroupMembersSection extends StatefulWidget {
   final int groupID;
 
-  const GroupMembersSection({Key key, this.groupID})
+  const GroupMembersSection({Key? key, required this.groupID})
       : assert(groupID != null),
         super(key: key);
 
@@ -31,9 +31,9 @@ class GroupMembersSection extends StatefulWidget {
 
 class _GroupMembersSectionState extends State<GroupMembersSection> {
   final _key = GlobalKey<AsyncScreenWidgetState>();
-  Group _group;
-  GroupMembersList _members;
-  UsersList _users;
+  late Group _group;
+  late GroupMembersList _members;
+  late UsersList _users;
 
   Future<void> _refresh() async {
     final group = await GroupsHelper().getSingle(widget.groupID, force: true);
@@ -50,7 +50,7 @@ class _GroupMembersSectionState extends State<GroupMembersSection> {
         key: _key,
         onReload: _refresh,
         onBuild: _buildBodyContent,
-        errorMessage: tr("Could not load the list of members of this group!"),
+        errorMessage: tr("Could not load the list of members of this group!")!,
         showOldDataWhileUpdating: true,
       );
 
@@ -70,7 +70,7 @@ class _GroupMembersSectionState extends State<GroupMembersSection> {
       group: _group,
       membership: membership,
       user: user,
-      onUpdated: () => _key.currentState.refresh(),
+      onUpdated: () => _key.currentState!.refresh(),
     );
   }
 
@@ -93,40 +93,40 @@ class _GroupMembersSectionState extends State<GroupMembersSection> {
       await GroupsHelper.sendInvitation(widget.groupID, userID);
     } catch (e, s) {
       print("Could not invite a user! $e\n$s");
-      showSimpleSnack(context, tr("Could not invite a user!"));
+      showSimpleSnack(context, tr("Could not invite a user!")!);
     }
 
-    _key.currentState.refresh();
+    _key.currentState!.refresh();
   }
 }
 
 List<MultiChoiceEntry<GroupMembershipLevel>> get _membershipLevels => [
       MultiChoiceEntry(
           id: GroupMembershipLevel.ADMINISTRATOR,
-          title: tr("Administrator"),
+          title: tr("Administrator")!,
           subtitle: tr("Can change members privileges and group settings")),
       MultiChoiceEntry(
           id: GroupMembershipLevel.MODERATOR,
-          title: tr("Moderator"),
+          title: tr("Moderator")!,
           subtitle: tr(
               "Can always create posts, invite users and respond to membership request")),
       MultiChoiceEntry(
           id: GroupMembershipLevel.MEMBER,
-          title: tr("Member"),
+          title: tr("Member")!,
           subtitle: tr("Can access to all group posts")),
       MultiChoiceEntry(
         id: GroupMembershipLevel.PENDING,
-        title: tr("Requested"),
+        title: tr("Requested")!,
         hidden: true,
       ),
       MultiChoiceEntry(
         id: GroupMembershipLevel.INVITED,
-        title: tr("Invited"),
+        title: tr("Invited")!,
         hidden: true,
       ),
       MultiChoiceEntry(
         id: GroupMembershipLevel.VISITOR,
-        title: tr("Visitor"),
+        title: tr("Visitor")!,
         hidden: true,
       ),
     ];
@@ -138,11 +138,11 @@ class _GroupMembershipTile extends StatefulWidget {
   final void Function() onUpdated;
 
   const _GroupMembershipTile({
-    Key key,
-    @required this.group,
-    @required this.membership,
-    @required this.user,
-    @required this.onUpdated,
+    Key? key,
+    required this.group,
+    required this.membership,
+    required this.user,
+    required this.onUpdated,
   })  : assert(group != null),
         assert(membership != null),
         assert(user != null),
@@ -176,7 +176,7 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
     );
   }
 
-  Widget _buildTrailing() {
+  Widget? _buildTrailing() {
     switch (widget.membership.level) {
       case GroupMembershipLevel.ADMINISTRATOR:
       case GroupMembershipLevel.MODERATOR:
@@ -205,14 +205,14 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
       itemBuilder: (c) => [
         // Change membership level
         PopupMenuItem(
-          child: Text(tr("Change level")),
+          child: Text(tr("Change level")!),
           enabled: !_isCurrentUser && widget.group.isAdmin,
           value: _MemberMenuOptions.CHANGE_LEVEL,
         ),
 
         // Remove membership
         PopupMenuItem(
-          child: Text(tr("Remove")),
+          child: Text(tr("Remove")!),
           value: _MemberMenuOptions.DELETE,
           enabled: !_isCurrentUser,
         ),
@@ -247,7 +247,7 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
       await GroupsHelper.setNewLevel(groupID, memberID, newLevel);
     } catch (e, s) {
       print("Could not change group membership level! $e\n$s");
-      showSimpleSnack(context, tr("Could not change group membership level!"));
+      showSimpleSnack(context, tr("Could not change group membership level!")!);
     }
 
     widget.onUpdated();
@@ -263,7 +263,7 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
       await GroupsHelper.removeMemberFromGroup(groupID, memberID);
     } catch (e, s) {
       print("Could not remove membership! $e\n$s");
-      showSimpleSnack(context, tr("Could not remove this membership!"));
+      showSimpleSnack(context, tr("Could not remove this membership!")!);
     }
 
     widget.onUpdated();
@@ -272,7 +272,7 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
   Widget _buildInvitedCase() {
     return MaterialButton(
       onPressed: _cancelMembership,
-      child: Text(tr("Cancel").toUpperCase()),
+      child: Text(tr("Cancel")!.toUpperCase()),
       textColor: Colors.red,
     );
   }
@@ -282,7 +282,7 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
       await GroupsHelper.cancelInvitation(groupID, memberID);
     } catch (e, s) {
       print("Could not cancel invitation! $e\n$s");
-      showSimpleSnack(context, tr("Could not cancel invitation!"));
+      showSimpleSnack(context, tr("Could not cancel invitation!")!);
     }
 
     widget.onUpdated();
@@ -294,12 +294,12 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
       children: <Widget>[
         MaterialButton(
           onPressed: () => _respondRequest(false),
-          child: Text(tr("Reject").toUpperCase()),
+          child: Text(tr("Reject")!.toUpperCase()),
           textColor: Colors.red,
         ),
         MaterialButton(
           onPressed: () => _respondRequest(true),
-          child: Text(tr("Accept").toUpperCase()),
+          child: Text(tr("Accept")!.toUpperCase()),
           textColor: Colors.green,
         )
       ],
@@ -311,7 +311,7 @@ class __GroupMembershipTileState extends State<_GroupMembershipTile> {
       await GroupsHelper.respondRequest(groupID, memberID, accept);
     } catch (e, s) {
       print("Could not respond to membership request! $e\n$s");
-      showSimpleSnack(context, tr("Could not respond to membership request!"));
+      showSimpleSnack(context, tr("Could not respond to membership request!")!);
     }
 
     widget.onUpdated();

lib/ui/screens/group_sections/group_posts_section.dart

@@ -12,8 +12,8 @@ class GroupPostsSection extends StatefulWidget {
   final AdvancedGroupInfo group;
 
   const GroupPostsSection({
-    Key key,
-    @required this.group,
+    Key? key,
+    required this.group,
   })  : assert(group != null),
         super(key: key);
 
@@ -31,7 +31,7 @@ class _GroupPostsSectionState extends State<GroupPostsSection> {
     return PostCreateFormWidget(
       postTarget: PostTarget.GROUP_PAGE,
       targetID: widget.group.id,
-      onCreated: () => _postsKey.currentState.loadPostsList(getOlder: false),
+      onCreated: () => _postsKey.currentState!.loadPostsList(getOlder: false),
     );
   }
 

lib/ui/screens/group_settings_screen.dart

@@ -34,7 +34,7 @@ import 'package:flutter_settings_ui/flutter_settings_ui.dart';
 class GroupSettingsScreen extends StatefulWidget {
   final int groupID;
 
-  const GroupSettingsScreen({Key key, @required this.groupID})
+  const GroupSettingsScreen({Key? key, required this.groupID})
       : assert(groupID != null),
         super(key: key);
 
@@ -43,7 +43,7 @@ class GroupSettingsScreen extends StatefulWidget {
 }
 
 class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
-  AdvancedGroupInfo _groupSettings;
+  AdvancedGroupInfo? _groupSettings;
 
   final _key = GlobalKey<AsyncScreenWidgetState>();
 
@@ -53,13 +53,13 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
 
   Future<void> _updateSettings() async {
     try {
-      await GroupsHelper.setSettings(_groupSettings);
+      await GroupsHelper.setSettings(_groupSettings!);
     } catch (e, stack) {
       print("Could not update group settings! $e\n$stack");
-      showSimpleSnack(context, tr("Could not update group settings!"));
+      showSimpleSnack(context, tr("Could not update group settings!")!);
     }
 
-    _key.currentState.refresh();
+    _key.currentState!.refresh();
   }
 
   @override
@@ -67,7 +67,7 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
     return Scaffold(
       appBar: AppBar(
         leading: ComunicBackButton(),
-        title: Text(tr("Group settings")),
+        title: Text(tr("Group settings")!),
       ),
       body: _buildBody(),
     );
@@ -78,7 +78,7 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
       key: _key,
       onReload: _refresh,
       onBuild: _buildContent,
-      errorMessage: tr("Could not get group settings!"),
+      errorMessage: tr("Could not get group settings!")!,
       showOldDataWhileUpdating: true,
     );
   }
@@ -96,65 +96,65 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
     );
   }
 
-  Widget _buildGeneralSection() {
+  SettingsSection _buildGeneralSection() {
     return SettingsSection(
       title: tr("General information"),
       tiles: [
         // Group ID
         SettingsTile(
           title: tr("Group ID"),
-          subtitle: _groupSettings.id.toString(),
+          subtitle: _groupSettings!.id.toString(),
         ),
 
         // Group name
         TextEditSettingsTile(
-            title: tr("Group name"),
-            currValue: _groupSettings.name,
+            title: tr("Group name")!,
+            currValue: _groupSettings!.name,
             onChanged: (s) {
-              _groupSettings.name = s;
+              _groupSettings!.name = s;
               _updateSettings();
             }),
 
         // Group virtual directory
         SettingsTile(
           title: tr("Virtual directory (optional)"),
-          subtitle: _groupSettings.virtualDirectory,
+          subtitle: _groupSettings!.virtualDirectory,
           onPressed: (_) async {
             final newDir = await showVirtualDirectoryDialog(
               context: context,
-              initialDirectory: _groupSettings.virtualDirectory,
-              id: _groupSettings.id,
+              initialDirectory: _groupSettings!.virtualDirectory,
+              id: _groupSettings!.id,
               type: VirtualDirectoryTargetType.GROUP,
             );
 
             if (newDir == null) return;
 
-            _groupSettings.virtualDirectory = newDir;
+            _groupSettings!.virtualDirectory = newDir;
             _updateSettings();
           },
         ),
 
         // Group URL
         TextEditSettingsTile(
-          title: tr("Group URL (optional)"),
-          currValue: _groupSettings.url,
+          title: tr("Group URL (optional)")!,
+          currValue: _groupSettings!.url,
           checkInput: validateUrl,
           allowEmptyValues: true,
           onChanged: (s) {
-            _groupSettings.url = s;
+            _groupSettings!.url = s;
             _updateSettings();
           },
         ),
 
         // Group description
         TextEditSettingsTile(
-            title: tr("Group description (optional)"),
-            currValue: _groupSettings.description,
+            title: tr("Group description (optional)")!,
+            currValue: _groupSettings!.description,
             maxLines: 3,
             maxLength: 255,
             allowEmptyValues: true,
             onChanged: (s) {
-              _groupSettings.description = s;
+              _groupSettings!.description = s;
               _updateSettings();
             }),
       ],
@@ -164,18 +164,18 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
   List<MultiChoiceEntry<GroupVisibilityLevel>> get _visibilityLevels => [
         MultiChoiceEntry(
           id: GroupVisibilityLevel.OPEN,
-          title: tr("Open group"),
+          title: tr("Open group")!,
           subtitle:
               tr("Group information & public posts are available to everyone."),
         ),
         MultiChoiceEntry(
           id: GroupVisibilityLevel.PRIVATE,
-          title: tr("Private group"),
+          title: tr("Private group")!,
           subtitle: tr("The group is accessible to accepted members only."),
         ),
         MultiChoiceEntry(
           id: GroupVisibilityLevel.SECRETE,
-          title: tr("Secrete group"),
+          title: tr("Secrete group")!,
           subtitle: tr("The group is visible only to invited members."),
         ),
       ];
@@ -183,19 +183,19 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
   List<MultiChoiceEntry<GroupRegistrationLevel>> get _registrationLevels => [
         MultiChoiceEntry(
           id: GroupRegistrationLevel.OPEN,
-          title: tr("Open registration"),
+          title: tr("Open registration")!,
           subtitle: tr(
               "Everyone can choose to join the group without moderator approval"),
         ),
         MultiChoiceEntry(
           id: GroupRegistrationLevel.MODERATED,
-          title: tr("Moderated registration"),
+          title: tr("Moderated registration")!,
           subtitle: tr(
               "Everyone can request a membership, but a moderator review the request"),
         ),
         MultiChoiceEntry(
           id: GroupRegistrationLevel.CLOSED,
-          title: tr("Closed registration"),
+          title: tr("Closed registration")!,
           subtitle: tr(
               "The only way to join the group is to be invited by a moderator"),
         ),
@@ -204,48 +204,48 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
   List<MultiChoiceEntry<GroupPostCreationLevel>> get _postsCreationLevels => [
         MultiChoiceEntry(
           id: GroupPostCreationLevel.MEMBERS,
-          title: tr("All members"),
+          title: tr("All members")!,
           subtitle:
               tr("All the members of the group can create posts on the group"),
         ),
         MultiChoiceEntry(
           id: GroupPostCreationLevel.MODERATORS,
-          title: tr("Moderators only"),
+          title: tr("Moderators only")!,
           subtitle: tr(
               "Only moderators and administrators of the group can create posts on it"),
         ),
       ];
 
-  Widget _buildAccessRestrictions() => SettingsSection(
+  SettingsSection _buildAccessRestrictions() => SettingsSection(
         title: tr("Access restrictions"),
         tiles: [
           // Group visibility
           MultiChoicesSettingsTile(
-              title: tr("Group visibility"),
+              title: tr("Group visibility")!,
               choices: _visibilityLevels,
-              currentValue: _groupSettings.visibilityLevel,
-              onChanged: (v) {
-                _groupSettings.visibilityLevel = v;
+              currentValue: _groupSettings!.visibilityLevel,
+              onChanged: (dynamic v) {
+                _groupSettings!.visibilityLevel = v;
                 _updateSettings();
               }),
 
           // Group registration level
           MultiChoicesSettingsTile(
-              title: tr("Group registration level"),
+              title: tr("Group registration level")!,
               choices: _registrationLevels,
-              currentValue: _groupSettings.registrationLevel,
-              onChanged: (v) {
-                _groupSettings.registrationLevel = v;
+              currentValue: _groupSettings!.registrationLevel,
+              onChanged: (dynamic v) {
+                _groupSettings!.registrationLevel = v;
                 _updateSettings();
               }),
 
           // Group posts creation levels
           MultiChoicesSettingsTile(
-              title: tr("Posts creation level"),
+              title: tr("Posts creation level")!,
               choices: _postsCreationLevels,
-              currentValue: _groupSettings.postCreationLevel,
-              onChanged: (s) {
-                _groupSettings.postCreationLevel = s;
+              currentValue: _groupSettings!.postCreationLevel,
+              onChanged: (dynamic s) {
+                _groupSettings!.postCreationLevel = s;
                 _updateSettings();
               }),
 
@@ -253,10 +253,10 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
           SettingsTile.switchTile(
             title: tr("Make members list public"),
             onToggle: (s) {
-              _groupSettings.isMembersListPublic = s;
+              _groupSettings!.isMembersListPublic = s;
               _updateSettings();
             },
-            switchValue: _groupSettings.isMembersListPublic,
+            switchValue: _groupSettings!.isMembersListPublic,
             titleMaxLines: 2,
           )
         ],
@@ -266,19 +266,19 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
       get _conversationMinMembershipLevel => [
             MultiChoiceEntry(
               id: GroupMembershipLevel.ADMINISTRATOR,
-              title: tr("Administrators only"),
+              title: tr("Administrators only")!,
               subtitle: tr(
                   "Only the administrators of the group can access the conversation"),
             ),
             MultiChoiceEntry(
               id: GroupMembershipLevel.MODERATOR,
-              title: tr("Moderators and administrators"),
+              title: tr("Moderators and administrators")!,
               subtitle: tr(
                   "Only moderators and administrators of the group can access the conversation"),
             ),
             MultiChoiceEntry(
               id: GroupMembershipLevel.MEMBER,
-              title: tr("All members"),
+              title: tr("All members")!,
               subtitle: tr(
                   "All the members of the group can access the conversation"),
             ),
@@ -286,17 +286,17 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
 
   SettingsSection _buildConversationsArea() => SettingsSection(
         title: tr("Group conversations"),
-        tiles: _groupSettings.conversations
+        tiles: _groupSettings!.conversations!
             .map(
               (e) {
                 SettingsTile tile =
-                    MultiChoicesSettingsTile<GroupMembershipLevel>(
-                  title: e.name,
+                    MultiChoicesSettingsTile<GroupMembershipLevel?>(
+                  title: e.name!,
                   choices: _conversationMinMembershipLevel,
                   currentValue: e.groupMinMembershipLevel,
                   leading: e.hasLogo
                       ? CachedNetworkImage(
-                          imageUrl: e.logoURL,
+                          imageUrl: e.logoURL!,
                           width: 30,
                         )
                       : Icon(Icons.group, size: 30),
@@ -324,13 +324,13 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
     try {
       final name = await askUserString(
         context: context,
-        title: tr("New conversation name"),
-        message: tr("Please give a name to the new conversation"),
+        title: tr("New conversation name")!,
+        message: tr("Please give a name to the new conversation")!,
         defaultValue: "",
-        hint: tr("Name"),
+        hint: tr("Name")!,
         minLength: 1,
         maxLength: ServerConfigurationHelper
-            .config.conversationsPolicy.maxConversationNameLen,
+            .config!.conversationsPolicy.maxConversationNameLen,
       );
 
       if (name == null) return;
@@ -345,27 +345,27 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
       if (visibility == null) return;
 
       await GroupsHelper.createGroupConversation(NewGroupConversation(
-        groupID: _groupSettings.id,
+        groupID: _groupSettings!.id,
         name: name,
         minMembershipLevel: visibility,
       ));
 
-      _key.currentState.refresh();
+      _key.currentState!.refresh();
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to create a conversation!"));
+      snack(context, tr("Failed to create a conversation!")!);
     }
   }
 
   void _changeConversationVisibility(
-      Conversation conv, GroupMembershipLevel newLevel) async {
+      Conversation conv, GroupMembershipLevel? newLevel) async {
     try {
       await GroupsHelper.setConversationVisibility(conv.id, newLevel);
 
-      _key.currentState.refresh();
+      _key.currentState!.refresh();
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to change conversation visibility level!"));
+      snack(context, tr("Failed to change conversation visibility level!")!);
     }
   }
 
@@ -378,21 +378,21 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
 
       await GroupsHelper.deleteConversation(conv.id);
 
-      _key.currentState.refresh();
+      _key.currentState!.refresh();
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to delete conversation!"));
+      snack(context, tr("Failed to delete conversation!")!);
     }
   }
 
-  Widget _buildGroupLogoArea() {
+  SettingsSection _buildGroupLogoArea() {
     return SettingsSection(
       title: tr("Group logo"),
       tiles: [
         // Current logo
         SettingsTile(
           title: tr("Current logo"),
-          leading: GroupIcon(group: _groupSettings),
+          leading: GroupIcon(group: _groupSettings!),
         ),
 
         // Upload a new logo
@@ -421,10 +421,10 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
     try {
       final logo = await pickImage(context);
       if (logo == null) return;
-      await _doUploadLogo(logo.bytes);
+      await _doUploadLogo(logo.bytes as Uint8List?);
     } catch (e, stack) {
       print("Could not upload new logo! $e\n$stack");
-      showSimpleSnack(context, tr("Could not upload new logo!"));
+      showSimpleSnack(context, tr("Could not upload new logo!")!);
     }
   }
 
@@ -435,13 +435,13 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
       await _doUploadLogo(newLogo);
     } catch (e, stack) {
       print("Could not generate new logo! $e\n$stack");
-      showSimpleSnack(context, tr("Could not generate new random logo!"));
+      showSimpleSnack(context, tr("Could not generate new random logo!")!);
     }
   }
 
-  Future<void> _doUploadLogo(Uint8List bytes) async {
-    await GroupsHelper.uploadNewLogo(_groupSettings.id, bytes);
-    _key.currentState.refresh();
+  Future<void> _doUploadLogo(Uint8List? bytes) async {
+    await GroupsHelper.uploadNewLogo(_groupSettings!.id, bytes);
+    _key.currentState!.refresh();
   }
 
   /// Delete previous group logo
@@ -452,15 +452,15 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
           message: tr("Do you really want to delete the logo of this group ?")))
         return;
 
-      await GroupsHelper.deleteLogo(_groupSettings.id);
-      _key.currentState.refresh();
+      await GroupsHelper.deleteLogo(_groupSettings!.id);
+      _key.currentState!.refresh();
     } catch (e, s) {
       print("Could not delete group logo! $e\n$s");
-      showSimpleSnack(context, tr("Could not delete group logo!"));
+      showSimpleSnack(context, tr("Could not delete group logo!")!);
     }
   }
 
-  Widget _buildDangerZone() {
+  SettingsSection _buildDangerZone() {
     return SettingsSection(
       title: tr("Danger zone"),
       tiles: [
@@ -485,12 +485,12 @@ class _GroupSettingsScreenState extends SafeState<GroupSettingsScreen> {
               "Do you really want to delete this group ? All the posts related to it will be permanently deleted!")))
         return;
 
-      await GroupsHelper.deleteGroup(_groupSettings.id, password);
+      await GroupsHelper.deleteGroup(_groupSettings!.id, password);
 
-      MainController.of(context).popPage();
+      MainController.of(context)!.popPage();
     } catch (e, s) {
       print("Could not delete the group! $e\n$s");
-      showSimpleSnack(context, tr("Could not delete the group"));
+      showSimpleSnack(context, tr("Could not delete the group")!);
     }
   }
 }

lib/ui/screens/groups_list_screen.dart

@@ -19,7 +19,7 @@ class GroupsListScreen extends StatefulWidget {
 }
 
 class _GroupsListScreenState extends SafeState<GroupsListScreen> {
-  GroupsList _groups;
+  GroupsList? _groups;
   bool _error = false;
 
   final _refreshIndicatorKey = GlobalKey<RefreshIndicatorState>();
@@ -41,7 +41,7 @@ class _GroupsListScreenState extends SafeState<GroupsListScreen> {
           hide: !_error,
           actions: [
             MaterialButton(
-              child: Text(tr("Try again").toUpperCase()),
+              child: Text(tr("Try again")!.toUpperCase()),
               onPressed: () => _refreshList(),
             ),
           ],
@@ -61,19 +61,19 @@ class _GroupsListScreenState extends SafeState<GroupsListScreen> {
   }
 
   Widget _buildGroupsList() => ListView(
-        children: (_groups.values.toList()
+        children: (_groups!.values.toList()
               ..sort((one, two) => two.id.compareTo(one.id)))
             .map((g) => ListTile(
                   leading: GroupIcon(group: g),
                   title: Text(g.displayName),
                   subtitle: GroupMembershipWidget(
                     group: g,
-                    onUpdated: () => _refreshIndicatorKey.currentState.show(),
+                    onUpdated: () => _refreshIndicatorKey.currentState!.show(),
                   ),
                   trailing: IconButton(
                       icon: Icon(Icons.delete),
                       onPressed: () => _deleteGroup(g)),
-                  onTap: () => MainController.of(context).openGroup(g.id),
+                  onTap: () => MainController.of(context)!.openGroup(g.id),
                 ))
             .toList(),
       );
@@ -116,10 +116,10 @@ class _GroupsListScreenState extends SafeState<GroupsListScreen> {
 
     if (!await GroupsHelper().removeMembership(g.id))
       showSimpleSnack(
-          context, tr("Could not remove your membership to this group!"));
+          context, tr("Could not remove your membership to this group!")!);
 
     // Refresh the list of groups
-    _refreshIndicatorKey.currentState.show();
+    _refreshIndicatorKey.currentState!.show();
   }
 
   /// Add a group
@@ -127,10 +127,10 @@ class _GroupsListScreenState extends SafeState<GroupsListScreen> {
     try {
       final name = await askUserString(
         context: context,
-        title: tr("Group name"),
-        message: tr("Name of the group to create"),
+        title: tr("Group name")!,
+        message: tr("Name of the group to create")!,
         defaultValue: "",
-        hint: tr("Name of the group"),
+        hint: tr("Name of the group")!,
         maxLength: 50,
       );
 
@@ -138,10 +138,10 @@ class _GroupsListScreenState extends SafeState<GroupsListScreen> {
 
       final groupID = await GroupsHelper.create(name);
 
-      MainController.of(context).openGroup(groupID);
+      MainController.of(context)!.openGroup(groupID);
     } catch (e, s) {
       print("Could not create a new group! $e\n$s");
-      showSimpleSnack(context, tr("Could not create a new group!"));
+      showSimpleSnack(context, tr("Could not create a new group!")!);
     }
   }
 }

lib/ui/screens/notifications_screen.dart

@@ -28,7 +28,7 @@ class NotificationsScreen extends StatefulWidget {
   final bool useSmallDeleteButton;
 
   const NotificationsScreen({
-    Key key,
+    Key? key,
     this.useSmallDeleteButton = false,
   })  : assert(useSmallDeleteButton != null),
         super(key: key);
@@ -38,9 +38,9 @@ class NotificationsScreen extends StatefulWidget {
 }
 
 class _NotificationsScreenState extends SafeState<NotificationsScreen> {
-  NotificationsList _list;
-  UsersList _users;
-  GroupsList _groups;
+  NotificationsList? _list;
+  late UsersList _users;
+  late GroupsList _groups;
   _Status _status = _Status.LOADING;
 
   final _refreshKey = GlobalKey<RefreshIndicatorState>();
@@ -64,12 +64,12 @@ class _NotificationsScreenState extends SafeState<NotificationsScreen> {
       });
 
       setStatus(_Status.NONE);
-    } on Exception catch (e) {
+    } on Exception catch (e, s) {
       print("Exception while getting the list of notifications!");
-      print(e);
-    } on Error catch (e) {
+      print("$e, $s");
+    } on Error catch (e, s) {
       print("Error while getting the list of notifications!");
-      print(e.stackTrace);
+      print("$e, $s");
     }
   }
 
@@ -77,7 +77,7 @@ class _NotificationsScreenState extends SafeState<NotificationsScreen> {
   void initState() {
     super.initState();
 
-    this.listen<NewNumberNotifsEvent>((d) => _refreshKey.currentState.show());
+    this.listen<NewNumberNotifsEvent>((d) => _refreshKey.currentState!.show());
   }
 
   @override
@@ -121,14 +121,14 @@ class _NotificationsScreenState extends SafeState<NotificationsScreen> {
 
   /// Build body
   Widget _buildBody() {
-    if (_status == _Status.ERROR || _list.length == 0)
+    if (_status == _Status.ERROR || _list!.length == 0)
       return SingleChildScrollView(
         physics: AlwaysScrollableScrollPhysics(),
         child: _buildSingleChildCases(),
       );
 
     return ListView(
-      children: _list
+      children: _list!
           .map((f) => _NotificationTile(
                 notification: f,
                 usersList: _users,
@@ -146,16 +146,16 @@ class _NotificationsScreenState extends SafeState<NotificationsScreen> {
           actions: [
             MaterialButton(
               onPressed: () => _loadList(),
-              child: Text(tr("Try again".toUpperCase())),
+              child: Text(tr("Try again".toUpperCase())!),
             )
           ]);
 
     // When there is no notification
-    if (_list.length == 0)
+    if (_list!.length == 0)
       return Padding(
         padding: const EdgeInsets.all(8.0),
         child: Center(
-          child: Text(tr("You do not have any notification now.")),
+          child: Text(tr("You do not have any notification now.")!),
         ),
       );
 
@@ -165,7 +165,7 @@ class _NotificationsScreenState extends SafeState<NotificationsScreen> {
   /// Delete a notification
   void _deleteNotification(n.Notification notif) async {
     setState(() {
-      _list.remove(notif);
+      _list!.remove(notif);
     });
 
     NotificationsHelper().markSeen(notif);
@@ -179,11 +179,11 @@ class _NotificationsScreenState extends SafeState<NotificationsScreen> {
       return;
 
     if (!await NotificationsHelper().deleteAllNotifications()) {
-      showSimpleSnack(context, tr("Could not delete all your notifications!"));
+      showSimpleSnack(context, tr("Could not delete all your notifications!")!);
       return;
     }
 
-    _refreshKey.currentState.show();
+    _refreshKey.currentState!.show();
   }
 }
 
@@ -194,11 +194,11 @@ class _NotificationTile extends StatelessWidget {
   final void Function(n.Notification) onDelete;
 
   const _NotificationTile({
-    Key key,
-    @required this.notification,
-    @required this.usersList,
-    @required this.groupsList,
-    @required this.onDelete,
+    Key? key,
+    required this.notification,
+    required this.usersList,
+    required this.groupsList,
+    required this.onDelete,
   })  : assert(notification != null),
         assert(usersList != null),
         assert(groupsList != null),
@@ -214,51 +214,51 @@ class _NotificationTile extends StatelessWidget {
     switch (notification.type) {
       // Comment
       case n.NotificationType.COMMENT_CREATED:
-        message += tr("posted a comment");
+        message += tr("posted a comment")!;
         break;
 
       // Friendship requests
       case n.NotificationType.SENT_FRIEND_REQUEST:
-        message += tr("sent you a friendship request.");
+        message += tr("sent you a friendship request.")!;
         break;
 
       case n.NotificationType.ACCEPTED_FRIEND_REQUEST:
-        message += tr("accepted your friendship request.");
+        message += tr("accepted your friendship request.")!;
         break;
 
       case n.NotificationType.REJECTED_FRIEND_REQUEST:
-        message += tr("rejected your friendship request.");
+        message += tr("rejected your friendship request.")!;
         break;
 
       // Groups membership
       case n.NotificationType.SENT_GROUP_MEMBERSHIP_INVITATION:
-        message += tr("invited you to join the group");
+        message += tr("invited you to join the group")!;
         break;
 
       case n.NotificationType.ACCEPTED_GROUP_MEMBERSHIP_INVITATION:
-        message += tr("accepted his invitation to join the group");
+        message += tr("accepted his invitation to join the group")!;
         break;
 
       case n.NotificationType.REJECTED_GROUP_MEMBERSHIP_INVITATION:
-        message += tr("rejected his invitation to join the group");
+        message += tr("rejected his invitation to join the group")!;
         break;
 
       case n.NotificationType.SENT_GROUP_MEMBERSHIP_REQUEST:
-        message += tr("sent a request to join the group");
+        message += tr("sent a request to join the group")!;
         break;
 
       case n.NotificationType.ACCEPTED_GROUP_MEMBERSHIP_REQUEST:
-        message += tr("accepted you request to join the group");
+        message += tr("accepted you request to join the group")!;
         break;
 
       case n.NotificationType.REJECTED_GROUP_MEMBERSHIP_REQUEST:
-        message += tr("rejected your request to join the group");
+        message += tr("rejected your request to join the group")!;
         break;
 
       // Generic element creation
       case n.NotificationType.ELEM_CREATED:
         if (notification.onElemType == n.NotificationElementType.POST)
-          message += tr("created a new post");
+          message += tr("created a new post")!;
         break;
 
       case n.NotificationType.ELEM_UPDATED:
@@ -274,24 +274,24 @@ class _NotificationTile extends StatelessWidget {
     // User page
     if (notification.fromContainerType == n.NotificationElementType.USER_PAGE) {
       if (notification.fromUser == notification.fromContainerId)
-        message += tr("on his / her page");
+        message += tr("on his / her page")!;
       else
         message += tr("on %user_name%'s page", args: {
           "user_name": usersList.getUser(notification.fromContainerId).fullName
-        });
+        })!;
     }
 
     // Group page
     if (notification.fromContainerType ==
         n.NotificationElementType.GROUP_PAGE) {
       message += tr("on the group %group%.", args: {
-        "group": groupsList[notification.fromContainerId].displayName
-      });
+        "group": groupsList[notification.fromContainerId]!.displayName
+      })!;
     }
 
     // Group membership
     if (notification.onElemType == n.NotificationElementType.GROUP_MEMBERSHIP)
-      message += groupsList[notification.onElemId].displayName;
+      message += groupsList[notification.onElemId]!.displayName;
 
     return CustomListTile(
       leading: AccountImageWidget(
@@ -299,11 +299,11 @@ class _NotificationTile extends StatelessWidget {
       ),
       onTap: () => _onTap(context),
       title: Text(message),
-      subtitle: Text(diffTimeFromNowToStr(notification.timeCreate)),
+      subtitle: Text(diffTimeFromNowToStr(notification.timeCreate)!),
       onLongPressOpenMenu: (position) {
         showMenu(context: context, position: position, items: [
           PopupMenuItem(
-            child: Text(tr("Delete")),
+            child: Text(tr("Delete")!),
             value: _PopupMenuActions.DELETE,
           ),
         ]).then(_popupMenuAction);
@@ -311,7 +311,7 @@ class _NotificationTile extends StatelessWidget {
     );
   }
 
-  void _popupMenuAction(_PopupMenuActions value) {
+  void _popupMenuAction(_PopupMenuActions? value) {
     switch (value) {
       case _PopupMenuActions.DELETE:
         onDelete(notification);
@@ -327,10 +327,10 @@ class _NotificationTile extends StatelessWidget {
       openUserPage(userID: notification.fromUser, context: context);
     } else if (notification.onElemType ==
         n.NotificationElementType.GROUP_MEMBERSHIP) {
-      MainController.of(context).openGroup(notification.onElemId);
+      MainController.of(context)!.openGroup(notification.onElemId);
     } else {
       showSimpleSnack(context,
-          tr("This kind of notification is not supported yet by this application."));
+          tr("This kind of notification is not supported yet by this application.")!);
       return;
     }
 

lib/ui/screens/other_friends_lists_screen.dart

@@ -16,8 +16,8 @@ class OtherUserFriendsListScreen extends StatefulWidget {
   final bool enableAppBar;
 
   const OtherUserFriendsListScreen({
-    Key key,
-    @required this.userID,
+    Key? key,
+    required this.userID,
     this.enableAppBar = true,
   })  : assert(userID != null),
         assert(enableAppBar != null),
@@ -33,12 +33,12 @@ class _OtherUserFriendsListScreenState
   final FriendsHelper friendsHelper = FriendsHelper();
   final UsersHelper usersHelper = UsersHelper();
 
-  Set<int> _friendsList;
-  UsersList _usersInfo;
+  late Set<int> _friendsList;
+  UsersList? _usersInfo;
   bool _error = false;
 
-  String get _routeName => tr("Friends of %name%",
-      args: {"name": _usersInfo.getUser(widget.userID).displayName});
+  String? get _routeName => tr("Friends of %name%",
+      args: {"name": _usersInfo!.getUser(widget.userID).displayName});
 
   void setError(bool e) => setState(() => _error = e);
 
@@ -79,16 +79,16 @@ class _OtherUserFriendsListScreenState
     return Scaffold(
       appBar: widget.enableAppBar
           ? AppBar(
-              title: Text(_routeName),
+              title: Text(_routeName!),
             )
           : null,
       body: ListView.builder(
         itemCount: _friendsList.length,
         itemBuilder: (c, i) => SimpleUserTile(
-          user: _usersInfo.getUser(_friendsList.elementAt(i)),
+          user: _usersInfo!.getUser(_friendsList.elementAt(i)),
           onTap: (u) => openUserPage(
             context: context,
-            userID: u.id,
+            userID: u.id!,
           ),
         ),
       ),
@@ -104,7 +104,7 @@ class _OtherUserFriendsListScreenState
         actions: [
           TextButton(
             child: Text(
-              tr("Try again").toUpperCase(),
+              tr("Try again")!.toUpperCase(),
               style: TextStyle(color: Colors.white),
             ),
             onPressed: load,

lib/ui/screens/search_screen.dart

@@ -24,9 +24,9 @@ class SearchScreen extends StatefulWidget {
 }
 
 class _SearchScreenState extends State<SearchScreen> {
-  SearchResultsList _searchResultsList;
-  UsersList _usersList;
-  GroupsList _groupsList;
+  SearchResultsList? _searchResultsList;
+  late UsersList _usersList;
+  late GroupsList _groupsList;
 
   @override
   Widget build(BuildContext context) {
@@ -44,13 +44,13 @@ class _SearchScreenState extends State<SearchScreen> {
               ? Container()
               : Expanded(
                   child: ListView(
-                    children: _searchResultsList
+                    children: _searchResultsList!
                         .map((f) => f.kind == SearchResultKind.USER
                             ? _SearchResultUser(
                                 user: _usersList.getUser(f.id),
                               )
                             : _SearchResultGroup(
-                                group: _groupsList[f.id],
+                                group: _groupsList[f.id]!,
                               ))
                         .toList(),
                   ),
@@ -78,7 +78,7 @@ class _SearchScreenState extends State<SearchScreen> {
       print(e);
       print(stack);
 
-      showSimpleSnack(context, tr("Could not peform search!"));
+      showSimpleSnack(context, tr("Could not peform search!")!);
     }
   }
 }
@@ -86,7 +86,7 @@ class _SearchScreenState extends State<SearchScreen> {
 class _SearchResultUser extends StatelessWidget {
   final User user;
 
-  const _SearchResultUser({Key key, this.user})
+  const _SearchResultUser({Key? key, required this.user})
       : assert(user != null),
         super(key: key);
 
@@ -97,7 +97,7 @@ class _SearchResultUser extends StatelessWidget {
         user: user,
       ),
       title: Text(user.displayName),
-      onTap: () => MainController.of(context).openUserPage(user.id),
+      onTap: () => MainController.of(context)!.openUserPage(user.id!),
     );
   }
 }
@@ -105,7 +105,7 @@ class _SearchResultUser extends StatelessWidget {
 class _SearchResultGroup extends StatelessWidget {
   final Group group;
 
-  const _SearchResultGroup({Key key, this.group})
+  const _SearchResultGroup({Key? key, required this.group})
       : assert(group != null),
         super(key: key);
 
@@ -114,8 +114,8 @@ class _SearchResultGroup extends StatelessWidget {
     return ListTile(
       leading: GroupIcon(group: group),
       title: Text(group.displayName),
-      subtitle: Text(tr("Group")),
-      onTap: () => MainController.of(context).openGroup(group.id),
+      subtitle: Text(tr("Group")!),
+      onTap: () => MainController.of(context)!.openGroup(group.id),
     );
   }
 }

lib/ui/screens/unread_conversations_screen.dart

@@ -5,6 +5,7 @@ import 'package:comunic/helpers/users_helper.dart';
 import 'package:comunic/lists/groups_list.dart';
 import 'package:comunic/lists/unread_conversations_list.dart';
 import 'package:comunic/lists/users_list.dart';
+import 'package:comunic/models/unread_conversation.dart';
 import 'package:comunic/ui/routes/main_route/main_route.dart';
 import 'package:comunic/ui/widgets/async_screen_widget.dart';
 import 'package:comunic/ui/widgets/conversation_image_widget.dart';
@@ -25,9 +26,9 @@ class UnreadConversationsScreen extends StatefulWidget {
 
 class _UnreadConversationsScreenState
     extends SafeState<UnreadConversationsScreen> {
-  UnreadConversationsList _list;
-  UsersList _users;
-  GroupsList _groups;
+  late UnreadConversationsList _list;
+  UsersList? _users;
+  GroupsList? _groups;
 
   final _key = GlobalKey<AsyncScreenWidgetState>();
 
@@ -41,7 +42,7 @@ class _UnreadConversationsScreenState
   void initState() {
     super.initState();
 
-    listen<NewNumberUnreadConversations>((e) => _key.currentState.refresh());
+    listen<NewNumberUnreadConversations>((e) => _key.currentState!.refresh());
   }
 
   @override
@@ -50,7 +51,7 @@ class _UnreadConversationsScreenState
       key: _key,
       onReload: _refresh,
       onBuild: _buildList,
-      errorMessage: tr("Could not load the list of unread conversations!"),
+      errorMessage: tr("Could not load the list of unread conversations!")!,
     );
   }
 
@@ -61,7 +62,7 @@ class _UnreadConversationsScreenState
         child: Padding(
           padding: const EdgeInsets.all(8.0),
           child: Text(
-            tr("You do not have any unread conversation yet..."),
+            tr("You do not have any unread conversation yet...")!,
             textAlign: TextAlign.center,
           ),
         ),
@@ -74,34 +75,34 @@ class _UnreadConversationsScreenState
   }
 
   Widget _tileBuilder(BuildContext context, int index) {
-    final conv = _list[index];
+    final UnreadConversation conv = _list[index];
 
     final message = _list[index].message;
 
-    final singleUserConv = conv.conv.members.length < 3;
+    final singleUserConv = conv.conv.members!.length < 3;
 
-    String messageStr;
+    String? messageStr;
     if (message.hasFile)
       messageStr = tr("New file");
     else if (message.hasMessage)
       messageStr = singleUserConv
           ? message.message.content
           : tr("%1% : %2%", args: {
-              "1": _users.getUser(message.userID).fullName,
+              "1": _users!.getUser(message.userID).fullName,
               "2": message.message.content,
             });
     else
-      message.serverMessage.getText(_users);
+      message.serverMessage!.getText(_users);
 
     return ListTile(
       leading: ConversationImageWidget(
         conversation: conv.conv,
-        users: _users,
+        users: _users!,
         group: conv.conv.isGroupConversation
-            ? _groups.getGroup(conv.conv.groupID)
+            ? _groups!.getGroup(conv.conv.groupID)
             : null,
       ),
-      title: Text(ConversationsHelper.getConversationName(conv.conv, _users)),
+      title: Text(ConversationsHelper.getConversationName(conv.conv, _users)!),
       subtitle: RichText(
         text: TextSpan(style: Theme.of(context).textTheme.bodyText2, children: [
           TextSpan(
@@ -110,9 +111,9 @@ class _UnreadConversationsScreenState
           ),
         ]),
       ),
-      trailing: Text(diffTimeFromNowToStr(conv.message.timeSent)),
+      trailing: Text(diffTimeFromNowToStr(conv.message.timeSent!)!),
       onTap: () =>
-          MainController.of(context).openConversationById(conv.conv.id),
+          MainController.of(context)!.openConversationById(conv.conv.id!),
     );
   }
 }

lib/ui/screens/update_conversation_screen.dart

@@ -32,7 +32,7 @@ class UpdateConversationScreen extends StatefulWidget {
   final convID;
 
   const UpdateConversationScreen({
-    Key key,
+    Key? key,
     this.convID,
   }) : super(key: key);
 
@@ -41,19 +41,19 @@ class UpdateConversationScreen extends StatefulWidget {
 }
 
 class _UpdateConversationScreen extends State<UpdateConversationScreen> {
-  Conversation _conversation;
+  late Conversation _conversation;
 
   TextEditingController _nameController = TextEditingController();
   TextEditingController _colorController = TextEditingController();
   UsersList _members = UsersList();
-  Set<int> _admins = Set();
+  Set<int?> _admins = Set();
   bool _followConversation = true;
-  bool _canEveryoneAddMembers = true;
-  String _image;
+  bool? _canEveryoneAddMembers = true;
+  String? _image;
 
   String get _conversationColor => _colorController.text;
 
-  Color get _color {
+  Color? get _color {
     if (_conversationColor == null || _conversationColor.isEmpty) return null;
 
     try {
@@ -72,7 +72,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
       isUpdating && _conversation.isGroupConversation;
 
   bool get _canAddMembers =>
-      (isAdmin || _conversation.canEveryoneAddMembers) &&
+      (isAdmin || _conversation.canEveryoneAddMembers!) &&
       (!isUpdating || !_conversation.isManaged);
 
   get _isValid => _members.length > 0;
@@ -104,8 +104,8 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
         appBar: AppBar(
           leading: ComunicBackButton(),
           title: Text(isUpdating
-              ? tr("Update conversation")
-              : tr("Create a conversation")),
+              ? tr("Update conversation")!
+              : tr("Create a conversation")!),
           actions: [
             IconButton(
                 icon: Icon(Icons.check),
@@ -115,7 +115,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
         body: AsyncScreenWidget(
           onReload: _init,
           onBuild: _buildBody,
-          errorMessage: tr("Failed to load conversation settings!"),
+          errorMessage: tr("Failed to load conversation settings!")!,
         ),
       );
 
@@ -126,7 +126,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
         child: Column(
           children: <Widget>[
             _isGroupConversation
-                ? Text(tr("This conversation is managed by a group"))
+                ? Text(tr("This conversation is managed by a group")!)
                 : Container(),
 
             // Conversation name
@@ -163,7 +163,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
                     _followConversation = b;
                   }),
                 ),
-                Text(tr("Follow conversation"))
+                Text(tr("Follow conversation")!)
               ],
             ),
 
@@ -173,7 +173,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
                 : Row(
                     children: <Widget>[
                       Switch.adaptive(
-                        value: _canEveryoneAddMembers,
+                        value: _canEveryoneAddMembers!,
                         onChanged: isAdmin
                             ? (b) => setState(() {
                                   _canEveryoneAddMembers = b;
@@ -182,7 +182,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
                       ),
                       Flexible(
                           child: Text(tr(
-                              "Allow all members of the conversation to add users")))
+                              "Allow all members of the conversation to add users")!))
                     ],
                   ),
 
@@ -190,7 +190,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
             PickUserWidget(
                 resetOnChoose: true,
                 keepFocusOnChoose: true,
-                label: tr("Add member"),
+                label: tr("Add member")!,
                 enabled: _canAddMembers,
                 onSelectUser: (user) => _addMember(user)),
 
@@ -215,12 +215,12 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
                 onSelected: (choice) => _membersMenuItemSelected(user, choice),
                 itemBuilder: (c) => <PopupMenuEntry<_MembersMenuChoices>>[
                   PopupMenuItem(
-                    child: Text(tr("Toggle admin status")),
+                    child: Text(tr("Toggle admin status")!),
                     value: _MembersMenuChoices.TOGGLE_ADMIN_STATUS,
                     enabled: isUpdating && isAdmin && user.id != userID(),
                   ),
                   PopupMenuItem(
-                    child: Text(tr("Remove")),
+                    child: Text(tr("Remove")!),
                     value: _MembersMenuChoices.REMOVE,
                     enabled: isAdmin && user.id != userID(),
                   ),
@@ -260,7 +260,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
       setState(() => _members.insert(0, user));
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to add member to conversation!"));
+      snack(context, tr("Failed to add member to conversation!")!);
     }
   }
 
@@ -275,14 +275,14 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
       });
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to remove member!"));
+      snack(context, tr("Failed to remove member!")!);
     }
   }
 
   void _toggleAdminStatus(User user) async {
     try {
       final setAdmin = !_admins.contains(user.id);
-      await ConversationsHelper.setAdmin(_conversation.id, user.id, setAdmin);
+      await ConversationsHelper.setAdmin(_conversation.id!, user.id!, setAdmin);
 
       setState(() {
         if (!setAdmin)
@@ -292,7 +292,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
       });
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to toggle admin status of user!"));
+      snack(context, tr("Failed to toggle admin status of user!")!);
     }
   }
 
@@ -306,17 +306,17 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
                 name: _nameController.text,
                 members: _members.map((element) => element.id).toList(),
                 follow: _followConversation,
-                canEveryoneAddMembers: _canEveryoneAddMembers,
-                color: _color));
+                canEveryoneAddMembers: _canEveryoneAddMembers!,
+                color: _color)) ;
 
-        MainController.of(context).popPage();
-        MainController.of(context).openConversationById(conversationID);
+        MainController.of(context)!.popPage();
+        MainController.of(context)!.openConversationById(conversationID);
         return;
       }
 
       // Update conversation settings
       final newSettings = NewConversationsSettings(
-        convID: _conversation.id,
+        convID: _conversation.id!,
         following: _followConversation,
         isComplete: isAdmin,
         name: _nameController.text,
@@ -326,10 +326,10 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
 
       await ConversationsHelper.updateConversation(newSettings);
 
-      MainController.of(context).popPage();
+      MainController.of(context)!.popPage();
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to update conversation settings!"));
+      snack(context, tr("Failed to update conversation settings!")!);
     }
   }
 
@@ -337,12 +337,12 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
   Widget _buildConversationImageWidget() => Column(
         children: [
           SizedBox(height: 10),
-          Text(tr("Conversation logo"),
+          Text(tr("Conversation logo")!,
               style: TextStyle(fontWeight: FontWeight.bold)),
           SizedBox(height: 5),
           _image == null
               ? Text("No logo defined yet.")
-              : CachedNetworkImage(imageUrl: _image),
+              : CachedNetworkImage(imageUrl: _image!),
           SizedBox(height: 5),
           isAdmin
               ? Row(
@@ -350,14 +350,14 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
                   children: [
                     OutlinedButton(
                       onPressed: _uploadNewLogo,
-                      child: Text(tr("Change logo")),
+                      child: Text(tr("Change logo")!),
                     ),
                     SizedBox(width: 5),
                     _image == null
                         ? Container()
                         : ElevatedButton(
                             onPressed: _deleteLogo,
-                            child: Text(tr("Delete logo")),
+                            child: Text(tr("Delete logo")!),
                             style: ButtonStyle(
                                 backgroundColor:
                                     MaterialStateProperty.all(Colors.red)),
@@ -375,8 +375,8 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
       final newLogo = await showPickFileDialog(
         context: context,
         allowedMimeTypes: ["image/png", "image/jpeg", "image/gif"],
-        imageMaxWidth: srvConfig.conversationsPolicy.maxLogoWidth,
-        imageMaxHeight: srvConfig.conversationsPolicy.maxLogoHeight,
+        imageMaxWidth: srvConfig!.conversationsPolicy.maxLogoWidth,
+        imageMaxHeight: srvConfig!.conversationsPolicy.maxLogoHeight,
       );
 
       if (newLogo == null) return;
@@ -388,7 +388,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
       setState(() => _image = newConvSettings.logoURL);
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to change conversation logo !"));
+      snack(context, tr("Failed to change conversation logo !")!);
     }
   }
 
@@ -404,7 +404,7 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
       setState(() => _image = null);
     } catch (e, s) {
       logError(e, s);
-      snack(context, tr("Failed to remove conversation logo!"));
+      snack(context, tr("Failed to remove conversation logo!")!);
     }
   }
 }

lib/ui/screens/user_access_denied_screen.dart

@@ -17,7 +17,7 @@ import 'package:flutter/material.dart';
 class UserAccessDeniedScreen extends StatefulWidget {
   final int userID;
 
-  const UserAccessDeniedScreen({Key key, @required this.userID})
+  const UserAccessDeniedScreen({Key? key, required this.userID})
       : assert(userID != null),
         super(key: key);
 
@@ -31,8 +31,8 @@ class _UserAccessDeniedScreenState extends SafeState<UserAccessDeniedScreen> {
 
   final _key = GlobalKey<AsyncScreenWidgetState>();
 
-  FriendStatus _status;
-  User _user;
+  late FriendStatus _status;
+  late User _user;
 
   Future<void> refresh() async {
     final status = await friendsHelper.getFriendshipStatus(widget.userID);
@@ -40,7 +40,7 @@ class _UserAccessDeniedScreenState extends SafeState<UserAccessDeniedScreen> {
 
     // Check if the two users are friend now
     if (status.areFriend) {
-      final controller = MainController.of(context);
+      final controller = MainController.of(context)!;
       controller.popPage();
       controller.openUserPage(widget.userID);
     }
@@ -55,7 +55,7 @@ class _UserAccessDeniedScreenState extends SafeState<UserAccessDeniedScreen> {
         key: _key,
         onReload: refresh,
         onBuild: _buildPage,
-        errorMessage: tr("Could not load friendship information!"));
+        errorMessage: tr("Could not load friendship information!")!);
   }
 
   Widget _buildPage() {
@@ -77,10 +77,10 @@ class _UserAccessDeniedScreenState extends SafeState<UserAccessDeniedScreen> {
                 _user.displayName,
                 style: TextStyle(fontSize: 25.0),
               ),
-              Text(tr("This account is private.")),
+              Text(tr("This account is private.")!),
               FriendshipStatusWidget(
                 status: _status,
-                onFriendshipUpdated: () => _key.currentState.refresh(),
+                onFriendshipUpdated: () => _key.currentState!.refresh(),
               )
             ],
           ),

lib/ui/screens/user_page_screen.dart

@@ -20,7 +20,7 @@ enum _PageStatus { LOADING, ERROR, READY }
 class UserPageScreen extends StatefulWidget {
   final int userID;
 
-  const UserPageScreen({Key key, @required this.userID})
+  const UserPageScreen({Key? key, required this.userID})
       : assert(userID != null),
         super(key: key);
 
@@ -34,8 +34,8 @@ class _UserPageScreenState extends SafeState<UserPageScreen> {
 
   // Objects members
   _PageStatus _status = _PageStatus.LOADING;
-  AdvancedUserInfo _userInfo;
-  FriendStatus _frienshipStatus;
+  late AdvancedUserInfo _userInfo;
+  FriendStatus? _frienshipStatus;
   final _refreshIndicatorKey = GlobalKey<RefreshIndicatorState>();
 
   _setStatus(_PageStatus s) => setState(() => _status = s);
@@ -65,7 +65,7 @@ class _UserPageScreenState extends SafeState<UserPageScreen> {
       _setStatus(_PageStatus.ERROR);
 
       if (e.cause == GetUserAdvancedInformationErrorCause.NOT_AUTHORIZED) {
-        final controller = MainController.of(context);
+        final controller = MainController.of(context)!;
         controller.popPage();
         controller.openUserAccessDeniedPage(widget.userID);
       }
@@ -94,7 +94,7 @@ class _UserPageScreenState extends SafeState<UserPageScreen> {
   Widget _buildError() {
     return Scaffold(
       appBar: AppBar(
-        title: Text(tr("Error")),
+        title: Text(tr("Error")!),
       ),
       body: Center(
           child:
@@ -102,7 +102,7 @@ class _UserPageScreenState extends SafeState<UserPageScreen> {
         TextButton(
           onPressed: _getUserInfo,
           child: Text(
-            tr("Retry").toUpperCase(),
+            tr("Retry")!.toUpperCase(),
             style: TextStyle(color: Colors.white),
           ),
         )
@@ -114,12 +114,12 @@ class _UserPageScreenState extends SafeState<UserPageScreen> {
     return isTablet(context)
         ? UserPageTablet(
             userInfo: _userInfo,
-            onNeedRefresh: () => _refreshIndicatorKey.currentState.show(),
+            onNeedRefresh: () => _refreshIndicatorKey.currentState!.show(),
             friendshipStatus: _frienshipStatus,
           )
         : UserMobilePage(
             userInfo: _userInfo,
-            onNeedRefresh: () => _refreshIndicatorKey.currentState.show(),
+            onNeedRefresh: () => _refreshIndicatorKey.currentState!.show(),
           );
   }
 }

lib/ui/screens/user_page_sections/about_user_section.dart

@@ -19,8 +19,8 @@ class AboutUserSection extends StatefulWidget {
   final AdvancedUserInfo user;
 
   const AboutUserSection({
-    Key key,
-    @required this.user,
+    Key? key,
+    required this.user,
   })  : assert(user != null),
         super(key: key);
 
@@ -29,7 +29,7 @@ class AboutUserSection extends StatefulWidget {
 }
 
 class _AboutUserSectionState extends State<AboutUserSection> {
-  FriendStatus _friendStatus;
+  late FriendStatus _friendStatus;
 
   final _screenKey = GlobalKey<AsyncScreenWidgetState>();
 
@@ -38,14 +38,14 @@ class _AboutUserSectionState extends State<AboutUserSection> {
       _friendStatus = await FriendsHelper().getFriendshipStatus(widget.user.id);
   }
 
-  void _toggleRefresh() => _screenKey.currentState.refresh();
+  void _toggleRefresh() => _screenKey.currentState!.refresh();
 
   @override
   Widget build(BuildContext context) => AsyncScreenWidget(
       key: _screenKey,
       onReload: _init,
       onBuild: _buildList,
-      errorMessage: tr("Failed to load user information!"));
+      errorMessage: tr("Failed to load user information!")!);
 
   Widget _buildList() => ListView(
         children: [
@@ -58,7 +58,7 @@ class _AboutUserSectionState extends State<AboutUserSection> {
           widget.user.hasPersonalWebsite
               ? ListTile(
                   leading: Icon(Icons.link),
-                  title: Text(tr("Personal Website")),
+                  title: Text(tr("Personal Website")!),
                   subtitle: Text(widget.user.personalWebsite),
                   onTap: () => launch(widget.user.personalWebsite),
                 )
@@ -68,7 +68,7 @@ class _AboutUserSectionState extends State<AboutUserSection> {
           widget.user.hasPublicNote
               ? ListTile(
                   leading: Icon(Icons.note),
-                  title: Text(tr("Note")),
+                  title: Text(tr("Note")!),
                   subtitle: TextWidget(
                       content: DisplayedString(widget.user.publicNote)),
                 )
@@ -78,7 +78,7 @@ class _AboutUserSectionState extends State<AboutUserSection> {
           widget.user.hasVirtualDirectory
               ? ListTile(
                   leading: Icon(Icons.alternate_email),
-                  title: Text(tr("Virtual directory")),
+                  title: Text(tr("Virtual directory")!),
                   subtitle: Text("@${widget.user.virtualDirectory}"))
               : Container(),
 
@@ -87,10 +87,10 @@ class _AboutUserSectionState extends State<AboutUserSection> {
               ? Container()
               : ListTile(
                   leading: Icon(Icons.email_outlined),
-                  title: Text(tr("Email address")),
-                  subtitle: Text(widget.user.emailAddress),
+                  title: Text(tr("Email address")!),
+                  subtitle: Text(widget.user.emailAddress!),
                   onTap: () =>
-                      copyToClipboard(context, widget.user.emailAddress),
+                      copyToClipboard(context, widget.user.emailAddress!),
                 ),
 
           // User location
@@ -98,16 +98,16 @@ class _AboutUserSectionState extends State<AboutUserSection> {
               ? Container()
               : ListTile(
                   leading: Icon(Icons.location_on),
-                  title: Text(tr("Location")),
-                  subtitle: Text(widget.user.location),
-                  onTap: () => copyToClipboard(context, widget.user.location),
+                  title: Text(tr("Location")!),
+                  subtitle: Text(widget.user.location!),
+                  onTap: () => copyToClipboard(context, widget.user.location!),
                 ),
 
           // Number of friends
           widget.user.isFriendsListPublic
               ? ListTile(
                   leading: Icon(Icons.group),
-                  title: Text(tr("Number of friends")),
+                  title: Text(tr("Number of friends")!),
                   subtitle: Text(widget.user.numberFriends.toString()),
                 )
               : Container(),
@@ -115,20 +115,20 @@ class _AboutUserSectionState extends State<AboutUserSection> {
           // Member for
           ListTile(
             leading: Icon(Icons.access_time_rounded),
-            title: Text(tr("Member for")),
+            title: Text(tr("Member for")!),
             subtitle:
-                Text(diffTimeFromNowToStr(widget.user.accountCreationTime)),
+                Text(diffTimeFromNowToStr(widget.user.accountCreationTime)!),
           ),
 
           // Account visibility
           ListTile(
             leading: Icon(Icons.remove_red_eye),
-            title: Text(tr("Account visibility")),
+            title: Text(tr("Account visibility")!),
             subtitle: Text(widget.user.pageVisibility == UserPageVisibility.OPEN
-                ? tr("Open page")
+                ? tr("Open page")!
                 : (widget.user.pageVisibility == UserPageVisibility.PUBLIC
-                    ? tr("Public page")
-                    : tr("Private page"))),
+                    ? tr("Public page")!
+                    : tr("Private page")!)),
           ),
         ],
       );

lib/ui/screens/user_page_sections/user_page_header.dart

@@ -14,9 +14,9 @@ class UserPageHeader extends StatelessWidget {
   final Color bgColor;
 
   const UserPageHeader({
-    Key key,
-    @required this.user,
-    @required this.bgColor,
+    Key? key,
+    required this.user,
+    required this.bgColor,
   })  : assert(user != null),
         super(key: key);
 

lib/ui/screens/user_page_sections/user_posts_section.dart

@@ -13,8 +13,8 @@ class UserPostsSection extends StatefulWidget {
   final AdvancedUserInfo user;
 
   const UserPostsSection({
-    Key key,
-    @required this.user,
+    Key? key,
+    required this.user,
   })  : assert(user != null),
         super(key: key);
 
@@ -23,7 +23,7 @@ class UserPostsSection extends StatefulWidget {
 }
 
 class _UserPostsSectionState extends State<UserPostsSection> {
-  int get _userID => widget.user.id;
+  int? get _userID => widget.user.id;
 
   final _postsKey = GlobalKey<PostsListWidgetState>();
 
@@ -34,7 +34,7 @@ class _UserPostsSectionState extends State<UserPostsSection> {
           widget.user.canPostTexts
               ? PostCreateFormWidget(
                   postTarget: PostTarget.USER_PAGE,
-                  targetID: _userID,
+                  targetID: _userID!,
                   onCreated: _postCreated,
                 )
               : Container()
@@ -45,6 +45,6 @@ class _UserPostsSectionState extends State<UserPostsSection> {
       );
 
   void _postCreated() {
-    _postsKey.currentState.loadPostsList(getOlder: false);
+    _postsKey.currentState!.loadPostsList(getOlder: false);
   }
 }