Continue to fix deprecation warnings

lib/ui/screens/call_screen.dart

@@ -544,7 +544,7 @@ class _CallScreenState extends SafeState<CallScreen> {
         .where((f) => f.hasVideoStream && _renderers.containsKey(f.userID))
         .toList();
 
-    final rows = List<Row>();
+    final rows = <Row>[];
 
     var numberRows = sqrt(availableVideos.length).ceil();
     var numberCols = numberRows;

lib/ui/screens/conversation_screen.dart

@@ -355,7 +355,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
 
     //Check the result of the operation
     if (result != SendMessageResult.SUCCESS)
-      Scaffold.of(context).showSnackBar(
+      ScaffoldMessenger.of(context).showSnackBar(
         SnackBar(
           content: Text(
             result == SendMessageResult.MESSAGE_REJECTED
@@ -637,7 +637,7 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
             Spacer(flex: 1),
             Text("${(_sendProgress * 100).toInt()}%"),
             Spacer(flex: 1),
-            OutlineButton(
+            OutlinedButton(
               onPressed: () => _sendCancel.cancel(),
               child: Text(tr("Cancel").toUpperCase()),
             ),
@@ -724,13 +724,13 @@ class _ConversationScreenState extends SafeState<ConversationScreen> {
           textAlign: TextAlign.justify,
         ),
         actions: <Widget>[
-          FlatButton(
+          TextButton(
             child: Text(
               tr("Cancel").toUpperCase(),
             ),
             onPressed: () => Navigator.pop(c, false),
           ),
-          FlatButton(
+          TextButton(
             child: Text(
               tr("Confirm").toUpperCase(),
               style: TextStyle(color: Colors.red),

lib/ui/screens/conversations_list_screen.dart

@@ -87,7 +87,7 @@ class _ConversationScreenState extends SafeState<ConversationsListScreen> {
     return buildErrorCard(
       tr("Could not retrieve the list of conversations!"),
       actions: <Widget>[
-        FlatButton(
+        TextButton(
           onPressed: () => _refreshIndicatorKey.currentState.show(),
           child: Text(
             tr("Retry").toUpperCase(),
@@ -138,7 +138,7 @@ class _ConversationScreenState extends SafeState<ConversationsListScreen> {
       await _conversationsHelper.deleteConversation(conversation.id);
     } catch (e, s) {
       print("Failed to leave conversation! $e => $s");
-      Scaffold.of(context).showSnackBar(
+      ScaffoldMessenger.of(context).showSnackBar(
           SnackBar(content: Text(tr("Could not leave the conversation!"))));
     }
 

lib/ui/screens/friends_list_screen.dart

@@ -91,7 +91,7 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
   Widget _buildError() => buildErrorCard(
         tr("Could not load your list of friends!"),
         actions: [
-          FlatButton(
+          TextButton(
             onPressed: _refreshList,
             child: Text(
               tr("Retry").toUpperCase(),
@@ -171,11 +171,11 @@ class _FriendsListScreenState extends SafeState<FriendsListScreen> {
         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!")),
         actions: <Widget>[
-          FlatButton(
+          TextButton(
             onPressed: () => Navigator.pop(context, false),
             child: Text(tr("Cancel").toUpperCase()),
           ),
-          FlatButton(
+          TextButton(
             onPressed: () => Navigator.pop(context, true),
             child: Text(
               tr("Confirm").toUpperCase(),

lib/ui/screens/other_friends_lists_screen.dart

@@ -97,7 +97,7 @@ class _OtherUserFriendsListScreenState
           "Could not get the list of friends of this user !",
         ),
         actions: [
-          FlatButton(
+          TextButton(
             child: Text(
               tr("Try again").toUpperCase(),
               style: TextStyle(color: Colors.white),

lib/ui/screens/update_conversation_screen.dart

@@ -337,17 +337,19 @@ class _UpdateConversationScreen extends State<UpdateConversationScreen> {
               ? Row(
                   mainAxisAlignment: MainAxisAlignment.center,
                   children: [
-                    OutlineButton(
+                    OutlinedButton(
                       onPressed: _uploadNewLogo,
                       child: Text(tr("Change logo")),
                     ),
                     SizedBox(width: 5),
                     _image == null
                         ? Container()
-                        : OutlineButton(
+                        : ElevatedButton(
                             onPressed: _deleteLogo,
                             child: Text(tr("Delete logo")),
-                            highlightedBorderColor: Colors.red,
+                            style: ButtonStyle(
+                                backgroundColor:
+                                    MaterialStateProperty.all(Colors.red)),
                           ),
                   ],
                 )

lib/ui/screens/user_page_screen.dart

@@ -99,7 +99,7 @@ class _UserPageScreenState extends SafeState<UserPageScreen> {
       body: Center(
           child:
               buildErrorCard(tr("Could not get user information!"), actions: [
-        FlatButton(
+        TextButton(
           onPressed: _getUserInfo,
           child: Text(
             tr("Retry").toUpperCase(),