Get older messages

lib/ui/screens/conversation_screen.dart

@@ -6,6 +6,7 @@ import 'package:comunic/lists/conversation_messages_list.dart';
 import 'package:comunic/lists/users_list.dart';
 import 'package:comunic/models/new_conversation_message.dart';
 import 'package:comunic/ui/tiles/conversation_message_tile.dart';
+import 'package:comunic/ui/widgets/scroll_watcher.dart';
 import 'package:comunic/utils/files_utils.dart';
 import 'package:comunic/utils/intl_utils.dart';
 import 'package:comunic/utils/list_utils.dart';
@@ -17,6 +18,7 @@ import 'package:flutter/material.dart';
 /// @author Pierre HUBERT
 
 enum ErrorLevel { NONE, MINOR, MAJOR }
+enum _OlderMessagesLevel { NONE, LOADING, NO_MORE_AVAILABLE }
 
 class ConversationScreen extends StatefulWidget {
   final int conversationID;
@@ -42,6 +44,14 @@ class _ConversationScreenState extends State<ConversationScreen> {
   bool _isSendingMessage = false;
   TextEditingController _textEditingController = TextEditingController();
   Timer _refreshTime;
+  ScrollWatcher _scrollController;
+  _OlderMessagesLevel _loadingOlderMessages = _OlderMessagesLevel.NONE;
+
+  @override
+  void initState() {
+    super.initState();
+    _scrollController = ScrollWatcher(onReachBottom: _loadOlderMessages);
+  }
 
   @override
   void didChangeDependencies() {
@@ -59,6 +69,10 @@ class _ConversationScreenState extends State<ConversationScreen> {
 
   void _setSending(bool sending) => setState(() => _isSendingMessage = sending);
 
+  void _setLoadingOlderMessagesState(_OlderMessagesLevel state) => setState(() {
+        _loadingOlderMessages = state;
+      });
+
   /// Method called when an error occurred while loading messages
   void _errorLoading() {
     _setError(_messages == null ? ErrorLevel.MAJOR : ErrorLevel.MINOR);
@@ -89,6 +103,47 @@ class _ConversationScreenState extends State<ConversationScreen> {
     // anything (we wait for the online request)
     if (messages.length == 0 && !online) return;
 
+    await _applyNewMessages(messages);
+  }
+
+  /// Get older messages
+  Future<void> _loadOlderMessages() async {
+    if (_loadingOlderMessages != _OlderMessagesLevel.NONE ||
+        _messages == null ||
+        _messages.length == 0) return;
+
+    // Let's start to load older messages
+    _setLoadingOlderMessagesState(_OlderMessagesLevel.LOADING);
+
+    final messages = await _conversationsHelper.getOlderMessages(
+        conversationID: widget.conversationID,
+        oldestMessagesID: _messages.firstMessageID);
+
+    // Mark as not loading anymore
+    _setLoadingOlderMessagesState(_OlderMessagesLevel.NONE);
+
+    // Check for errors
+    if (messages == null) {
+      _errorLoading();
+      return;
+    }
+
+    // Check if there is no more unread messages
+    if (messages.length == 0) {
+      _setLoadingOlderMessagesState(_OlderMessagesLevel.NO_MORE_AVAILABLE);
+      return;
+    }
+
+    // Apply the messages
+    _applyNewMessages(messages);
+  }
+
+  /// Apply new messages [messages] must not be null
+  Future<void> _applyNewMessages(ConversationMessagesList messages) async {
+
+    // We ignore new messages once the area is no longer visible
+    if(!this.mounted) return;
+
     //Then get information about users
     final usersToGet =
         findMissingFromList(_usersInfo.usersID, messages.getUsersID());
@@ -204,10 +259,19 @@ class _ConversationScreenState extends State<ConversationScreen> {
     return buildErrorCard(tr("Could not load the list of messages!"));
   }
 
+  /// Widget shown when loading older messages
+  Widget _buildLoadingOlderMessage() {
+    return Container(
+      padding: EdgeInsets.all(8.0),
+      child: CircularProgressIndicator(),
+    );
+  }
+
   /// Messages list
   Widget _buildMessagesList() {
     return Expanded(
       child: ListView.builder(
+          controller: _scrollController,
           reverse: true,
           itemCount: _messages.length,
           itemBuilder: (c, i) {
@@ -221,7 +285,7 @@ class _ConversationScreenState extends State<ConversationScreen> {
     );
   }
 
-  /// Send message from
+  /// Send message form
   Widget _buildSendMessageForm() {
     return new Container(
       margin: const EdgeInsets.symmetric(horizontal: 8.0),
@@ -244,6 +308,7 @@ class _ConversationScreenState extends State<ConversationScreen> {
           // Message area
           new Flexible(
             child: new TextField(
+              keyboardType: TextInputType.text,
               maxLines: null,
               maxLength: 200,
               maxLengthEnforced: true,
@@ -302,10 +367,17 @@ class _ConversationScreenState extends State<ConversationScreen> {
         Container(
           child: _error == ErrorLevel.MINOR ? _buildError() : null,
         ),
+        Container(
+          child: _loadingOlderMessages == _OlderMessagesLevel.LOADING
+              ? _buildLoadingOlderMessage()
+              : null,
+        ),
         _buildMessagesList(),
         Divider(),
         _buildSendMessageForm()
       ],
     );
   }
+
+
 }