Can get older posts on latest posts page

lib/helpers/posts_helper.dart

@@ -39,12 +39,13 @@ const _APIUserAccessMap = {
 class PostsHelper {
   /// Get the list of latest posts. Return the list of posts or null in case of
   /// failure
-  Future<PostsList> getLatest() async {
+  Future<PostsList> getLatest({int from = 0}) async {
     final response = await APIRequest(
       uri: "posts/get_latest",
       needLogin: true,
       args: {
-        "include_groups": true.toString()
+        "include_groups": true.toString(),
+        "startFrom": from.toString(),
       }
     ).exec();
 

lib/lists/posts_list.dart

@@ -46,4 +46,12 @@ class PostsList extends ListBase<Post> {
 
     return set;
   }
+
+  /// Get the ID of the oldest post of this list. Returns 0 if the list is empty
+  int get oldestID {
+    if(isEmpty)
+      return 0;
+
+    return this.elementAt(length - 1).id;
+  }
 }

lib/ui/screens/newest_posts.dart

@@ -20,6 +20,7 @@ class _NewestPostsScreenState extends State<NewestPostsScreen> {
   Widget build(BuildContext context) {
     return PostsListWidget(
       getPostsList: _postsHelper.getLatest,
+      getOlder: (f) => _postsHelper.getLatest(from: f - 1),
       showPostsTarget: true,
     );
   }

lib/ui/widgets/posts_list_widget.dart

@@ -6,6 +6,7 @@ import 'package:comunic/lists/users_list.dart';
 import 'package:comunic/models/post.dart';
 import 'package:comunic/ui/screens/conversation_screen.dart';
 import 'package:comunic/ui/tiles/post_tile.dart';
+import 'package:comunic/ui/widgets/scroll_watcher.dart';
 import 'package:comunic/utils/intl_utils.dart';
 import 'package:comunic/utils/ui_utils.dart';
 import 'package:flutter/material.dart';
@@ -18,6 +19,7 @@ import 'package:flutter/material.dart';
 
 class PostsListWidget extends StatefulWidget {
   final Future<PostsList> Function() getPostsList;
+  final Future<PostsList> Function(int from) getOlder;
   final bool showPostsTarget;
   final bool buildListView;
   final bool userNamesClickable;
@@ -28,6 +30,7 @@ class PostsListWidget extends StatefulWidget {
     @required this.showPostsTarget,
     this.userNamesClickable = true,
     this.buildListView = true,
+    this.getOlder,
   })  : assert(getPostsList != null),
         assert(showPostsTarget != null),
         assert(buildListView != null),
@@ -47,10 +50,17 @@ class _PostsListWidgetState extends State<PostsListWidget> {
   PostsList _list;
   UsersList _users;
   GroupsList _groups;
+  ScrollWatcher _scrollController;
+  ErrorLevel _error = ErrorLevel.NONE;
 
   set error(ErrorLevel err) => setState(() => _error = err);
 
-  ErrorLevel _error = ErrorLevel.NONE;
+  @override
+  void initState() {
+    super.initState();
+
+    _scrollController = ScrollWatcher(onReachBottom: _reachedPostsBottom);
+  }
 
   @override
   void didChangeDependencies() {
@@ -62,8 +72,10 @@ class _PostsListWidgetState extends State<PostsListWidget> {
       error = _list == null ? ErrorLevel.MAJOR : ErrorLevel.MINOR;
 
   /// Load the list of posts
-  Future<void> _loadPostsList() async {
-    final list = await widget.getPostsList();
+  Future<void> _loadPostsList({bool getOlder = false}) async {
+    final list = !getOlder
+        ? await widget.getPostsList()
+        : await widget.getOlder(_list.oldestID);
 
     if (list == null) return _loadError();
 
@@ -76,9 +88,15 @@ class _PostsListWidgetState extends State<PostsListWidget> {
     if (groups == null) return _loadError();
 
     setState(() {
+      if (!getOlder) {
         _list = list;
         _users = users;
         _groups = groups;
+      } else {
+        _list.addAll(list);
+        _users.addAll(users);
+        _groups.addAll(groups);
+      }
     });
   }
 
@@ -99,6 +117,7 @@ class _PostsListWidgetState extends State<PostsListWidget> {
     return ListView.builder(
       itemCount: _list.length,
       itemBuilder: _buildItem,
+      controller: _scrollController,
     );
   }
 
@@ -131,4 +150,8 @@ class _PostsListWidgetState extends State<PostsListWidget> {
   }
 
   void _removePost(Post post) => setState(() => _list.remove(post));
+
+  void _reachedPostsBottom() {
+    if (widget.getOlder != null) _loadPostsList(getOlder: true);
+  }
 }