experiment with streambuilder

packages/stream_chat_flutter_core/lib/src/better_stream_builder.dart

@@ -0,0 +1,100 @@
+import 'dart:async';
+
+import 'package:flutter/widgets.dart';
+
+class BetterStreamBuilder<T> extends StatefulWidget {
+  const BetterStreamBuilder({
+    required this.stream,
+    required this.initialData,
+    required this.builder,
+    this.loadingBuilder,
+    this.errorBuilder,
+    this.comparator,
+    Key? key,
+  }) : super(key: key);
+
+  final Stream<T>? stream;
+  final T initialData;
+  final bool Function(T?, T)? comparator;
+  final Widget Function(BuildContext context, T data) builder;
+  final Widget Function(BuildContext context)? loadingBuilder;
+  final Widget Function(BuildContext context, Object error)? errorBuilder;
+
+  @override
+  _BetterStreamBuilderState createState() => _BetterStreamBuilderState<T>();
+}
+
+class _BetterStreamBuilderState<T> extends State<BetterStreamBuilder<T>> {
+  Widget? _child;
+  T? _lastEvent;
+  StreamSubscription? _subscription;
+  Object? _lastError;
+
+  @override
+  Widget build(BuildContext context) => _child ?? const Offstage();
+
+  bool _firstTime = true;
+  @override
+  void didChangeDependencies() {
+    if (_firstTime) {
+      if (widget.initialData == null && widget.loadingBuilder != null) {
+        _child = widget.loadingBuilder!(context);
+      } else {
+        _onEvent(widget.initialData);
+      }
+      _lastEvent = widget.initialData;
+      _subscription = widget.stream?.listen(
+        _onEvent,
+        onError: _onError,
+      );
+
+      _firstTime = false;
+    }
+    super.didChangeDependencies();
+  }
+
+  @override
+  void didUpdateWidget(covariant BetterStreamBuilder<T> oldWidget) {
+    if (_lastError != null && oldWidget.errorBuilder != widget.errorBuilder) {
+      _onError(_lastError);
+    } else if (oldWidget.builder != widget.builder) {
+      _onEvent(_lastEvent);
+    }
+
+    if (oldWidget.stream != widget.stream) {
+      _subscription?.cancel();
+      _subscription = widget.stream?.listen(
+        _onEvent,
+        onError: _onError,
+      );
+    }
+    super.didUpdateWidget(oldWidget);
+  }
+
+  @override
+  void dispose() {
+    _subscription?.cancel();
+    super.dispose();
+  }
+
+  void _onError(error) {
+    if (widget.errorBuilder != null && error != _lastError) {
+      setState(() {
+        _child = widget.errorBuilder!(context, error);
+      });
+      _lastError = error;
+    }
+  }
+
+  void _onEvent(event) {
+    _lastError = null;
+    if (widget.comparator != null
+        ? widget.comparator!(_lastEvent, event)
+        : event != _lastEvent) {
+      setState(() {
+        _child = widget.builder(context, event);
+      });
+      _lastEvent = event;
+    }
+  }
+}

packages/stream_chat_flutter_core/lib/src/message_list_core.dart

@@ -1,9 +1,11 @@
 import 'dart:async';
 
+import 'package:collection/collection.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:stream_chat/stream_chat.dart';
+import 'package:stream_chat_flutter_core/src/better_stream_builder.dart';
 import 'package:stream_chat_flutter_core/src/stream_channel.dart';
 import 'package:stream_chat_flutter_core/src/typedef.dart';
 
@@ -127,6 +129,10 @@ class MessageListCoreState extends State<MessageListCore> {
             .map((threads) => threads[widget.parentMessage!.id])
         : _streamChannel!.channel.state?.messagesStream;
 
+    final initialData = _isThreadConversation
+        ? _streamChannel!.channel.state?.threads[widget.parentMessage!.id]
+        : _streamChannel!.channel.state?.messages;
+
     bool defaultFilter(Message m) {
       final isMyMessage = m.user?.id == _currentUser?.id;
       final isDeletedOrShadowed = m.isDeleted == true || m.shadowed == true;
@@ -134,30 +140,27 @@ class MessageListCoreState extends State<MessageListCore> {
       return true;
     }
 
-    return StreamBuilder<List<Message>?>(
-      stream: messagesStream?.map(
+    return BetterStreamBuilder<List<Message>?>(
+      initialData: initialData,
+      comparator: const ListEquality().equals,
+      stream: messagesStream!.map(
         (messages) =>
             messages?.where(widget.messageFilter ?? defaultFilter).toList(
                   growable: false,
                 ),
       ),
+      errorBuilder: widget.errorWidgetBuilder,
+      loadingBuilder: widget.loadingBuilder,
       builder: (context, snapshot) {
-        if (snapshot.hasError) {
-          return widget.errorWidgetBuilder(context, snapshot.error!);
-        } else if (!snapshot.hasData) {
-          return widget.loadingBuilder(context);
-        } else {
-          final messageList =
-              snapshot.data?.reversed.toList(growable: false) ?? [];
-          if (messageList.isEmpty && !_isThreadConversation) {
-            if (_upToDate) {
-              return widget.emptyBuilder(context);
-            }
-          } else {
-            _messages = messageList;
+        final messageList = snapshot?.reversed.toList(growable: false) ?? [];
+        if (messageList.isEmpty && !_isThreadConversation) {
+          if (_upToDate) {
+            return widget.emptyBuilder(context);
           }
-          return widget.messageListBuilder(context, _messages);
+        } else {
+          _messages = messageList;
         }
+        return widget.messageListBuilder(context, _messages);
       },
     );
   }

packages/stream_chat_flutter_core/lib/stream_chat_flutter_core.dart

@@ -2,6 +2,7 @@ library stream_chat_flutter_core;
 
 export 'package:stream_chat/stream_chat.dart';
 
+export 'src/better_stream_builder.dart';
 export 'src/channel_list_core.dart' hide ChannelListCoreState;
 export 'src/channels_bloc.dart';
 export 'src/lazy_load_scroll_view.dart';