From 7d362db390d00bde1b0f2a1af4e998bda218a2f8 Mon Sep 17 00:00:00 2001
From: Deven Joshi <deven9852@gmail.com>
Date: Fri, 17 Sep 2021 18:34:00 +0530
Subject: [PATCH] fix(ui): check scrollController is attached before calling
 jump.

---
 .../lib/src/message_list_view.dart            | 10 ++--
 .../test/src/message_list_view_test.dart      | 49 +++++++++++++++++++
 2 files changed, 55 insertions(+), 4 deletions(-)
 create mode 100644 packages/stream_chat_flutter/test/src/message_list_view_test.dart

diff --git a/packages/stream_chat_flutter/lib/src/message_list_view.dart b/packages/stream_chat_flutter/lib/src/message_list_view.dart
index e325598d..c6786a4b 100644
--- a/packages/stream_chat_flutter/lib/src/message_list_view.dart
+++ b/packages/stream_chat_flutter/lib/src/message_list_view.dart
@@ -1199,10 +1199,12 @@ class _MessageListViewState extends State<MessageListView> {
       initialAlignment = _initialAlignment;
 
       WidgetsBinding.instance!.addPostFrameCallback((timeStamp) {
-        _scrollController?.jumpTo(
-          index: initialIndex,
-          alignment: initialAlignment,
-        );
+        if (_scrollController?.isAttached ?? false) {
+          _scrollController?.jumpTo(
+            index: initialIndex,
+            alignment: initialAlignment,
+          );
+        }
       });
 
       _messageNewListener =
diff --git a/packages/stream_chat_flutter/test/src/message_list_view_test.dart b/packages/stream_chat_flutter/test/src/message_list_view_test.dart
new file mode 100644
index 00000000..8217f6de
--- /dev/null
+++ b/packages/stream_chat_flutter/test/src/message_list_view_test.dart
@@ -0,0 +1,49 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:stream_chat_flutter/stream_chat_flutter.dart';
+
+import 'mocks.dart';
+
+void main() {
+  late StreamChatClient client;
+  late Channel channel;
+
+  setUp(() {
+    client = MockClient();
+    channel = MockChannel();
+    when(() => channel.on(any(), any(), any(), any()))
+        .thenAnswer((_) => const Stream.empty());
+    final channelClientState = MockChannelState();
+    when(() => channel.state).thenReturn(channelClientState);
+    when(() => channelClientState.threadsStream)
+        .thenAnswer((_) => const Stream.empty());
+    when(() => channelClientState.messagesStream)
+        .thenAnswer((_) => const Stream.empty());
+    when(() => channelClientState.messages).thenReturn([]);
+    when(() => channelClientState.isUpToDate).thenReturn(true);
+  });
+
+  // https://github.com/GetStream/stream-chat-flutter/issues/674
+  testWidgets('renders empty message list view', (tester) async {
+    const emptyWidgetKey = Key('empty_widget');
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: StreamChat(
+          client: client,
+          child: StreamChannel(
+            channel: channel,
+            child: MessageListView(
+              emptyBuilder: (_) => Container(key: emptyWidgetKey),
+            ),
+          ),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    expect(find.byType(MessageListView), findsOneWidget);
+    expect(find.byKey(emptyWidgetKey), findsOneWidget);
+  });
+}