migrate example

packages/stream_chat/example/lib/main.dart

@@ -44,9 +44,9 @@ class StreamExample extends StatelessWidget {
   /// To initialize this example, an instance of
   /// [client] and [channel] is required.
   const StreamExample({
-    Key key,
-    @required this.client,
-    @required this.channel,
+    Key? key,
+    required this.client,
+    required this.channel,
   }) : super(key: key);
 
   /// Instance of [StreamChatClient] we created earlier.
@@ -69,28 +69,31 @@ class StreamExample extends StatelessWidget {
 /// containing the channel name and a [MessageView] displaying recent messages.
 class HomeScreen extends StatelessWidget {
   /// [HomeScreen] is constructed using the [Channel] we defined earlier.
-  const HomeScreen({Key key, @required this.channel}) : super(key: key);
+  const HomeScreen({
+    Key? key,
+    required this.channel,
+  }) : super(key: key);
 
   /// Channel object containing the [Channel.id] we'd like to observe.
   final Channel channel;
 
   @override
   Widget build(BuildContext context) {
-    final messages = channel.state.channelStateStream;
+    final messages = channel.state!.channelStateStream;
     return Scaffold(
       appBar: AppBar(
         title: Text('Channel: ${channel.id}'),
       ),
       body: SafeArea(
-        child: StreamBuilder<ChannelState>(
+        child: StreamBuilder<ChannelState?>(
           stream: messages,
           builder: (
             BuildContext context,
-            AsyncSnapshot<ChannelState> snapshot,
+            AsyncSnapshot<ChannelState?> snapshot,
           ) {
             if (snapshot.hasData && snapshot.data != null) {
               return MessageView(
-                messages: snapshot.data.messages.reversed.toList(),
+                messages: snapshot.data!.messages.reversed.toList(),
                 channel: channel,
               );
             } else if (snapshot.hasError) {
@@ -119,9 +122,9 @@ class HomeScreen extends StatelessWidget {
 class MessageView extends StatefulWidget {
   /// Message takes the latest list of messages and the current channel.
   const MessageView({
-    Key key,
-    @required this.messages,
-    @required this.channel,
+    Key? key,
+    required this.messages,
+    required this.channel,
   }) : super(key: key);
 
   /// List of messages sent in the given channel.
@@ -135,8 +138,8 @@ class MessageView extends StatefulWidget {
 }
 
 class _MessageViewState extends State<MessageView> {
-  TextEditingController _controller;
-  ScrollController _scrollController;
+  late final TextEditingController _controller;
+  late final ScrollController _scrollController;
 
   List<Message> get _messages => widget.messages;
 
@@ -174,12 +177,12 @@ class _MessageViewState extends State<MessageView> {
             reverse: true,
             itemBuilder: (BuildContext context, int index) {
               final item = _messages[index];
-              if (item.user.id == widget.channel.client.uid) {
+              if (item.user?.id == widget.channel.client.uid) {
                 return Align(
                   alignment: Alignment.centerRight,
                   child: Padding(
                     padding: const EdgeInsets.all(8),
-                    child: Text(item.text),
+                    child: Text(item.text ?? ''),
                   ),
                 );
               } else {
@@ -187,7 +190,7 @@ class _MessageViewState extends State<MessageView> {
                   alignment: Alignment.centerLeft,
                   child: Padding(
                     padding: const EdgeInsets.all(8),
-                    child: Text(item.text),
+                    child: Text(item.text ?? ''),
                   ),
                 );
               }
@@ -246,5 +249,5 @@ class _MessageViewState extends State<MessageView> {
 /// Helper extension for quickly retrieving
 /// the current user id from a [StreamChatClient].
 extension on StreamChatClient {
-  String get uid => state.user.id;
+  String get uid => state.user!.id;
 }

packages/stream_chat/example/pubspec.yaml

@@ -5,7 +5,7 @@ publish_to: "none"
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   cupertino_icons: ^1.0.0