Migrate remaining examples to null-safety (#74857)

dev/bots/test.dart

@@ -666,7 +666,7 @@ Future<void> _runFrameworkTests() async {
     await _runFlutterTest(path.join(flutterRoot, 'dev', 'integration_tests', 'android_semantics_testing'));
     await _runFlutterTest(path.join(flutterRoot, 'dev', 'manual_tests'));
     await _runFlutterTest(path.join(flutterRoot, 'dev', 'tools', 'vitool'));
-    await _runFlutterTest(path.join(flutterRoot, 'examples', 'hello_world'));
+    await _runFlutterTest(path.join(flutterRoot, 'examples', 'hello_world'), options: soundNullSafetyOptions);
     await _runFlutterTest(path.join(flutterRoot, 'examples', 'layers'), options: soundNullSafetyOptions);
     await _runFlutterTest(path.join(flutterRoot, 'dev', 'benchmarks', 'test_apps', 'stocks'));
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_driver'), tests: <String>[path.join('test', 'src', 'real_tests')]);

examples/flutter_view/lib/main.dart

@@ -11,7 +11,6 @@ void main() {
 }
 
 class FlutterView extends StatelessWidget {
-
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
@@ -33,8 +32,8 @@ class _MyHomePageState extends State<MyHomePage> {
   static const String _channel = 'increment';
   static const String _pong = 'pong';
   static const String _emptyMessage = '';
-  static const BasicMessageChannel<String> platform =
-      BasicMessageChannel<String>(_channel, StringCodec());
+  static const BasicMessageChannel<String?> platform =
+      BasicMessageChannel<String?>(_channel, StringCodec());
 
   int _counter = 0;
 
@@ -44,7 +43,7 @@ class _MyHomePageState extends State<MyHomePage> {
     platform.setMessageHandler(_handlePlatformIncrement);
   }
 
-  Future<String> _handlePlatformIncrement(String message) async {
+  Future<String> _handlePlatformIncrement(String? message) async {
     setState(() {
       _counter++;
     });

examples/flutter_view/pubspec.yaml

@@ -2,7 +2,7 @@ name: flutter_view
 description: A new flutter project.
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter:

examples/image_list/lib/main.dart

@@ -81,7 +81,7 @@ mhBKvYQc85gja0s1c+1VXA==
 
 class MyHttpOverrides extends HttpOverrides {
   @override
-  HttpClient createHttpClient(SecurityContext context) {
+  HttpClient createHttpClient(SecurityContext? context) {
     return super.createHttpClient(
         (context ?? SecurityContext())..setTrustedCertificatesBytes(certificate.codeUnits)
     );
@@ -141,7 +141,7 @@ class MyApp extends StatelessWidget {
 }
 
 class MyHomePage extends StatefulWidget {
-  const MyHomePage({Key key, this.title, this.port}) : super(key: key);
+  const MyHomePage({Key? key, required this.title, required this.port}) : super(key: key);
   final String title;
   final int port;
 
@@ -164,7 +164,7 @@ class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
         frameBuilder: (
           BuildContext context,
           Widget child,
-          int frame,
+          int? frame,
           bool wasSynchronouslyLoaded,
         ) {
           if (frame == 0 && !completer.isCompleted) {
@@ -177,17 +177,17 @@ class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
 
   @override
   Widget build(BuildContext context) {
-    final List<AnimationController> controllers = List<AnimationController>.filled(IMAGES, null);
-    for (int i = 0; i < IMAGES; i++) {
-      controllers[i] = AnimationController(
-        duration: const Duration(milliseconds: 3600),
-        vsync: this,
-      )..repeat();
-    }
-    final List<Completer<bool>> completers = List<Completer<bool>>.filled(IMAGES, null);
-    for (int i = 0; i < IMAGES; i++) {
-      completers[i] = Completer<bool>();
-    }
+    final List<AnimationController> controllers = <AnimationController>[
+      for (int i = 0; i < IMAGES; i++)
+        AnimationController(
+          duration: const Duration(milliseconds: 3600),
+          vsync: this,
+        )..repeat(),
+    ];
+    final List<Completer<bool>> completers = <Completer<bool>>[
+      for (int i = 0; i < IMAGES; i++)
+        Completer<bool>(),
+    ];
     final List<Future<bool>> futures = completers.map(
         (Completer<bool> completer) => completer.future).toList();
     final DateTime started = DateTime.now();

examples/image_list/pubspec.yaml

@@ -4,7 +4,7 @@ description: Simple Flutter project used for benchmarking image loading over net
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter:

examples/platform_channel/lib/main.dart

@@ -24,7 +24,7 @@ class _PlatformChannelState extends State<PlatformChannel> {
   Future<void> _getBatteryLevel() async {
     String batteryLevel;
     try {
-      final int result = await methodChannel.invokeMethod('getBatteryLevel');
+      final int? result = await methodChannel.invokeMethod('getBatteryLevel');
       batteryLevel = 'Battery level: $result%.';
     } on PlatformException {
       batteryLevel = 'Failed to get battery level.';
@@ -40,7 +40,7 @@ class _PlatformChannelState extends State<PlatformChannel> {
     eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
   }
 
-  void _onEvent(Object event) {
+  void _onEvent(Object? event) {
     setState(() {
       _chargingStatus =
           "Battery status: ${event == 'charging' ? '' : 'dis'}charging.";

examples/platform_channel/pubspec.yaml

 name: platform_channel
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter:

examples/platform_channel/test_driver/button_tap_test.dart

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// TODO(goderbauer): migrate this file to null-safety when flutter_driver is null-safe.
+// @dart = 2.9
+
 import 'package:flutter_driver/flutter_driver.dart';
 import 'package:test/test.dart' hide TypeMatcher, isInstanceOf;
 

examples/platform_channel_swift/lib/main.dart

@@ -24,7 +24,7 @@ class _PlatformChannelState extends State<PlatformChannel> {
   Future<void> _getBatteryLevel() async {
     String batteryLevel;
     try {
-      final int result = await methodChannel.invokeMethod('getBatteryLevel');
+      final int? result = await methodChannel.invokeMethod('getBatteryLevel');
       batteryLevel = 'Battery level: $result%.';
     } on PlatformException {
       batteryLevel = 'Failed to get battery level.';
@@ -40,7 +40,7 @@ class _PlatformChannelState extends State<PlatformChannel> {
     eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
   }
 
-  void _onEvent(Object event) {
+  void _onEvent(Object? event) {
     setState(() {
       _chargingStatus =
           "Battery status: ${event == 'charging' ? '' : 'dis'}charging.";

examples/platform_channel_swift/pubspec.yaml

 name: platform_channel_swift
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter:

examples/platform_channel_swift/test_driver/button_tap_test.dart

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// TODO(goderbauer): migrate this file to null-safety when flutter_driver is null-safe.
+// @dart = 2.9
+
 import 'package:flutter_driver/flutter_driver.dart';
 import 'package:test/test.dart' hide TypeMatcher, isInstanceOf;
 

examples/platform_view/lib/main.dart

@@ -25,7 +25,7 @@ class PlatformView extends StatelessWidget {
 }
 
 class MyHomePage extends StatefulWidget {
-  const MyHomePage({Key key, this.title}) : super(key: key);
+  const MyHomePage({Key? key, required this.title}) : super(key: key);
 
   final String title;
 
@@ -46,10 +46,10 @@ class _MyHomePageState extends State<MyHomePage> {
   }
 
   Future<void> _launchPlatformCount() async {
-    final int platformCounter =
+    final int? platformCounter =
         await _methodChannel.invokeMethod('switchView', _counter);
     setState(() {
-      _counter = platformCounter;
+      _counter = platformCounter!;
     });
   }
 

examples/platform_view/pubspec.yaml

 name: platform_view
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter:

examples/splash/pubspec.yaml

 name: splash
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter: