Add flutter_lints to add_to_app/plugin/flutter_module_using_plugin (#812)

add_to_app/plugin/flutter_module_using_plugin/lib/cell.dart

@@ -11,12 +11,14 @@ import 'package:sensors/sensors.dart';
 // This is on alternate entrypoint for this module to display Flutter UI in
 // a (multi-)view integration scenario.
 void main() {
-  runApp(Cell());
+  runApp(const Cell());
 }
 
 class Cell extends StatefulWidget {
+  const Cell({Key key}) : super(key: key);
+
   @override
-  State<StatefulWidget> createState() => new _CellState();
+  State<StatefulWidget> createState() => _CellState();
 }
 
 class _CellState extends State<Cell> with WidgetsBindingObserver {
@@ -29,8 +31,8 @@ class _CellState extends State<Cell> with WidgetsBindingObserver {
 
   @override
   void initState() {
-    final channel = MethodChannel('dev.flutter.example/cell');
-    channel.setMethodCallHandler((MethodCall call) async {
+    const channel = MethodChannel('dev.flutter.example/cell');
+    channel.setMethodCallHandler((call) async {
       if (call.method == 'setCellNumber') {
         setState(() {
           cellNumber = call.arguments as int;
@@ -73,10 +75,10 @@ class _CellState extends State<Cell> with WidgetsBindingObserver {
       home: Container(
         color: Colors.white,
         child: Builder(
-          builder: (BuildContext context) {
+          builder: (context) {
             return Card(
               // Mimic the platform Material look.
-              margin: EdgeInsets.symmetric(horizontal: 36, vertical: 24),
+              margin: const EdgeInsets.symmetric(horizontal: 36, vertical: 24),
               shape: RoundedRectangleBorder(
                 borderRadius: BorderRadius.circular(16),
               ),
@@ -103,15 +105,14 @@ class _CellState extends State<Cell> with WidgetsBindingObserver {
                     bottom: 0,
                     child: Opacity(
                       opacity: 0.2,
-                      child: StreamBuilder(
+                      child: StreamBuilder<AccelerometerEvent>(
                         // Don't continuously rebuild for nothing when the
                         // cell isn't visible.
                         stream: appLifecycleState == AppLifecycleState.resumed
                             ? accelerometerEvents
                             : Stream.value(defaultPosition),
                         initialData: defaultPosition,
-                        builder: (BuildContext context,
-                            AsyncSnapshot<AccelerometerEvent> snapshot) {
+                        builder: (context, snapshot) {
                           return Transform(
                               // Figure out the phone's orientation relative
                               // to gravity's direction. Ignore the z vector.
@@ -120,7 +121,7 @@ class _CellState extends State<Cell> with WidgetsBindingObserver {
                                 ..multiply(Matrix4.rotationY(
                                     snapshot.data.x / gravity * pi / 2)),
                               alignment: Alignment.center,
-                              child: FlutterLogo(size: 72));
+                              child: const FlutterLogo(size: 72));
                         },
                       ),
                     ),

add_to_app/plugin/flutter_module_using_plugin/lib/main.dart

@@ -20,7 +20,7 @@ void main() {
   runApp(
     ChangeNotifierProvider.value(
       value: model,
-      child: MyApp(),
+      child: const MyApp(),
     ),
   );
 }
@@ -30,7 +30,7 @@ void main() {
 // This is unfortunately in this file due to
 // https://github.com/flutter/flutter/issues/72630.
 void showCell() {
-  runApp(Cell());
+  runApp(const Cell());
 }
 
 /// A simple model that uses a [MethodChannel] as the source of truth for the
@@ -43,17 +43,17 @@ void showCell() {
 class CounterModel extends ChangeNotifier {
   CounterModel() {
     _channel.setMethodCallHandler(_handleMessage);
-    _channel.invokeMethod('requestCounter');
+    _channel.invokeMethod<void>('requestCounter');
   }
 
-  final _channel = MethodChannel('dev.flutter.example/counter');
+  final _channel = const MethodChannel('dev.flutter.example/counter');
 
   int _count = 0;
 
   int get count => _count;
 
   void increment() {
-    _channel.invokeMethod('incrementCounter');
+    _channel.invokeMethod<void>('incrementCounter');
   }
 
   Future<dynamic> _handleMessage(MethodCall call) async {
@@ -69,13 +69,15 @@ class CounterModel extends ChangeNotifier {
 /// It offers two routes, one suitable for displaying as a full screen and
 /// another designed to be part of a larger UI.
 class MyApp extends StatelessWidget {
+  const MyApp({Key key}) : super(key: key);
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
       title: 'Flutter Module Title',
       routes: {
-        '/': (context) => FullScreenView(),
-        '/mini': (context) => Contents(),
+        '/': (context) => const FullScreenView(),
+        '/mini': (context) => const Contents(),
       },
     );
   }
@@ -84,11 +86,13 @@ class MyApp extends StatelessWidget {
 /// Wraps [Contents] in a Material [Scaffold] so it looks correct when displayed
 /// full-screen.
 class FullScreenView extends StatelessWidget {
+  const FullScreenView({Key key}) : super(key: key);
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: Text('Full-screen Flutter with plugin'),
+        title: const Text('Full-screen Flutter with plugin'),
       ),
       body: const Contents(showExit: true),
     );
@@ -104,7 +108,7 @@ class FullScreenView extends StatelessWidget {
 class Contents extends StatelessWidget {
   final bool showExit;
 
-  const Contents({this.showExit = false});
+  const Contents({this.showExit = false, Key key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
@@ -120,7 +124,7 @@ class Contents extends StatelessWidget {
               ),
             ),
           ),
-          Positioned.fill(
+          const Positioned.fill(
             child: Opacity(
               opacity: .25,
               child: FittedBox(
@@ -138,7 +142,7 @@ class Contents extends StatelessWidget {
                   '${mediaInfo.size.height.toStringAsFixed(1)}',
                   style: Theme.of(context).textTheme.headline5,
                 ),
-                SizedBox(height: 16),
+                const SizedBox(height: 16),
                 Consumer<CounterModel>(
                   builder: (context, model, child) {
                     return Text(
@@ -147,12 +151,12 @@ class Contents extends StatelessWidget {
                     );
                   },
                 ),
-                SizedBox(height: 16),
+                const SizedBox(height: 16),
                 Consumer<CounterModel>(
                   builder: (context, model, child) {
                     return ElevatedButton(
                       onPressed: () => model.increment(),
-                      child: Text('Tap me!'),
+                      child: const Text('Tap me!'),
                     );
                   },
                 ),
@@ -160,18 +164,18 @@ class Contents extends StatelessWidget {
                   onPressed: () async {
                     // Use the url_launcher plugin to open the Flutter docs in
                     // a browser.
-                    final url = 'https://flutter.dev/docs';
+                    const url = 'https://flutter.dev/docs';
                     if (await launcher.canLaunch(url)) {
                       launcher.launch(url);
                     }
                   },
-                  child: Text('Open Flutter Docs'),
+                  child: const Text('Open Flutter Docs'),
                 ),
                 if (showExit) ...[
-                  SizedBox(height: 16),
+                  const SizedBox(height: 16),
                   ElevatedButton(
                     onPressed: () => SystemNavigator.pop(),
-                    child: Text('Exit this screen'),
+                    child: const Text('Exit this screen'),
                   ),
                 ],
               ],