Refactored MaterialApp (#3475)

* Refactored MaterialApp

packages/flutter/lib/src/material/app.dart

@@ -25,68 +25,45 @@ const TextStyle _errorTextStyle = const TextStyle(
 /// An application that uses material design.
 ///
 /// A convenience widget that wraps a number of widgets that are commonly
-/// required for material design applications. It builds upon
+/// required for material design applications. It builds upon a
 /// [WidgetsApp] by adding material-design specific functionality, such as
 /// [AnimatedTheme] and [GridPaper]. This widget also configures the top-level
-/// [Navigator] to perform [Hero] animations.
+/// [Navigator]'s observer to perform [Hero] animations.
 ///
 /// See also:
 ///
 ///  * [WidgetsApp]
 ///  * [Scaffold]
 ///  * [MaterialPageRoute]
-class MaterialApp extends WidgetsApp {
+class MaterialApp extends StatefulWidget {
+
   /// Creates a MaterialApp.
   ///
   /// At least one of [home], [routes], or [onGenerateRoute] must be
   /// given. If only [routes] is given, it must include an entry for
   /// the [Navigator.defaultRouteName] (`'/'`).
   ///
-  /// See also the [new WidgetsApp] constructor (which this extends).
+  /// This class creates an instance of [WidgetsApp].
   MaterialApp({
     Key key,
-    String title,
-    ThemeData theme,
-    Widget home,
-    Map<String, WidgetBuilder> routes: const <String, WidgetBuilder>{},
-    RouteFactory onGenerateRoute,
-    LocaleChangedCallback onLocaleChanged,
+    this.title,
+    this.theme,
+    this.home,
+    this.routes: const <String, WidgetBuilder>{},
+    this.onGenerateRoute,
+    this.onLocaleChanged,
     this.debugShowMaterialGrid: false,
-    bool showPerformanceOverlay: false,
-    bool showSemanticsDebugger: false,
-    bool debugShowCheckedModeBanner: true
-  }) : theme = theme,
-       home = home,
-       routes = routes,
-       super(
-    key: key,
-    title: title,
-    textStyle: _errorTextStyle,
-    color: theme?.primaryColor ?? Colors.blue[500], // blue[500] is the primary color of the default theme
-    onGenerateRoute: (RouteSettings settings) {
-      WidgetBuilder builder = routes[settings.name];
-      if (builder == null && home != null && settings.name == Navigator.defaultRouteName)
-        builder = (BuildContext context) => home;
-      if (builder != null) {
-        return new MaterialPageRoute<Null>(
-          builder: builder,
-          settings: settings
-        );
-      }
-      if (onGenerateRoute != null)
-        return onGenerateRoute(settings);
-      return null;
-    },
-    onLocaleChanged: onLocaleChanged,
-    showPerformanceOverlay: showPerformanceOverlay,
-    showSemanticsDebugger: showSemanticsDebugger,
-    debugShowCheckedModeBanner: debugShowCheckedModeBanner
-  ) {
+    this.showPerformanceOverlay: false,
+    this.showSemanticsDebugger: false,
+    this.debugShowCheckedModeBanner: true
+  }) : super(key: key) {
     assert(debugShowMaterialGrid != null);
     assert(routes != null);
     assert(!routes.containsKey(Navigator.defaultRouteName) || (home == null));
     assert(routes.containsKey(Navigator.defaultRouteName) || (home != null) || (onGenerateRoute != null));
-  }
+ }
+  /// A one-line description of this app for use in the window manager.
+  final String title;
 
   /// The colors to use for the application's widgets.
   final ThemeData theme;
@@ -124,6 +101,37 @@ class MaterialApp extends WidgetsApp {
   /// build the page instead.
   final Map<String, WidgetBuilder> routes;
 
+  /// The route generator callback used when the app is navigated to a
+  /// named route.
+  final RouteFactory onGenerateRoute;
+
+  /// Callback that is invoked when the operating system changes the
+  /// current locale.
+  final LocaleChangedCallback onLocaleChanged;
+
+  /// Turns on a performance overlay.
+  /// https://flutter.io/debugging/#performanceoverlay
+  final bool showPerformanceOverlay;
+
+  /// Turns on an overlay that shows the accessibility information
+  /// reported by the framework.
+  final bool showSemanticsDebugger;
+
+  /// Turns on a little "SLOW MODE" banner in checked mode to indicate
+  /// that the app is in checked mode. This is on by default (in
+  /// checked mode), to turn it off, set the constructor argument to
+  /// false. In release mode this has no effect.
+  ///
+  /// To get this banner in your application if you're not using
+  /// WidgetsApp, include a [CheckedModeBanner] widget in your app.
+  ///
+  /// This banner is intended to deter people from complaining that your
+  /// app is slow when it's in checked mode. In checked mode, Flutter
+  /// enables a large number of expensive diagnostics to aid in
+  /// development, and so performance in checked mode is not
+  /// representative of what will happen in release mode.
+  final bool debugShowCheckedModeBanner;
+
   /// Turns on a [GridPaper] overlay that paints a baseline grid
   /// Material apps:
   /// https://www.google.com/design/spec/layout/metrics-keylines.html
@@ -134,11 +142,23 @@ class MaterialApp extends WidgetsApp {
   _MaterialAppState createState() => new _MaterialAppState();
 }
 
-class _MaterialAppState extends WidgetsAppState<MaterialApp> {
+class _MaterialAppState extends State<MaterialApp> {
   final HeroController _heroController = new HeroController();
 
-  @override
-  NavigatorObserver get navigatorObserver => _heroController;
+  Route<dynamic> _onGenerateRoute(RouteSettings settings) {
+    WidgetBuilder builder = config.routes[settings.name];
+    if (builder == null && config.home != null && settings.name == Navigator.defaultRouteName)
+      builder = (BuildContext context) => config.home;
+    if (builder != null) {
+      return new MaterialPageRoute<Null>(
+        builder: builder,
+        settings: settings
+      );
+    }
+    if (config.onGenerateRoute != null)
+      return config.onGenerateRoute(settings);
+    return null;
+  }
 
   @override
   Widget build(BuildContext context) {
@@ -146,8 +166,19 @@ class _MaterialAppState extends WidgetsAppState<MaterialApp> {
     Widget result = new AnimatedTheme(
       data: theme,
       duration: kThemeAnimationDuration,
-      child: super.build(context)
+      child: new WidgetsApp(
+        title: config.title,
+        textStyle: _errorTextStyle,
+        color: theme?.primaryColor ?? Colors.blue[500], // blue[500] is the primary color of the default theme
+        navigatorObserver: _heroController,
+        onGenerateRoute: _onGenerateRoute,
+        onLocaleChanged: config.onLocaleChanged,
+        showPerformanceOverlay: config.showPerformanceOverlay,
+        showSemanticsDebugger: config.showSemanticsDebugger,
+        debugShowCheckedModeBanner: config.debugShowCheckedModeBanner
+      )
     );
+
     assert(() {
       if (config.debugShowMaterialGrid) {
         result = new GridPaper(
@@ -160,7 +191,7 @@ class _MaterialAppState extends WidgetsAppState<MaterialApp> {
       }
       return true;
     });
+
     return result;
   }
-
 }

packages/flutter/lib/src/widgets/app.dart

@@ -37,6 +37,7 @@ class WidgetsApp extends StatefulWidget {
     this.title,
     this.textStyle,
     this.color,
+    this.navigatorObserver,
     this.onGenerateRoute,
     this.onLocaleChanged,
     this.showPerformanceOverlay: false,
@@ -92,6 +93,9 @@ class WidgetsApp extends StatefulWidget {
   /// representative of what will happen in release mode.
   final bool debugShowCheckedModeBanner;
 
+  /// The observer for the Navigator created for this app.
+  final NavigatorObserver navigatorObserver;
+
   static bool showPerformanceOverlayOverride = false;
 
   @override
@@ -151,8 +155,6 @@ class WidgetsAppState<T extends WidgetsApp> extends State<T> implements WidgetsB
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) { }
 
-  NavigatorObserver get navigatorObserver => null;
-
   @override
   Widget build(BuildContext context) {
     if (config.onLocaleChanged != null && _localeData == null) {
@@ -176,7 +178,7 @@ class WidgetsAppState<T extends WidgetsApp> extends State<T> implements WidgetsB
               key: _navigator,
               initialRoute: ui.window.defaultRouteName,
               onGenerateRoute: config.onGenerateRoute,
-              observer: navigatorObserver
+              observer: config.navigatorObserver
             )
           )
         )