Implemented Dark Mode for Android (#25525) (#26605)

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

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:ui' as ui;
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
@@ -96,6 +98,7 @@ class MaterialApp extends StatefulWidget {
     this.onGenerateTitle,
     this.color,
     this.theme,
+    this.darkTheme,
     this.locale,
     this.localizationsDelegates,
     this.localeListResolutionCallback,
@@ -163,9 +166,44 @@ class MaterialApp extends StatefulWidget {
   /// This value is passed unmodified to [WidgetsApp.onGenerateTitle].
   final GenerateAppTitle onGenerateTitle;
 
-  /// The colors to use for the application's widgets.
+  /// Default visual properties, like colors fonts and shapes, for this app's
+  /// material widgets.
+  ///
+  /// A second [darkTheme] [ThemeData] value, which is used when the underlying
+  /// platform requests a "dark mode" UI, can also be specified.
+  ///
+  /// The default value of this property is the value of [ThemeData.light()].
+  ///
+  /// See also:
+  ///
+  ///  * [MediaQueryData.platformBrightness], which indicates the platform's
+  ///    desired brightness and is used to automatically toggle between [theme]
+  ///    and [darkTheme] in [MaterialApp].
+  ///  * [ThemeData.brightness], which indicates the [Brightness] of a theme's
+  ///    colors.
   final ThemeData theme;
 
+  /// The [ThemeData] to use when the platform specifically requests a dark
+  /// themed UI.
+  ///
+  /// Host platforms such as Android Pie can request a system-wide "dark mode"
+  /// when entering battery saver mode.
+  ///
+  /// When the host platform requests a [Brightness.dark] mode, you may want to
+  /// supply a [ThemeData.brightness] that's also [Brightness.dark].
+  ///
+  /// Uses [theme] instead when null. Defaults to the value of
+  /// [ThemeData.light()] when both [darkTheme] and [theme] are null.
+  ///
+  /// See also:
+  ///
+  ///  * [MediaQueryData.platformBrightness], which indicates the platform's
+  ///    desired brightness and is used to automatically toggle between [theme]
+  ///    and [darkTheme] in [MaterialApp].
+  ///  * [ThemeData.brightness], which is typically set to the value of
+  ///    [MediaQueryData.platformBrightness].
+  final ThemeData darkTheme;
+
   /// {@macro flutter.widgets.widgetsApp.color}
   final Color color;
 
@@ -403,45 +441,80 @@ class _MaterialAppState extends State<MaterialApp> {
 
   @override
   Widget build(BuildContext context) {
-    final ThemeData theme = widget.theme ?? ThemeData.fallback();
-    Widget result = AnimatedTheme(
-      data: theme,
-      isMaterialAppTheme: true,
-      child: WidgetsApp(
-        key: GlobalObjectKey(this),
-        navigatorKey: widget.navigatorKey,
-        navigatorObservers: _navigatorObservers,
+    Widget result = WidgetsApp(
+      key: GlobalObjectKey(this),
+      navigatorKey: widget.navigatorKey,
+      navigatorObservers: _navigatorObservers,
         pageRouteBuilder: <T>(RouteSettings settings, WidgetBuilder builder) =>
-          MaterialPageRoute<T>(settings: settings, builder: builder),
-        home: widget.home,
-        routes: widget.routes,
-        initialRoute: widget.initialRoute,
-        onGenerateRoute: widget.onGenerateRoute,
-        onUnknownRoute: widget.onUnknownRoute,
-        builder: widget.builder,
-        title: widget.title,
-        onGenerateTitle: widget.onGenerateTitle,
-        textStyle: _errorTextStyle,
-        // blue is the primary color of the default theme
-        color: widget.color ?? theme?.primaryColor ?? Colors.blue,
-        locale: widget.locale,
-        localizationsDelegates: _localizationsDelegates,
-        localeResolutionCallback: widget.localeResolutionCallback,
-        localeListResolutionCallback: widget.localeListResolutionCallback,
-        supportedLocales: widget.supportedLocales,
-        showPerformanceOverlay: widget.showPerformanceOverlay,
-        checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,
-        checkerboardOffscreenLayers: widget.checkerboardOffscreenLayers,
-        showSemanticsDebugger: widget.showSemanticsDebugger,
-        debugShowCheckedModeBanner: widget.debugShowCheckedModeBanner,
-        inspectorSelectButtonBuilder: (BuildContext context, VoidCallback onPressed) {
-          return FloatingActionButton(
-            child: const Icon(Icons.search),
-            onPressed: onPressed,
-            mini: true,
-          );
-        },
-      ),
+            MaterialPageRoute<T>(settings: settings, builder: builder),
+      home: widget.home,
+      routes: widget.routes,
+      initialRoute: widget.initialRoute,
+      onGenerateRoute: widget.onGenerateRoute,
+      onUnknownRoute: widget.onUnknownRoute,
+      builder: (BuildContext context, Widget child) {
+        // Use a light theme, dark theme, or fallback theme.
+        ThemeData theme;
+        final ui.Brightness platformBrightness = MediaQuery.platformBrightnessOf(context);
+        if (platformBrightness == ui.Brightness.dark && widget.darkTheme != null) {
+          theme = widget.darkTheme;
+        } else if (widget.theme != null) {
+          theme = widget.theme;
+        } else {
+          theme = ThemeData.fallback();
+        }
+
+        return AnimatedTheme(
+          data: theme,
+          isMaterialAppTheme: true,
+          child: widget.builder != null
+              ? Builder(
+                  builder: (BuildContext context) {
+                    // Why are we surrounding a builder with a builder?
+                    //
+                    // The widget.builder may contain code that invokes
+                    // Theme.of(), which should return the theme we selected
+                    // above in AnimatedTheme. However, if we invoke
+                    // widget.builder() directly as the child of AnimatedTheme
+                    // then there is no Context separating them, and the
+                    // widget.builder() will not find the theme. Therefore, we
+                    // surround widget.builder with yet another builder so that
+                    // a context separates them and Theme.of() correctly
+                    // resolves to the theme we passed to AnimatedTheme.
+                    return widget.builder(context, child);
+                  },
+                )
+              : child,
+        );
+      },
+      title: widget.title,
+      onGenerateTitle: widget.onGenerateTitle,
+      textStyle: _errorTextStyle,
+      // The color property is always pulled from the light theme, even if dark
+      // mode is activated. This was done to simplify the technical details
+      // of switching themes and it was deemed acceptable because this color
+      // property is only used on old Android OSes to color the app bar in
+      // Android's switcher UI.
+      //
+      // blue is the primary color of the default theme
+      color: widget.color ?? widget.theme?.primaryColor ?? Colors.blue,
+      locale: widget.locale,
+      localizationsDelegates: _localizationsDelegates,
+      localeResolutionCallback: widget.localeResolutionCallback,
+      localeListResolutionCallback: widget.localeListResolutionCallback,
+      supportedLocales: widget.supportedLocales,
+      showPerformanceOverlay: widget.showPerformanceOverlay,
+      checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,
+      checkerboardOffscreenLayers: widget.checkerboardOffscreenLayers,
+      showSemanticsDebugger: widget.showSemanticsDebugger,
+      debugShowCheckedModeBanner: widget.debugShowCheckedModeBanner,
+      inspectorSelectButtonBuilder: (BuildContext context, VoidCallback onPressed) {
+        return FloatingActionButton(
+          child: const Icon(Icons.search),
+          onPressed: onPressed,
+          mini: true,
+        );
+      },
     );
 
     assert(() {

packages/flutter/lib/src/rendering/binding.dart

@@ -33,6 +33,7 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
     window
       ..onMetricsChanged = handleMetricsChanged
       ..onTextScaleFactorChanged = handleTextScaleFactorChanged
+      ..onPlatformBrightnessChanged = handlePlatformBrightnessChanged
       ..onSemanticsEnabledChanged = _handleSemanticsEnabledChanged
       ..onSemanticsAction = _handleSemanticsAction;
     initRenderView();
@@ -168,6 +169,38 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
   @protected
   void handleTextScaleFactorChanged() { }
 
+  /// {@template on_platform_brightness_change}
+  /// Called when the platform brightness changes.
+  ///
+  /// The current platform brightness can be queried either from a Flutter
+  /// binding, or from a [MediaQuery] widget.
+  ///
+  /// ## Sample Code
+  ///
+  /// Querying [Window.platformBrightness]:
+  ///
+  /// ```dart
+  /// final Brightness brightness = WidgetsBinding.instance.window.platformBrightness;
+  /// ```
+  ///
+  /// Querying [MediaQuery] directly:
+  ///
+  /// ```dart
+  /// final Brightness brightness = MediaQuery.platformBrightnessOf(context);
+  /// ```
+  ///
+  /// Querying [MediaQueryData]:
+  ///
+  /// ```dart
+  /// final MediaQueryData mediaQueryData = MediaQuery.of(context);
+  /// final Brightness brightness = mediaQueryData.platformBrightness;
+  /// ```
+  ///
+  /// See [Window.onPlatformBrightnessChanged].
+  /// {@endtemplate}
+  @protected
+  void handlePlatformBrightnessChanged() { }
+
   /// Returns a [ViewConfiguration] configured for the [RenderView] based on the
   /// current environment.
   ///

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

@@ -1020,6 +1020,15 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
     });
   }
 
+  // RENDERING
+  @override
+  void didChangePlatformBrightness() {
+    setState(() {
+      // The platformBrightness property of window has changed. We reference
+      // window in our build function, so we need to call setState(), but
+      // we don't need to cache anything locally.
+    });
+  }
 
   // BUILDER
 

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

@@ -213,6 +213,9 @@ abstract class WidgetsBindingObserver {
   ///    boilerplate.
   void didChangeTextScaleFactor() { }
 
+  /// {@macro on_platform_brightness_change}
+  void didChangePlatformBrightness() { }
+
   /// Called when the system tells the app that the user's locale has
   /// changed. For example, if the user changes the system language
   /// settings.
@@ -408,6 +411,13 @@ mixin WidgetsBinding on BindingBase, SchedulerBinding, GestureBinding, RendererB
       observer.didChangeTextScaleFactor();
   }
 
+  @override
+  void handlePlatformBrightnessChanged() {
+    super.handlePlatformBrightnessChanged();
+    for (WidgetsBindingObserver observer in _observers)
+      observer.didChangePlatformBrightness();
+  }
+
   @override
   void handleAccessibilityFeaturesChanged() {
     super.handleAccessibilityFeaturesChanged();

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

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:ui' as ui;
+import 'dart:ui' show Brightness;
 
 import 'package:flutter/foundation.dart';
 
@@ -59,6 +60,7 @@ class MediaQueryData {
     this.size = Size.zero,
     this.devicePixelRatio = 1.0,
     this.textScaleFactor = 1.0,
+    this.platformBrightness = Brightness.light,
     this.padding = EdgeInsets.zero,
     this.viewInsets = EdgeInsets.zero,
     this.alwaysUse24HourFormat = false,
@@ -78,6 +80,7 @@ class MediaQueryData {
     : size = window.physicalSize / window.devicePixelRatio,
       devicePixelRatio = window.devicePixelRatio,
       textScaleFactor = window.textScaleFactor,
+      platformBrightness = window.platformBrightness,
       padding = EdgeInsets.fromWindowPadding(window.padding, window.devicePixelRatio),
       viewInsets = EdgeInsets.fromWindowPadding(window.viewInsets, window.devicePixelRatio),
       accessibleNavigation = window.accessibilityFeatures.accessibleNavigation,
@@ -110,6 +113,15 @@ class MediaQueryData {
   ///    textScaleFactor defined for a [BuildContext].
   final double textScaleFactor;
 
+  /// The current brightness mode of the host platform.
+  ///
+  /// For example, starting in Android Pie, battery saver mode asks all apps to
+  /// render in a "dark mode".
+  ///
+  /// Not all platforms necessarily support a concept of brightness mode. Those
+  /// platforms will report [Brightness.light] in this property.
+  final Brightness platformBrightness;
+
   /// The parts of the display that are completely obscured by system UI,
   /// typically by the device's keyboard.
   ///
@@ -204,6 +216,7 @@ class MediaQueryData {
     Size size,
     double devicePixelRatio,
     double textScaleFactor,
+    Brightness platformBrightness,
     EdgeInsets padding,
     EdgeInsets viewInsets,
     bool alwaysUse24HourFormat,
@@ -216,6 +229,7 @@ class MediaQueryData {
       size: size ?? this.size,
       devicePixelRatio: devicePixelRatio ?? this.devicePixelRatio,
       textScaleFactor: textScaleFactor ?? this.textScaleFactor,
+      platformBrightness: platformBrightness ?? this.platformBrightness,
       padding: padding ?? this.padding,
       viewInsets: viewInsets ?? this.viewInsets,
       alwaysUse24HourFormat: alwaysUse24HourFormat ?? this.alwaysUse24HourFormat,
@@ -252,6 +266,7 @@ class MediaQueryData {
       size: size,
       devicePixelRatio: devicePixelRatio,
       textScaleFactor: textScaleFactor,
+      platformBrightness: platformBrightness,
       padding: padding.copyWith(
         left: removeLeft ? 0.0 : null,
         top: removeTop ? 0.0 : null,
@@ -291,6 +306,7 @@ class MediaQueryData {
       size: size,
       devicePixelRatio: devicePixelRatio,
       textScaleFactor: textScaleFactor,
+      platformBrightness: platformBrightness,
       padding: padding,
       viewInsets: viewInsets.copyWith(
         left: removeLeft ? 0.0 : null,
@@ -314,6 +330,7 @@ class MediaQueryData {
     return typedOther.size == size
         && typedOther.devicePixelRatio == devicePixelRatio
         && typedOther.textScaleFactor == textScaleFactor
+        && typedOther.platformBrightness == platformBrightness
         && typedOther.padding == padding
         && typedOther.viewInsets == viewInsets
         && typedOther.alwaysUse24HourFormat == alwaysUse24HourFormat
@@ -329,6 +346,7 @@ class MediaQueryData {
       size,
       devicePixelRatio,
       textScaleFactor,
+      platformBrightness,
       padding,
       viewInsets,
       alwaysUse24HourFormat,
@@ -345,6 +363,7 @@ class MediaQueryData {
              'size: $size, '
              'devicePixelRatio: ${devicePixelRatio.toStringAsFixed(1)}, '
              'textScaleFactor: ${textScaleFactor.toStringAsFixed(1)}, '
+             'platformBrightness: $platformBrightness, '
              'padding: $padding, '
              'viewInsets: $viewInsets, '
              'alwaysUse24HourFormat: $alwaysUse24HourFormat, '
@@ -523,6 +542,15 @@ class MediaQuery extends InheritedWidget {
     return MediaQuery.of(context, nullOk: true)?.textScaleFactor ?? 1.0;
   }
 
+  /// Returns platformBrightness for the nearest MediaQuery ancestor or
+  /// [Brightness.light], if no such ancestor exists.
+  ///
+  /// Use of this method will cause the given [context] to rebuild any time that
+  /// any property of the ancestor [MediaQuery] changes.
+  static Brightness platformBrightnessOf(BuildContext context) {
+    return MediaQuery.of(context, nullOk: true)?.platformBrightness ?? Brightness.light;
+  }
+
   /// Returns the boldText accessibility setting for the nearest MediaQuery
   /// ancestor, or false if no such ancestor exists.
   static bool boldTextOverride(BuildContext context) {

packages/flutter/test/material/app_test.dart

@@ -435,4 +435,165 @@ void main() {
     // Default Cupertino US "select all" text.
     expect(find.text('Select All'), findsOneWidget);
   });
+
+  testWidgets('MaterialApp uses regular theme when platformBrightness is light', (WidgetTester tester) async {
+    // Mock the Window to explicitly report a light platformBrightness.
+    final TestWidgetsFlutterBinding binding = tester.binding;
+    binding.window.platformBrightnessTestValue = Brightness.light;
+
+    ThemeData appliedTheme;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          brightness: Brightness.light
+        ),
+        darkTheme: ThemeData(
+          brightness: Brightness.dark,
+        ),
+        home: Builder(
+          builder: (BuildContext context) {
+            appliedTheme = Theme.of(context);
+            return const SizedBox();
+          },
+        ),
+      ),
+    );
+
+    expect(appliedTheme.brightness, Brightness.light);
+  });
+
+  testWidgets('MaterialApp uses light theme when platformBrightness is dark but no dark theme is provided', (WidgetTester tester) async {
+    // Mock the Window to explicitly report a dark platformBrightness.
+    final TestWidgetsFlutterBinding binding = tester.binding;
+    binding.window.platformBrightnessTestValue = Brightness.dark;
+
+    ThemeData appliedTheme;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          brightness: Brightness.light
+        ),
+        home: Builder(
+          builder: (BuildContext context) {
+            appliedTheme = Theme.of(context);
+            return const SizedBox();
+          },
+        ),
+      ),
+    );
+
+    expect(appliedTheme.brightness, Brightness.light);
+  });
+
+  testWidgets('MaterialApp uses fallback light theme when platformBrightness is dark but no theme is provided at all', (WidgetTester tester) async {
+    // Mock the Window to explicitly report a dark platformBrightness.
+    final TestWidgetsFlutterBinding binding = tester.binding;
+    binding.window.platformBrightnessTestValue = Brightness.dark;
+
+    ThemeData appliedTheme;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Builder(
+          builder: (BuildContext context) {
+            appliedTheme = Theme.of(context);
+            return const SizedBox();
+          },
+        ),
+      ),
+    );
+
+    expect(appliedTheme.brightness, Brightness.light);
+  });
+
+  testWidgets('MaterialApp uses fallback light theme when platformBrightness is light and a dark theme is provided', (WidgetTester tester) async {
+    // Mock the Window to explicitly report a dark platformBrightness.
+    final TestWidgetsFlutterBinding binding = tester.binding;
+    binding.window.platformBrightnessTestValue = Brightness.light;
+
+    ThemeData appliedTheme;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        darkTheme: ThemeData(
+          brightness: Brightness.dark,
+        ),
+        home: Builder(
+          builder: (BuildContext context) {
+            appliedTheme = Theme.of(context);
+            return const SizedBox();
+          },
+        ),
+      ),
+    );
+
+    expect(appliedTheme.brightness, Brightness.light);
+  });
+
+  testWidgets('MaterialApp uses dark theme when platformBrightness is dark', (WidgetTester tester) async {
+    // Mock the Window to explicitly report a dark platformBrightness.
+    final TestWidgetsFlutterBinding binding = tester.binding;
+    binding.window.platformBrightnessTestValue = Brightness.dark;
+
+    ThemeData appliedTheme;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          brightness: Brightness.light
+        ),
+        darkTheme: ThemeData(
+          brightness: Brightness.dark,
+        ),
+        home: Builder(
+          builder: (BuildContext context) {
+            appliedTheme = Theme.of(context);
+            return const SizedBox();
+          },
+        ),
+      ),
+    );
+
+    expect(appliedTheme.brightness, Brightness.dark);
+  });
+
+  testWidgets('MaterialApp switches themes when the Window platformBrightness changes.', (WidgetTester tester) async {
+    // Mock the Window to explicitly report a light platformBrightness.
+    final TestWidgetsFlutterBinding binding = tester.binding;
+    binding.window.platformBrightnessTestValue = Brightness.light;
+
+    ThemeData themeBeforeBrightnessChange;
+    ThemeData themeAfterBrightnessChange;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: ThemeData(
+          brightness: Brightness.light
+        ),
+        darkTheme: ThemeData(
+          brightness: Brightness.dark,
+        ),
+        home: Builder(
+          builder: (BuildContext context) {
+            if (themeBeforeBrightnessChange == null) {
+              themeBeforeBrightnessChange = Theme.of(context);
+            } else {
+              themeAfterBrightnessChange = Theme.of(context);
+            }
+            return const SizedBox();
+          },
+        ),
+      ),
+    );
+
+    // Switch the platformBrightness from light to dark and pump the widget tree
+    // to process changes.
+    binding.window.platformBrightnessTestValue = Brightness.dark;
+    await tester.pumpAndSettle();
+
+    expect(themeBeforeBrightnessChange.brightness, Brightness.light);
+    expect(themeAfterBrightnessChange.brightness, Brightness.dark);
+  });
 }

packages/flutter/test/widgets/media_query_test.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:ui' show Brightness;
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
@@ -45,6 +46,7 @@ void main() {
     expect(data.invertColors, false);
     expect(data.disableAnimations, false);
     expect(data.boldText, false);
+    expect(data.platformBrightness, Brightness.light);
   });
 
   testWidgets('MediaQueryData.copyWith defaults to source', (WidgetTester tester) async {
@@ -60,6 +62,7 @@ void main() {
     expect(copied.invertColors, data.invertColors);
     expect(copied.disableAnimations, data.disableAnimations);
     expect(copied.boldText, data.boldText);
+    expect(copied.platformBrightness, data.platformBrightness);
   });
 
   testWidgets('MediaQuery.copyWith copies specified values', (WidgetTester tester) async {
@@ -75,6 +78,7 @@ void main() {
       invertColors: true,
       disableAnimations: true,
       boldText: true,
+      platformBrightness: Brightness.dark,
     );
     expect(copied.size, const Size(3.14, 2.72));
     expect(copied.devicePixelRatio, 1.41);
@@ -86,6 +90,7 @@ void main() {
     expect(copied.invertColors, true);
     expect(copied.disableAnimations, true);
     expect(copied.boldText, true);
+    expect(copied.platformBrightness, Brightness.dark);
   });
 
  testWidgets('MediaQuery.removePadding removes specified padding', (WidgetTester tester) async {
@@ -223,6 +228,33 @@ void main() {
    expect(insideTextScaleFactor, 4.0);
  });
 
+  testWidgets('MediaQuery.platformBrightnessOf', (WidgetTester tester) async {
+    Brightness outsideBrightness;
+    Brightness insideBrightness;
+
+    await tester.pumpWidget(
+      Builder(
+        builder: (BuildContext context) {
+          outsideBrightness = MediaQuery.platformBrightnessOf(context);
+          return MediaQuery(
+            data: const MediaQueryData(
+              platformBrightness: Brightness.dark,
+            ),
+            child: Builder(
+              builder: (BuildContext context) {
+                insideBrightness = MediaQuery.platformBrightnessOf(context);
+                return Container();
+              },
+            ),
+          );
+        },
+      ),
+    );
+
+    expect(outsideBrightness, Brightness.light);
+    expect(insideBrightness, Brightness.dark);
+  });
+
   testWidgets('MediaQuery.boldTextOverride', (WidgetTester tester) async {
     bool outsideBoldTextOverride;
     bool insideBoldTextOverride;

packages/flutter_test/lib/src/window.dart

@@ -59,10 +59,12 @@ class TestWindow implements Window {
   /// Hides the real device pixel ratio and reports the given [devicePixelRatio] instead.
   set devicePixelRatioTestValue(double devicePixelRatio) {
     _devicePixelRatio = devicePixelRatio;
+    onMetricsChanged();
   }
   /// Deletes any existing test device pixel ratio and returns to using the real device pixel ratio.
   void clearDevicePixelRatioTestValue() {
     _devicePixelRatio = null;
+    onMetricsChanged();
   }
 
   @override
@@ -71,10 +73,12 @@ class TestWindow implements Window {
   /// Hides the real physical size and reports the given [physicalSizeTestValue] instead.
   set physicalSizeTestValue (Size physicalSizeTestValue) {
     _physicalSizeTestValue = physicalSizeTestValue;
+    onMetricsChanged();
   }
   /// Deletes any existing test physical size and returns to using the real physical size.
   void clearPhysicalSizeTestValue() {
     _physicalSizeTestValue = null;
+    onMetricsChanged();
   }
 
   @override
@@ -83,10 +87,12 @@ class TestWindow implements Window {
   /// Hides the real view insets and reports the given [viewInsetsTestValue] instead.
   set viewInsetsTestValue(WindowPadding viewInsetsTestValue) {
     _viewInsetsTestValue = viewInsetsTestValue;
+    onMetricsChanged();
   }
   /// Deletes any existing test view insets and returns to using the real view insets.
   void clearViewInsetsTestValue() {
     _viewInsetsTestValue = null;
+    onMetricsChanged();
   }
 
   @override
@@ -95,10 +101,12 @@ class TestWindow implements Window {
   /// Hides the real padding and reports the given [paddingTestValue] instead.
   set paddingTestValue(WindowPadding paddingTestValue) {
     _paddingTestValue = paddingTestValue;
+    onMetricsChanged();
   }
   /// Deletes any existing test padding and returns to using the real padding.
   void clearPaddingTestValue() {
     _paddingTestValue = null;
+    onMetricsChanged();
   }
 
   @override
@@ -114,10 +122,12 @@ class TestWindow implements Window {
   /// Hides the real locale and reports the given [localeTestValue] instead.
   set localeTestValue(Locale localeTestValue) {
     _localeTestValue = localeTestValue;
+    onLocaleChanged();
   }
   /// Deletes any existing test locale and returns to using the real locale.
   void clearLocaleTestValue() {
     _localeTestValue = null;
+    onLocaleChanged();
   }
 
   @override
@@ -126,10 +136,12 @@ class TestWindow implements Window {
   /// Hides the real locales and reports the given [localesTestValue] instead.
   set localesTestValue(List<Locale> localesTestValue) {
     _localesTestValue = localesTestValue;
+    onLocaleChanged();
   }
   /// Deletes any existing test locales and returns to using the real locales.
   void clearLocalesTestValue() {
     _localesTestValue = null;
+    onLocaleChanged();
   }
 
   @override
@@ -145,10 +157,12 @@ class TestWindow implements Window {
   /// Hides the real text scale factor and reports the given [textScaleFactorTestValue] instead.
   set textScaleFactorTestValue(double textScaleFactorTestValue) {
     _textScaleFactorTestValue = textScaleFactorTestValue;
+    onTextScaleFactorChanged();
   }
   /// Deletes any existing test text scale factor and returns to using the real text scale factor.
   void clearTextScaleFactorTestValue() {
     _textScaleFactorTestValue = null;
+    onTextScaleFactorChanged();
   }
 
   @override
@@ -158,15 +172,17 @@ class TestWindow implements Window {
   VoidCallback get onPlatformBrightnessChanged => _window.onPlatformBrightnessChanged;
   @override
   set onPlatformBrightnessChanged(VoidCallback callback) {
-    _window.onPlatformBrightnessChanged =callback;
+    _window.onPlatformBrightnessChanged = callback;
   }
   /// Hides the real text scale factor and reports the given [platformBrightnessTestValue] instead.
   set platformBrightnessTestValue(Brightness platformBrightnessTestValue) {
     _platformBrightnessTestValue = platformBrightnessTestValue;
+    onPlatformBrightnessChanged();
   }
   /// Deletes any existing test platform brightness and returns to using the real platform brightness.
   void clearPlatformBrightnessTestValue() {
     _platformBrightnessTestValue = null;
+    onPlatformBrightnessChanged();
   }
 
   @override
@@ -237,10 +253,12 @@ class TestWindow implements Window {
   /// Hides the real semantics enabled and reports the given [semanticsEnabledTestValue] instead.
   set semanticsEnabledTestValue(bool semanticsEnabledTestValue) {
     _semanticsEnabledTestValue = semanticsEnabledTestValue;
+    onSemanticsEnabledChanged();
   }
   /// Deletes any existing test semantics enabled and returns to using the real semantics enabled.
   void clearSemanticsEnabledTestValue() {
     _semanticsEnabledTestValue = null;
+    onSemanticsEnabledChanged();
   }
 
   @override
@@ -263,10 +281,12 @@ class TestWindow implements Window {
   /// Hides the real accessibility features and reports the given [accessibilityFeaturesTestValue] instead.
   set accessibilityFeaturesTestValue(AccessibilityFeatures accessibilityFeaturesTestValue) {
     _accessibilityFeaturesTestValue = accessibilityFeaturesTestValue;
+    onAccessibilityFeaturesChanged();
   }
   /// Deletes any existing test accessibility features and returns to using the real accessibility features.
   void clearAccessibilityFeaturesTestValue() {
     _accessibilityFeaturesTestValue = null;
+    onAccessibilityFeaturesChanged();
   }
 
   @override

packages/flutter_test/test/window_test.dart

@@ -136,20 +136,6 @@ void main() {
     );
   });
 
-  testWidgets('TestWindow can fake semantics enabled', (WidgetTester tester) async {
-    verifyThatTestWindowCanFakeProperty<bool>(
-      tester: tester,
-      realValue: ui.window.semanticsEnabled,
-      fakeValue: !ui.window.semanticsEnabled,
-      propertyRetriever: () {
-        return WidgetsBinding.instance.window.semanticsEnabled;
-      },
-      propertyFaker: (TestWidgetsFlutterBinding binding, bool fakeValue) {
-        binding.window.semanticsEnabledTestValue = fakeValue;
-      }
-    );
-  });
-
   testWidgets('TestWindow can fake accessibility features', (WidgetTester tester) async {
     verifyThatTestWindowCanFakeProperty<AccessibilityFeatures>(
       tester: tester,