Extend SystemUiOverlayStyle with additonal values for each platform (#17171)

packages/flutter/lib/src/cupertino/nav_bar.dart

@@ -294,9 +294,18 @@ Widget _wrapWithBackground({
   );
 
   final bool darkBackground = backgroundColor.computeLuminance() < 0.179;
-  SystemChrome.setSystemUIOverlayStyle(
-    darkBackground ? SystemUiOverlayStyle.light : SystemUiOverlayStyle.dark
-  );
+  // TODO(jonahwilliams): remove once we have platform themes.
+  switch (defaultTargetPlatform) {
+    case TargetPlatform.iOS:
+      SystemChrome.setSystemUIOverlayStyle(
+        darkBackground ? SystemUiOverlayStyle.light : SystemUiOverlayStyle.dark
+      );
+      break;
+    case TargetPlatform.android:
+    case TargetPlatform.fuchsia:
+      SystemChrome.setSystemUIOverlayStyle(SystemUiOverlayStyle.dark);
+  }
+
 
   if (backgroundColor.alpha == 0xFF)
     return childWithBackground;

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

@@ -346,9 +346,17 @@ class _AppBarState extends State<AppBar> {
     TextStyle sideStyle = widget.textTheme?.body1 ?? themeData.primaryTextTheme.body1;
 
     final Brightness brightness = widget.brightness ?? themeData.primaryColorBrightness;
-    SystemChrome.setSystemUIOverlayStyle(brightness == Brightness.dark
-      ? SystemUiOverlayStyle.light
-      : SystemUiOverlayStyle.dark);
+    // TODO(jonahwilliams): remove once we have platform themes.
+    switch (defaultTargetPlatform) {
+      case TargetPlatform.iOS:
+        SystemChrome.setSystemUIOverlayStyle(brightness == Brightness.dark
+          ? SystemUiOverlayStyle.light
+          : SystemUiOverlayStyle.dark);
+        break;
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+        SystemChrome.setSystemUIOverlayStyle(SystemUiOverlayStyle.dark);
+    }
 
     if (widget.toolbarOpacity != 1.0) {
       final double opacity = const Interval(0.25, 1.0, curve: Curves.fastOutSlowIn).transform(widget.toolbarOpacity);

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

@@ -5,6 +5,7 @@
 import 'dart:ui' show Color, hashValues;
 
 import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
 import 'button_theme.dart';
@@ -16,20 +17,7 @@ import 'input_decorator.dart';
 import 'slider_theme.dart';
 import 'typography.dart';
 
-/// Describes the contrast needs of a color.
-enum Brightness {
-  /// The color is dark and will require a light text color to achieve readable
-  /// contrast.
-  ///
-  /// For example, the color might be dark grey, requiring white text.
-  dark,
-
-  /// The color is light and will require a dark text color to achieve readable
-  /// contrast.
-  ///
-  /// For example, the color might be bright white, requiring black text.
-  light,
-}
+export 'package:flutter/services.dart' show Brightness;
 
 // Deriving these values is black magic. The spec claims that pressed buttons
 // have a highlight of 0x66999999, but that's clearly wrong. The videos in the

packages/flutter/lib/src/services/system_chrome.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:ui';
 
 import 'package:flutter/foundation.dart';
 
@@ -77,17 +78,142 @@ enum SystemUiOverlay {
   bottom,
 }
 
+/// Describes the contrast needs of a color.
+enum Brightness {
+  /// The color is dark and will require a light text color to achieve readable
+  /// contrast.
+  ///
+  /// For example, the color might be dark grey, requiring white text.
+  dark,
+
+  /// The color is light and will require a dark text color to achieve readable
+  /// contrast.
+  ///
+  /// For example, the color might be bright white, requiring black text.
+  light,
+}
+
 /// Specifies a preference for the style of the system overlays.
 ///
 /// Used by [SystemChrome.setSystemUIOverlayStyle].
-enum SystemUiOverlayStyle {
+class SystemUiOverlayStyle {
   /// System overlays should be drawn with a light color. Intended for
   /// applications with a dark background.
-  light,
+  static const SystemUiOverlayStyle light = const SystemUiOverlayStyle(
+    systemNavigationBarColor: const Color(0xFFFFFFFF),
+    systemNavigationBarDividerColor: null,
+    statusBarColor: null,
+    systemNavigationBarIconBrightness: Brightness.dark,
+    statusBarIconBrightness: Brightness.dark,
+    statusBarBrightness: Brightness.dark,
+  );
 
   /// System overlays should be drawn with a dark color. Intended for
   /// applications with a light background.
-  dark,
+  static const SystemUiOverlayStyle dark = const SystemUiOverlayStyle(
+    systemNavigationBarColor: const Color(0xFF000000),
+    systemNavigationBarDividerColor: null,
+    statusBarColor: null,
+    systemNavigationBarIconBrightness: Brightness.light,
+    statusBarIconBrightness: Brightness.light,
+    statusBarBrightness: Brightness.light,
+  );
+
+  /// Creates a new [SystemUiOverlayStyle].
+  const SystemUiOverlayStyle({
+    this.systemNavigationBarColor,
+    this.systemNavigationBarDividerColor,
+    this.systemNavigationBarIconBrightness,
+    this.statusBarColor,
+    this.statusBarBrightness,
+    this.statusBarIconBrightness,
+  });
+
+  /// The color of the system bottom navigation bar.
+  /// 
+  /// Only honored in Android versions O and greater.
+  final Color systemNavigationBarColor;
+
+  /// The color of the divider between the system's bottom navigation bar and the app's content.
+  /// 
+  /// Only honored in Android versions P and greater.
+  final Color systemNavigationBarDividerColor;
+
+  /// The brightness of the system navigation bar icons.
+  /// 
+  /// Only honored in Android versions O and greater.
+  final Brightness systemNavigationBarIconBrightness;
+
+  /// The color of top status bar.
+  /// 
+  /// Only honored in Android version M and greater.
+  final Color statusBarColor;
+
+  /// The brightness of top status bar.
+  /// 
+  /// Only honored in iOS .
+  final Brightness statusBarBrightness;
+
+  /// The brightness of the top status bar icons.
+  /// 
+  /// Only honored in Android version M and greater.
+  final Brightness statusBarIconBrightness;
+
+  /// Convert this event to a map for serialization.
+  Map<String, dynamic> _toMap() {
+    return <String, dynamic>{
+      'systemNavigationBarColor': systemNavigationBarColor?.value,
+      'systemNavigationBarDividerColor': systemNavigationBarDividerColor?.value,
+      'statusBarColor': statusBarColor?.value,
+      'statusBarBrightness': statusBarBrightness?.toString(),
+      'statusBarIconBrightness': statusBarIconBrightness?.toString(),
+      'systemNavigationBarIconBrightness': systemNavigationBarIconBrightness?.toString(),
+    };
+  }
+
+  /// Creates a copy of this theme with the given fields replaced with new values.
+  SystemUiOverlayStyle copyWith({
+    Color systemNavigationBarColor,
+    Color systemNavigationBarDividerColor,
+    Color statusBarColor,
+    Brightness statusBarBrightness,
+    Brightness statusBarIconBrightness,
+    Brightness systemNavigationBarIconBrightness,
+  }) {
+    return new SystemUiOverlayStyle(
+      systemNavigationBarColor: systemNavigationBarColor ?? this.systemNavigationBarColor,
+      systemNavigationBarDividerColor: systemNavigationBarDividerColor ?? this.systemNavigationBarDividerColor,
+      statusBarColor: statusBarColor ?? this.statusBarColor,
+      statusBarIconBrightness: statusBarIconBrightness ?? this.statusBarIconBrightness,
+      statusBarBrightness: statusBarBrightness ?? this.statusBarBrightness,
+      systemNavigationBarIconBrightness: systemNavigationBarIconBrightness ?? this.systemNavigationBarIconBrightness,
+    );
+  }
+
+  @override
+  int get hashCode {
+    return hashValues(
+      systemNavigationBarColor,
+      systemNavigationBarDividerColor,
+      statusBarColor,
+      statusBarBrightness,
+      statusBarIconBrightness,
+      systemNavigationBarIconBrightness,
+    );
+  }
+
+  @override
+  bool operator ==(dynamic other) {
+    if (other.runtimeType != runtimeType)
+      return false;
+    final SystemUiOverlayStyle typedOther = other;
+    return typedOther.systemNavigationBarColor == systemNavigationBarColor
+      && typedOther.systemNavigationBarDividerColor == systemNavigationBarDividerColor
+      && typedOther.statusBarColor == statusBarColor
+      && typedOther.statusBarIconBrightness == statusBarIconBrightness
+      && typedOther.statusBarBrightness == statusBarBrightness
+      && typedOther.systemNavigationBarIconBrightness == systemNavigationBarIconBrightness;
+  }
 }
 
 List<String> _stringify(List<dynamic> list) {
@@ -193,14 +319,9 @@ class SystemChrome {
     scheduleMicrotask(() {
       assert(_pendingStyle != null);
       if (_pendingStyle != _latestStyle) {
-        // TODO(jonahwilliams): remove when rolling chrome change.
         SystemChannels.platform.invokeMethod(
           'SystemChrome.setSystemUIOverlayStyle',
-          <String, dynamic>{
-            'statusBarBrightness': _pendingStyle == SystemUiOverlayStyle.light 
-              ? 'Brightness.light'
-              : 'Brightness.dark',
-          }
+          _pendingStyle._toMap(),
         );
         _latestStyle = _pendingStyle;
       }