[material_3_demo] Use switch expressions (#2193)

material_3_demo/lib/color_palettes_screen.dart

@@ -357,15 +357,11 @@ class ColorChip extends StatelessWidget {
   final Color? onColor;
   final String label;
 
-  static Color contrastColor(Color color) {
+  static Color contrastColor(Color color) =>
-    final brightness = ThemeData.estimateBrightnessForColor(color);
+      switch (ThemeData.estimateBrightnessForColor(color)) {
-    switch (brightness) {
+        Brightness.dark => Colors.white,
-      case Brightness.dark:
+        Brightness.light => Colors.black
-        return Colors.white;
+      };
-      case Brightness.light:
-        return Colors.black;
-    }
-  }
 
   @override
   Widget build(BuildContext context) {

material_3_demo/lib/home.dart

@@ -108,10 +108,11 @@ class _HomeState extends State<Home> with SingleTickerProviderStateMixin {
   }
 
   Widget createScreenFor(
-      ScreenSelected screenSelected, bool showNavBarExample) {
+    ScreenSelected screenSelected,
+    bool showNavBarExample,
+  ) =>
       switch (screenSelected) {
-      case ScreenSelected.component:
+        ScreenSelected.component => Expanded(
-        return Expanded(
             child: OneTwoTransition(
               animation: railAnimation,
               one: FirstComponentList(
@@ -122,15 +123,11 @@ class _HomeState extends State<Home> with SingleTickerProviderStateMixin {
                 scaffoldKey: scaffoldKey,
               ),
             ),
-        );
+          ),
-      case ScreenSelected.color:
+        ScreenSelected.color => const ColorPalettesScreen(),
-        return const ColorPalettesScreen();
+        ScreenSelected.typography => const TypographyScreen(),
-      case ScreenSelected.typography:
+        ScreenSelected.elevation => const ElevationScreen()
-        return const TypographyScreen();
+      };
-      case ScreenSelected.elevation:
-        return const ElevationScreen();
-    }
-  }
 
   PreferredSizeWidget createAppBar() {
     return AppBar(

material_3_demo/lib/main.dart

@@ -47,17 +47,13 @@ class _AppState extends State<App> {
   ColorScheme? imageColorScheme = const ColorScheme.light();
   ColorSelectionMethod colorSelectionMethod = ColorSelectionMethod.colorSeed;
 
-  bool get useLightMode {
+  bool get useLightMode => switch (themeMode) {
-    switch (themeMode) {
+        ThemeMode.system =>
-      case ThemeMode.system:
+          View.of(context).platformDispatcher.platformBrightness ==
-        return View.of(context).platformDispatcher.platformBrightness ==
+              Brightness.light,
-            Brightness.light;
+        ThemeMode.light => true,
-      case ThemeMode.light:
+        ThemeMode.dark => false
-        return true;
+      };
-      case ThemeMode.dark:
-        return false;
-    }
-  }
 
   void handleBrightnessChange(bool useLightMode) {
     setState(() {