Add CupertinoTabBar.height (#72919)

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

@@ -65,6 +65,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
     this.activeColor,
     this.inactiveColor = _kDefaultTabBarInactiveColor,
     this.iconSize = 30.0,
+    this.height = _kTabBarHeight,
     this.border = const Border(
       top: BorderSide(
         color: _kDefaultTabBarBorderColor,
@@ -79,6 +80,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
        assert(currentIndex != null),
        assert(0 <= currentIndex && currentIndex < items.length),
        assert(iconSize != null),
+       assert(height != null && height >= 0.0),
        assert(inactiveColor != null),
        super(key: key);
 
@@ -129,13 +131,18 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
   /// Must not be null.
   final double iconSize;
 
+  /// The height of the [CupertinoTabBar].
+  ///
+  /// Defaults to 50.0. Must not be null.
+  final double height;
+
   /// The border of the [CupertinoTabBar].
   ///
   /// The default value is a one physical pixel top border with grey color.
   final Border? border;
 
   @override
-  Size get preferredSize => const Size.fromHeight(_kTabBarHeight);
+  Size get preferredSize => Size.fromHeight(height);
 
   /// Indicates whether the tab bar is fully opaque or can have contents behind
   /// it show through it.
@@ -178,7 +185,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
         color: backgroundColor,
       ),
       child: SizedBox(
-        height: _kTabBarHeight + bottomPadding,
+        height: height + bottomPadding,
         child: IconTheme.merge( // Default with the inactive state.
           data: IconThemeData(color: inactive, size: iconSize),
           child: DefaultTextStyle( // Default with the inactive state.
@@ -285,6 +292,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
     Color? activeColor,
     Color? inactiveColor,
     double? iconSize,
+    double? height,
     Border? border,
     int? currentIndex,
     ValueChanged<int>? onTap,
@@ -296,6 +304,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
       activeColor: activeColor ?? this.activeColor,
       inactiveColor: inactiveColor ?? this.inactiveColor,
       iconSize: iconSize ?? this.iconSize,
+      height: height ?? this.height,
       border: border ?? this.border,
       currentIndex: currentIndex ?? this.currentIndex,
       onTap: onTap ?? this.onTap,

packages/flutter/test/cupertino/bottom_tab_bar_test.dart

@@ -327,6 +327,49 @@ Future<void> main() async {
     expect(tester.getSize(find.byType(CupertinoTabBar)).height, 90.0);
   });
 
+  testWidgets('Set custom height', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/51704
+    const double tabBarHeight = 56.0;
+    final CupertinoTabBar tabBar = CupertinoTabBar(
+      height: tabBarHeight,
+      items: <BottomNavigationBarItem>[
+        BottomNavigationBarItem(
+          icon: ImageIcon(MemoryImage(Uint8List.fromList(kTransparentImage))),
+          label: 'Aka',
+        ),
+        BottomNavigationBarItem(
+          icon: ImageIcon(MemoryImage(Uint8List.fromList(kTransparentImage))),
+          label: 'Shiro',
+        ),
+      ],
+    );
+
+    // Verify height with no bottom padding.
+    await pumpWidgetWithBoilerplate(tester, MediaQuery(
+      data: const MediaQueryData(),
+      child: CupertinoTabScaffold(
+        tabBar: tabBar,
+        tabBuilder: (BuildContext context, int index) {
+          return const Placeholder();
+        },
+      ),
+    ));
+    expect(tester.getSize(find.byType(CupertinoTabBar)).height, tabBarHeight);
+
+    // Verify height with bottom padding.
+    const double bottomPadding = 40.0;
+    await pumpWidgetWithBoilerplate(tester, MediaQuery(
+      data: const MediaQueryData(padding: EdgeInsets.only(bottom: bottomPadding)),
+      child: CupertinoTabScaffold(
+        tabBar: tabBar,
+        tabBuilder: (BuildContext context, int index) {
+          return const Placeholder();
+        },
+      ),
+    ));
+    expect(tester.getSize(find.byType(CupertinoTabBar)).height, tabBarHeight + bottomPadding);
+  });
+
   testWidgets('Opaque background does not add blur effects', (WidgetTester tester) async {
     await pumpWidgetWithBoilerplate(tester, MediaQuery(
       data: const MediaQueryData(),