Added support for AppBarTheme.toolbarHeight (#80467)

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

@@ -54,6 +54,14 @@ class _ToolbarContainerLayout extends SingleChildLayoutDelegate {
       toolbarHeight != oldDelegate.toolbarHeight;
 }
 
+class _PreferredAppBarSize extends Size {
+  _PreferredAppBarSize(this.toolbarHeight, this.bottomHeight)
+    : super.fromHeight((toolbarHeight ?? kToolbarHeight) + (bottomHeight ?? 0));
+
+  final double? toolbarHeight;
+  final double? bottomHeight;
+}
+
 /// A material design app bar.
 ///
 /// An app bar consists of a toolbar and potentially other widgets, such as a
@@ -202,9 +210,21 @@ class AppBar extends StatefulWidget implements PreferredSizeWidget {
        assert(primary != null),
        assert(toolbarOpacity != null),
        assert(bottomOpacity != null),
-       preferredSize = Size.fromHeight(toolbarHeight ?? kToolbarHeight + (bottom?.preferredSize.height ?? 0.0)),
+       preferredSize = _PreferredAppBarSize(toolbarHeight, bottom?.preferredSize.height),
        super(key: key);
 
+  /// Used by [Scaffold] to compute its [AppBar]'s overall height. The returned value is
+  /// the same `preferredSize.height` unless [AppBar.toolbarHeight] was null and
+  /// `AppBarTheme.of(context).toolbarHeight` is non-null. In that case the
+  /// return value is the sum of the theme's toolbar height and the height of
+  /// the app bar's [AppBar.bottom] widget.
+  static double preferredHeightFor(BuildContext context, Size preferredSize) {
+    if (preferredSize is _PreferredAppBarSize && preferredSize.toolbarHeight == null) {
+      return (AppBarTheme.of(context).toolbarHeight ?? kToolbarHeight) + (preferredSize.bottomHeight ?? 0);
+    }
+    return preferredSize.height;
+  }
+
   /// {@template flutter.material.appbar.leading}
   /// A widget to display before the toolbar's [title].
   ///
@@ -781,7 +801,7 @@ class _AppBarState extends State<AppBar> {
     final bool canPop = parentRoute?.canPop ?? false;
     final bool useCloseButton = parentRoute is PageRoute<dynamic> && parentRoute.fullscreenDialog;
 
-    final double toolbarHeight = widget.toolbarHeight ?? kToolbarHeight;
+    final double toolbarHeight = widget.toolbarHeight ?? appBarTheme.toolbarHeight ?? kToolbarHeight;
     final bool backwardsCompatibility = widget.backwardsCompatibility ?? appBarTheme.backwardsCompatibility ?? true;
 
     final Color backgroundColor = backwardsCompatibility

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

@@ -39,6 +39,7 @@ class AppBarTheme with Diagnosticable {
     this.textTheme,
     this.centerTitle,
     this.titleSpacing,
+    this.toolbarHeight,
     this.toolbarTextStyle,
     this.titleTextStyle,
     this.systemOverlayStyle,
@@ -144,6 +145,15 @@ class AppBarTheme with Diagnosticable {
   /// If null, [AppBar] uses default value of [NavigationToolbar.kMiddleSpacing].
   final double? titleSpacing;
 
+  /// Overrides the default value for the [AppBar.toolbarHeight]
+  /// property in all descendant [AppBar] widgets.
+  ///
+  /// See also:
+  ///
+  ///  * [AppBar.preferredHeightFor], which computes the overall
+  ///    height of an AppBar widget, taking this value into account.
+  final double? toolbarHeight;
+
   /// Overrides the default value for the obsolete [AppBar.toolbarTextStyle]
   /// property in all descendant [AppBar] widgets.
   ///
@@ -184,6 +194,7 @@ class AppBarTheme with Diagnosticable {
     TextTheme? textTheme,
     bool? centerTitle,
     double? titleSpacing,
+    double? toolbarHeight,
     TextStyle? toolbarTextStyle,
     TextStyle? titleTextStyle,
     SystemUiOverlayStyle? systemOverlayStyle,
@@ -204,6 +215,7 @@ class AppBarTheme with Diagnosticable {
       textTheme: textTheme ?? this.textTheme,
       centerTitle: centerTitle ?? this.centerTitle,
       titleSpacing: titleSpacing ?? this.titleSpacing,
+      toolbarHeight: toolbarHeight ?? this.toolbarHeight,
       toolbarTextStyle: toolbarTextStyle ?? this.toolbarTextStyle,
       titleTextStyle: titleTextStyle ?? this.titleTextStyle,
       systemOverlayStyle: systemOverlayStyle ?? this.systemOverlayStyle,
@@ -234,6 +246,7 @@ class AppBarTheme with Diagnosticable {
       textTheme: TextTheme.lerp(a?.textTheme, b?.textTheme, t),
       centerTitle: t < 0.5 ? a?.centerTitle : b?.centerTitle,
       titleSpacing: lerpDouble(a?.titleSpacing, b?.titleSpacing, t),
+      toolbarHeight: lerpDouble(a?.toolbarHeight, b?.toolbarHeight, t),
       toolbarTextStyle: TextStyle.lerp(a?.toolbarTextStyle, b?.toolbarTextStyle, t),
       titleTextStyle: TextStyle.lerp(a?.titleTextStyle, b?.titleTextStyle, t),
       systemOverlayStyle: t < 0.5 ? a?.systemOverlayStyle : b?.systemOverlayStyle,
@@ -254,6 +267,7 @@ class AppBarTheme with Diagnosticable {
       textTheme,
       centerTitle,
       titleSpacing,
+      toolbarHeight,
       toolbarTextStyle,
       titleTextStyle,
       systemOverlayStyle,
@@ -278,6 +292,7 @@ class AppBarTheme with Diagnosticable {
         && other.textTheme == textTheme
         && other.centerTitle == centerTitle
         && other.titleSpacing == titleSpacing
+        && other.toolbarHeight == toolbarHeight
         && other.toolbarTextStyle == toolbarTextStyle
         && other.titleTextStyle == titleTextStyle
         && other.systemOverlayStyle == systemOverlayStyle
@@ -297,6 +312,7 @@ class AppBarTheme with Diagnosticable {
     properties.add(DiagnosticsProperty<TextTheme>('textTheme', textTheme, defaultValue: null));
     properties.add(DiagnosticsProperty<bool>('centerTitle', centerTitle, defaultValue: null));
     properties.add(DiagnosticsProperty<double>('titleSpacing', titleSpacing, defaultValue: null));
+    properties.add(DiagnosticsProperty<double>('toolbarHeight', toolbarHeight, defaultValue: null));
     properties.add(DiagnosticsProperty<TextStyle>('toolbarTextStyle', toolbarTextStyle, defaultValue: null));
     properties.add(DiagnosticsProperty<TextStyle>('titleTextStyle', titleTextStyle, defaultValue: null));
     properties.add(DiagnosticsProperty<bool>('backwardsCompatibility', backwardsCompatibility, defaultValue: null));

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

@@ -3035,7 +3035,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin, Resto
 
     if (widget.appBar != null) {
       final double topPadding = widget.primary ? mediaQuery.padding.top : 0.0;
-      _appBarMaxHeight = widget.appBar!.preferredSize.height + topPadding;
+      _appBarMaxHeight = AppBar.preferredHeightFor(context, widget.appBar!.preferredSize) + topPadding;
       assert(_appBarMaxHeight! >= 0.0 && _appBarMaxHeight!.isFinite);
       _addIfNonNull(
         children,

packages/flutter/test/material/app_bar_test.dart

@@ -2822,4 +2822,57 @@ void main() {
 
     expect(tester.takeException(), isNull);
   });
+
+  testWidgets('AppBar.preferredHeightFor', (WidgetTester tester) async {
+    late double preferredHeight;
+    late Size preferredSize;
+
+    Widget buildFrame({ double? themeToolbarHeight, double? appBarToolbarHeight }) {
+      final AppBar appBar = AppBar(
+        toolbarHeight: appBarToolbarHeight,
+      );
+      return MaterialApp(
+        theme: ThemeData.light().copyWith(
+          appBarTheme: AppBarTheme(
+            toolbarHeight: themeToolbarHeight,
+          ),
+        ),
+        home: Builder(
+          builder: (BuildContext context) {
+            preferredHeight = AppBar.preferredHeightFor(context, appBar.preferredSize);
+            preferredSize = appBar.preferredSize;
+            return Scaffold(
+              appBar: appBar,
+              body: const Placeholder(),
+            );
+          },
+        ),
+      );
+    }
+
+    await tester.pumpWidget(buildFrame());
+    expect(tester.getSize(find.byType(AppBar)).height, kToolbarHeight);
+    expect(preferredHeight, kToolbarHeight);
+    expect(preferredSize.height, kToolbarHeight);
+
+    await tester.pumpWidget(buildFrame(themeToolbarHeight: 96));
+    await tester.pumpAndSettle(); // Animate MaterialApp theme change.
+    expect(tester.getSize(find.byType(AppBar)).height, 96);
+    expect(preferredHeight, 96);
+    // Special case: AppBarTheme.toolbarHeight specified,
+    // AppBar.theme.toolbarHeight is null.
+    expect(preferredSize.height, kToolbarHeight);
+
+    await tester.pumpWidget(buildFrame(appBarToolbarHeight: 64));
+    await tester.pumpAndSettle(); // Animate MaterialApp theme change.
+    expect(tester.getSize(find.byType(AppBar)).height, 64);
+    expect(preferredHeight, 64);
+    expect(preferredSize.height, 64);
+
+    await tester.pumpWidget(buildFrame(appBarToolbarHeight: 64, themeToolbarHeight: 96));
+    await tester.pumpAndSettle(); // Animate MaterialApp theme change.
+    expect(tester.getSize(find.byType(AppBar)).height, 64);
+    expect(preferredHeight, 64);
+    expect(preferredSize.height, 64);
+  });
 }

packages/flutter/test/material/app_bar_theme_test.dart

@@ -15,14 +15,18 @@ void main() {
   });
 
   testWidgets('Passing no AppBarTheme returns defaults', (WidgetTester tester) async {
-    await tester.pumpWidget(MaterialApp(
-      home: Scaffold(appBar: AppBar(
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          appBar: AppBar(
             backwardsCompatibility: false,
             actions: <Widget>[
               IconButton(icon: const Icon(Icons.share), onPressed: () { }),
             ],
-      )),
-    ));
+          ),
+        ),
+      ),
+    );
 
     final Material widget = _getAppBarMaterial(tester);
     final IconTheme iconTheme = _getAppBarIconTheme(tester);
@@ -38,21 +42,27 @@ void main() {
     expect(actionsIconTheme.data, const IconThemeData(color: Colors.white));
     expect(actionIconText.text.style!.color, Colors.white);
     expect(text.style, Typography.material2014().englishLike.bodyText2!.merge(Typography.material2014().white.bodyText2));
+    expect(tester.getSize(find.byType(AppBar)).height, kToolbarHeight);
+    expect(tester.getSize(find.byType(AppBar)).width, 800);
   });
 
   testWidgets('AppBar uses values from AppBarTheme', (WidgetTester tester) async {
     final AppBarTheme appBarTheme = _appBarTheme();
 
-    await tester.pumpWidget(MaterialApp(
+    await tester.pumpWidget(
+      MaterialApp(
         theme: ThemeData(appBarTheme: appBarTheme),
-      home: Scaffold(appBar: AppBar(
+        home: Scaffold(
+          appBar: AppBar(
             backwardsCompatibility: false,
             title: const Text('App Bar Title'),
             actions: <Widget>[
               IconButton(icon: const Icon(Icons.share), onPressed: () { }),
             ],
-      )),
-    ));
+          ),
+        ),
+      ),
+    );
 
     final Material widget = _getAppBarMaterial(tester);
     final IconTheme iconTheme = _getAppBarIconTheme(tester);
@@ -68,6 +78,8 @@ void main() {
     expect(actionsIconTheme.data, appBarTheme.actionsIconTheme);
     expect(actionIconText.text.style!.color, appBarTheme.actionsIconTheme!.color);
     expect(text.style, appBarTheme.toolbarTextStyle);
+    expect(tester.getSize(find.byType(AppBar)).height, appBarTheme.toolbarHeight);
+    expect(tester.getSize(find.byType(AppBar)).width, 800);
   });
 
   testWidgets('SliverAppBar allows AppBar to determine backwardsCompatibility', (WidgetTester tester) async {
@@ -531,6 +543,7 @@ AppBarTheme _appBarTheme() {
     elevation: elevation,
     shadowColor: shadowColor,
     iconTheme: iconThemeData,
+    toolbarHeight: 96,
     toolbarTextStyle: TextStyle(color: Colors.yellow),
     titleTextStyle: TextStyle(color: Colors.pink),
   );