Add bottom to search bar (#68794)

dev/integration_tests/flutter_gallery/lib/demo/material/search_demo.dart

@@ -223,6 +223,12 @@ class _SearchDemoSearchDelegate extends SearchDelegate<int?> {
         ),
     ];
   }
+
+  @override
+  PreferredSizeWidget buildBottom(BuildContext context) => const PreferredSize(
+    preferredSize: Size.fromHeight(56.0),
+    child: Text('Numbers'),
+  );
 }
 
 class _ResultCard extends StatelessWidget {

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

@@ -69,8 +69,9 @@ Future<T?> showSearch<T>({
 ///
 /// The search page always shows an [AppBar] at the top where users can
 /// enter their search queries. The buttons shown before and after the search
-/// query text field can be customized via [SearchDelegate.buildLeading] and
-/// [SearchDelegate.buildActions].
+/// query text field can be customized via [SearchDelegate.buildLeading]
+/// and [SearchDelegate.buildActions]. Additonally, a widget can be placed
+/// across the bottom of the [AppBar] via [SearchDelegate.buildBottom].
 ///
 /// The body below the [AppBar] can either show suggested queries (returned by
 /// [SearchDelegate.buildSuggestions]) or - once the user submits a search  - the
@@ -113,6 +114,12 @@ abstract class SearchDelegate<T> {
   ///   @override
   ///   Widget buildLeading(BuildContext context) => Text("leading");
   ///
+  ///   PreferredSizeWidget buildBottom(BuildContext context) {
+  ///     return PreferredSize(
+  ///        preferredSize: Size.fromHeight(56.0),
+  ///        child: Text("bottom"));
+  ///   }
+  ///
   ///   @override
   ///   Widget buildSuggestions(BuildContext context) => Text("suggestions");
   ///
@@ -188,6 +195,16 @@ abstract class SearchDelegate<T> {
   ///  * [AppBar.actions], the intended use for the return value of this method.
   List<Widget> buildActions(BuildContext context);
 
+  /// Widget to display across the bottom of the [AppBar].
+  ///
+  /// Returns null by default, i.e. a bottom widget is not included.
+  ///
+  /// See also:
+  ///
+  ///  * [AppBar.bottom], the intended use for the return value of this method.
+  ///
+  PreferredSizeWidget? buildBottom(BuildContext context) => null;
+
   /// The theme used to configure the search page.
   ///
   /// The returned [ThemeData] will be used to wrap the entire search page,
@@ -560,12 +577,13 @@ class _SearchPageState<T> extends State<_SearchPage<T>> {
               decoration: InputDecoration(hintText: searchFieldLabel),
             ),
             actions: widget.delegate.buildActions(context),
+            bottom: widget.delegate.buildBottom(context),
           ),
           body: AnimatedSwitcher(
             duration: const Duration(milliseconds: 300),
             child: body,
           ),
-        ),
+        )
       ),
     );
   }

packages/flutter/test/material/search_test.dart

@@ -99,6 +99,7 @@ void main() {
     expect(find.text('HomeBody'), findsNothing);
     expect(find.text('HomeTitle'), findsNothing);
     expect(find.text('Suggestions'), findsOneWidget);
+    expect(find.text('Bottom'), findsOneWidget);
 
     // Simulate system back button
     final ByteData message = const JSONMethodCodec().encodeMethodCall(const MethodCall('popRoute'));
@@ -633,6 +634,11 @@ void main() {
                             textDirection: TextDirection.ltr,
                             textSelection: const TextSelection(baseOffset: 0, extentOffset: 0),
                           ),
+                          TestSemantics(
+                            id: 14,
+                            label: 'Bottom',
+                            textDirection: TextDirection.ltr,
+                          ),
                         ],
                       ),
                       TestSemantics(
@@ -893,4 +899,12 @@ class _TestSearchDelegate extends SearchDelegate<String> {
   List<Widget> buildActions(BuildContext context) {
     return actions;
   }
+
+  @override
+  PreferredSizeWidget buildBottom(BuildContext context) {
+    return const PreferredSize(
+      preferredSize: Size.fromHeight(56.0),
+      child: Text('Bottom'),
+    );
+  }
 }