Added ExpansionTileController (#123298)

Added ExpansionTileController

Author: HansMuller

examples/api/lib/material/expansion_tile/expansion_tile.1.dart

@@ -0,0 +1,84 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flutter code sample for [ExpansionTile] and [ExpansionTileController]
+
+import 'package:flutter/material.dart';
+
+void main() {
+  runApp(const ExpansionTileControllerApp());
+}
+
+class ExpansionTileControllerApp extends StatefulWidget {
+  const ExpansionTileControllerApp({ super.key });
+
+  @override
+  State<ExpansionTileControllerApp> createState() => _ExpansionTileControllerAppState();
+}
+
+class _ExpansionTileControllerAppState extends State<ExpansionTileControllerApp> {
+  final ExpansionTileController controller = ExpansionTileController();
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: 'Flutter Code Sample for ExpansionTileController.',
+      theme: ThemeData(useMaterial3: true),
+      home: Scaffold(
+        appBar: AppBar(title: const Text('ExpansionTileController Example')),
+        body: Column(
+          children: <Widget>[
+            // A controller has been provided to the ExpansionTile because it's
+            // going to be accessed from a component that is not within the
+            // tile's BuildContext.
+            ExpansionTile(
+              controller: controller,
+              title: const Text('ExpansionTile with explicit controller.'),
+              children: <Widget>[
+                Container(
+                  alignment: Alignment.center,
+                  padding: const EdgeInsets.all(24),
+                  child: const Text('ExpansionTile Contents'),
+                ),
+              ],
+            ),
+            const SizedBox(height: 8),
+            ElevatedButton(
+              child: const Text('Expand/Collapse the Tile Above'),
+              onPressed: () {
+                if (controller.isExpanded) {
+                  controller.collapse();
+                } else {
+                  controller.expand();
+                }
+              },
+            ),
+            const SizedBox(height: 48),
+            // A controller has not been provided to the ExpansionTile because
+            // the automatically created one can be retrieved via the tile's BuildContext.
+            ExpansionTile(
+              title: const Text('ExpansionTile with implicit controller.'),
+              children: <Widget>[
+                Builder(
+                  builder: (BuildContext context) {
+                    return Container(
+                      padding: const EdgeInsets.all(24),
+                      alignment: Alignment.center,
+                      child: ElevatedButton(
+                        child: const Text('Collapse This Tile'),
+                        onPressed: () {
+                          return ExpansionTileController.of(context).collapse();
+                        },
+                      ),
+                    );
+                  },
+                ),
+              ],
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}

examples/api/test/material/expansion_tile/expansion_tile.1_test.dart

@@ -0,0 +1,31 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_api_samples/material/expansion_tile/expansion_tile.1.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Test the basics of ExpansionTileControllerApp', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.ExpansionTileControllerApp(),
+    );
+
+    expect(find.text('ExpansionTile Contents'), findsNothing);
+    expect(find.text('Collapse This Tile'), findsNothing);
+
+    await tester.tap(find.text('Expand/Collapse the Tile Above'));
+    await tester.pumpAndSettle();
+    expect(find.text('ExpansionTile Contents'), findsOneWidget);
+    await tester.tap(find.text('Expand/Collapse the Tile Above'));
+    await tester.pumpAndSettle();
+    expect(find.text('ExpansionTile Contents'), findsNothing);
+
+    await tester.tap(find.text('ExpansionTile with implicit controller.'));
+    await tester.pumpAndSettle();
+    expect(find.text('Collapse This Tile'), findsOneWidget);
+    await tester.tap(find.text('Collapse This Tile'));
+    await tester.pumpAndSettle();
+    expect(find.text('Collapse This Tile'), findsNothing);
+  });
+}