[Gallery] Fix directory structure (#312)

gallery/lib/demos/material/bottom_sheet_demo.dart

@@ -0,0 +1,192 @@
+// Copyright 2019 The Flutter team. 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/material.dart';
+
+import 'package:gallery/l10n/gallery_localizations.dart';
+
+enum BottomSheetDemoType {
+  persistent,
+  modal,
+}
+
+class BottomSheetDemo extends StatelessWidget {
+  BottomSheetDemo({Key key, @required this.type}) : super(key: key);
+
+  final BottomSheetDemoType type;
+
+  String _title(BuildContext context) {
+    switch (type) {
+      case BottomSheetDemoType.persistent:
+        return GalleryLocalizations.of(context).demoBottomSheetPersistentTitle;
+      case BottomSheetDemoType.modal:
+        return GalleryLocalizations.of(context).demoBottomSheetModalTitle;
+    }
+    return '';
+  }
+
+  Widget _bottomSheetDemo(BuildContext context) {
+    switch (type) {
+      case BottomSheetDemoType.persistent:
+        return _PersistentBottomSheetDemo();
+        break;
+      case BottomSheetDemoType.modal:
+      default:
+        return _ModalBottomSheetDemo();
+        break;
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    // We wrap the demo in a [Navigator] to make sure that the modal bottom
+    // sheets gets dismissed when changing demo.
+    return Navigator(
+      // Adding [ValueKey] to make sure that the widget gets rebuilt when
+      // changing type.
+      key: ValueKey(type),
+      onGenerateRoute: (settings) {
+        return MaterialPageRoute<Widget>(
+          builder: (context) => Scaffold(
+            appBar: AppBar(
+              automaticallyImplyLeading: false,
+              title: Text(_title(context)),
+            ),
+            floatingActionButton: FloatingActionButton(
+              onPressed: () {},
+              backgroundColor: Theme.of(context).colorScheme.secondary,
+              child: Icon(
+                Icons.add,
+                semanticLabel:
+                    GalleryLocalizations.of(context).demoBottomSheetAddLabel,
+              ),
+            ),
+            body: _bottomSheetDemo(context),
+          ),
+          settings: settings,
+        );
+      },
+    );
+  }
+}
+
+// BEGIN bottomSheetDemoModal#1 bottomSheetDemoPersistent#1
+
+class _BottomSheetContent extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      height: 300,
+      child: Column(
+        children: [
+          Container(
+            height: 70,
+            child: Center(
+              child: Text(
+                GalleryLocalizations.of(context).demoBottomSheetHeader,
+                textAlign: TextAlign.center,
+              ),
+            ),
+          ),
+          Divider(thickness: 1),
+          Expanded(
+            child: ListView.builder(
+              itemCount: 21,
+              itemBuilder: (context, index) {
+                return ListTile(
+                  title: Text(GalleryLocalizations.of(context)
+                      .demoBottomSheetItem(index)),
+                );
+              },
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+// END bottomSheetDemoModal#1 bottomSheetDemoPersistent#1
+
+// BEGIN bottomSheetDemoModal#2
+
+class _ModalBottomSheetDemo extends StatelessWidget {
+  void _showModalBottomSheet(BuildContext context) {
+    showModalBottomSheet<void>(
+      context: context,
+      builder: (context) {
+        return _BottomSheetContent();
+      },
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: RaisedButton(
+        onPressed: () {
+          _showModalBottomSheet(context);
+        },
+        child: Text(GalleryLocalizations.of(context).demoBottomSheetButtonText),
+      ),
+    );
+  }
+}
+
+// END
+
+// BEGIN bottomSheetDemoPersistent#2
+
+class _PersistentBottomSheetDemo extends StatefulWidget {
+  @override
+  _PersistentBottomSheetDemoState createState() =>
+      _PersistentBottomSheetDemoState();
+}
+
+class _PersistentBottomSheetDemoState
+    extends State<_PersistentBottomSheetDemo> {
+  VoidCallback _showBottomSheetCallback;
+
+  @override
+  void initState() {
+    super.initState();
+    _showBottomSheetCallback = _showPersistentBottomSheet;
+  }
+
+  void _showPersistentBottomSheet() {
+    setState(() {
+      // Disable the show bottom sheet button.
+      _showBottomSheetCallback = null;
+    });
+
+    Scaffold.of(context)
+        .showBottomSheet<void>(
+          (context) {
+            return _BottomSheetContent();
+          },
+          elevation: 25,
+        )
+        .closed
+        .whenComplete(() {
+          if (mounted) {
+            setState(() {
+              // Re-enable the bottom sheet button.
+              _showBottomSheetCallback = _showPersistentBottomSheet;
+            });
+          }
+        });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: RaisedButton(
+        onPressed: _showBottomSheetCallback,
+        child: Text(GalleryLocalizations.of(context).demoBottomSheetButtonText),
+      ),
+    );
+  }
+}
+
+// END