Animate the snack bar in the stocks app.

sky/sdk/example/stocks/lib/stock_home.dart

 // Copyright 2015 The Chromium 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:sky/editing/input.dart';
+import 'package:sky/animation/animation_performance.dart';
+import 'package:sky/widgets/animated_component.dart';
+import 'package:sky/widgets/animated_container.dart';
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/drawer.dart';
 import 'package:sky/widgets/drawer_header.dart';
 import 'package:sky/widgets/floating_action_button.dart';
 import 'package:sky/widgets/icon.dart';
 import 'package:sky/widgets/icon_button.dart';
 import 'package:sky/widgets/menu_divider.dart';
 import 'package:sky/widgets/menu_item.dart';
 import 'package:sky/widgets/modal_overlay.dart';
 import 'package:sky/widgets/navigator.dart';
 import 'package:sky/widgets/popup_menu.dart';
 import 'package:sky/widgets/radio.dart';
 import 'package:sky/widgets/snack_bar.dart';
 import 'package:sky/widgets/scaffold.dart';
 import 'package:sky/widgets/tabs.dart';
 import 'package:sky/widgets/theme.dart';
 import 'package:sky/widgets/tool_bar.dart';
 import 'package:sky/widgets/widget.dart';
 
 import 'stock_data.dart';
 import 'stock_list.dart';
 import 'stock_menu.dart';
 import 'stock_types.dart';
 
 typedef void ModeUpdater(StockMode mode);
 
-class StockHome extends StatefulComponent {
+const Duration _kSnackbarSlideDuration = const Duration(milliseconds: 200);
+
+class StockHome extends AnimatedComponent {
 
   StockHome(this.navigator, this.stocks, this.stockMode, this.modeUpdater) {
     // if (debug)
     //   new Timer(new Duration(seconds: 1), dumpState);
     _drawerController = new DrawerController(_handleDrawerStatusChanged);
   }
 
   Navigator navigator;
   List<Stock> stocks;
   StockMode stockMode;
   ModeUpdater modeUpdater;
 
   void syncFields(StockHome source) {
     navigator = source.navigator;
     stocks = source.stocks;
     stockMode = source.stockMode;
     modeUpdater = source.modeUpdater;
   }
 
   bool _isSearching = false;
   String _searchQuery;
 
-  bool _isShowingSnackBar = false;
+  AnimatedContainer _snackbarTransform;
 
   void _handleSearchBegin() {
     setState(() {
       _isSearching = true;
     });
   }
 
   void _handleSearchEnd() {
     setState(() {
       _isSearching = false;
@@ skipping 175 matching lines @@
       center: new Input(
         focused: true,
         placeholder: 'Search stocks',
         onChanged: _handleSearchQueryChanged),
       backgroundColor: Theme.of(this).canvasColor
     );
   }
 
   void _handleUndo() {
     setState(() {
-      _isShowingSnackBar = false;
+      _snackbarTransform = null;
     });
   }
 
   Widget buildSnackBar() {
-    if (!_isShowingSnackBar)
+    if (_snackbarTransform == null)
       return null;
-    return new SnackBar(
-      content: new Text("Stock purchased!"),
-      actions: [new SnackBarAction(label: "UNDO", onPressed: _handleUndo)]
-    );
+    return _snackbarTransform.build(
+      new SnackBar(
+        content: new Text("Stock purchased!"),
+        actions: [new SnackBarAction(label: "UNDO", onPressed: _handleUndo)]
+      ));
   }
 
   void _handleStockPurchased() {
     setState(() {
-      _isShowingSnackBar = true;
+      _snackbarTransform = new AnimatedContainer()
+        ..position = new AnimatedType<Point>(const Point(0.0, 45.0), end: Point.origin);
+      var performance = _snackbarTransform.createPerformance(
+          _snackbarTransform.position, duration: _kSnackbarSlideDuration);
+      watchPerformance(performance);
+      performance.play();
     });
   }
 
   Widget buildFloatingActionButton() {
-    return new FloatingActionButton(
+    var widget = new FloatingActionButton(
       child: new Icon(type: 'content/add_white', size: 24),
       onPressed: _handleStockPurchased
     );
+    if (_snackbarTransform != null)
+      widget = _snackbarTransform.build(widget);
+    return widget;
   }
 
   void addMenuToOverlays(List<Widget> overlays) {
     if (_menuController == null)
       return;
     overlays.add(new ModalOverlay(
       children: [new StockMenu(
         controller: _menuController,
         autorefresh: _autorefresh,
         onAutorefreshChanged: _handleAutorefreshChanged
       )],
       onDismiss: _handleMenuHide));
   }
 
   Widget build() {
     List<Widget> overlays = [
       new Scaffold(
         toolbar: _isSearching ? buildSearchBar() : buildToolBar(),
         body: buildTabNavigator(),
         snackBar: buildSnackBar(),
         floatingActionButton: buildFloatingActionButton(),
         drawer: _drawerShowing ? buildDrawer() : null
       ),
     ];
     addMenuToOverlays(overlays);
     return new Stack(overlays);
   }
 }