Make the checkbox in settings control the radio buttons in the drawer, to demonstrate how to link s…

sky/examples/stocks2/lib/stock_settings.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/theme/colors.dart' as colors;
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/checkbox.dart';
 import 'package:sky/widgets/icon_button.dart';
 import 'package:sky/widgets/menu_item.dart';
 import 'package:sky/widgets/navigator.dart';
 import 'package:sky/widgets/scaffold.dart';
 import 'package:sky/widgets/theme.dart';
 import 'package:sky/widgets/tool_bar.dart';
 
+import 'stock_types.dart';
+
+typedef void SettingsUpdater({StockMode mode});
+
 class StockSettings extends Component {
 
-  StockSettings(this._navigator);
+  StockSettings(this.navigator, this.stockMode, this.updater) : super(stateful: true);
 
-  Navigator _navigator;
+  Navigator navigator;
+  StockMode stockMode;
+  SettingsUpdater updater;
 
-  bool _awesome = false;
-  void _handleAwesomeChanged(bool value) {
+  void syncFields(StockSettings source) {
+    navigator = source.navigator;
+    stockMode = source.stockMode;
+    updater = source.updater;
+  }
+
+  void _handleStockModeChanged(bool value) {
     setState(() {
-      _awesome = value;
+      stockMode = value ? StockMode.optimistic : StockMode.pessimistic;
     });
+    sendUpdates();
+  }
+
+  void sendUpdates() {
+    if (updater != null)
+      updater(
+        mode: stockMode
+      );
   }
 
   Widget buildToolBar() {
     return new ToolBar(
       left: new IconButton(
         icon: 'navigation/arrow_back_white',
-        onPressed: _navigator.pop),
+        onPressed: navigator.pop),
       center: new Text('Settings', style: Theme.of(this).text.title)
     );
   }
 
   Widget buildSettingsPane() {
     return new Container(
       padding: const EdgeDims.symmetric(vertical: 20.0),
       decoration: new BoxDecoration(backgroundColor: colors.Grey[50]),
       child: new Block([
         new MenuItem(
           icon: 'action/thumb_up',
-          onPressed: () => _handleAwesomeChanged(!_awesome),
+          onPressed: () => _handleStockModeChanged(stockMode == StockMode.optimistic ? false : true),
           children: [
             new Flexible(child: new Text('Everything is awesome')),
-            new Checkbox(value: _awesome, onChanged: _handleAwesomeChanged)
+            new Checkbox(value: stockMode == StockMode.optimistic, onChanged: _handleStockModeChanged)
           ]
         ),
       ])
     );
   }
 
   Widget build() {
     return new Scaffold(
       toolbar: buildToolBar(),
       body: buildSettingsPane()
     );
   }
 }