AnimatedContainer: generalized Container widget that handles animating values

sky/sdk/lib/widgets/drawer.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 'dart:sky' as sky;
 
 import '../animation/animation_performance.dart';
 import '../animation/curves.dart';
 import '../theme/shadows.dart';
 import 'animated_component.dart';
+import 'animated_container.dart';
 import 'basic.dart';
 import 'theme.dart';
 
 // TODO(eseidel): Draw width should vary based on device size:
 // http://www.google.com/design/spec/layout/structure.html#structure-side-nav
 
 // Mobile:
 // Width = Screen width − 56 dp
 // Maximum width: 320dp
 // Maximum width applies only when using a left nav. When using a right nav,
 // the panel can cover the full width of the screen.
 
 // Desktop/Tablet:
 // Maximum width for a left nav is 400dp.
 // The right nav can vary depending on content.
 
 const double _kWidth = 304.0;
 const double _kMinFlingVelocity = 0.4;
-const int _kBaseSettleDurationMS = 246;
+const Duration _kBaseSettleDuration = const Duration(milliseconds: 246);
 // TODO(mpcomplete): The curve must be linear if we want the drawer to track
 // the user's finger. Odeon remedies this by attaching spring forces to the
 // initial timeline when animating (so it doesn't look linear).
 const Curve _kAnimationCurve = linear;
 
 typedef void DrawerStatusChangeHandler (bool showing);
 
 class DrawerController {
   DrawerController(this.onStatusChange) {
-    performance = new AnimationPerformance()
-      ..duration = new Duration(milliseconds: _kBaseSettleDurationMS)
-      ..variable = position;
+    container = new AnimatedContainer()
+      ..position = new AnimatedType<Point>(
+          new Point(-_kWidth, 0.0), end: Point.origin, curve: _kAnimationCurve);
+    performance = container.createPerformance(
+        container.position, duration: _kBaseSettleDuration);
     performance.timeline.onValueChanged.listen(_checkValue);
   }
   final DrawerStatusChangeHandler onStatusChange;
 
   AnimationPerformance performance;
-  final AnimatedPosition position = new AnimatedPosition(
-      new Point(-_kWidth, 0.0), Point.origin, curve: _kAnimationCurve);
+  AnimatedContainer container;
+
+  double get xPosition => container.position.value.x;
 
   bool _oldClosedState = true;
   void _checkValue(_) {
     var newClosedState = isClosed;
     if (onStatusChange != null && _oldClosedState != newClosedState) {
       onStatusChange(!newClosedState);
       _oldClosedState = newClosedState;
     }
   }
 
   bool get isClosed => performance.isDismissed;
-  bool get _isMostlyClosed => position.value.x <= -_kWidth/2;
+  bool get _isMostlyClosed => xPosition <= -_kWidth/2;
 
   void open() => performance.play();
 
   void close() => performance.reverse();
 
   void _settle() => _isMostlyClosed ? close() : open();
 
   void handleMaskTap(_) => close();
 
   // TODO(mpcomplete): Figure out how to generalize these handlers on a
@@ skipping 50 matching lines @@
   Widget build() {
     // TODO(mpcomplete): animate as a fade-in.
     double scaler = controller.performance.progress;
     Color maskColor = new Color.fromARGB((0x7F * scaler).floor(), 0, 0, 0);
 
     var mask = new Listener(
       child: new Container(decoration: new BoxDecoration(backgroundColor: maskColor)),
       onGestureTap: controller.handleMaskTap
     );
 
-    Widget content = controller.position.build(
+    Widget content = controller.container.build(
       new Container(
         decoration: new BoxDecoration(
           backgroundColor: Theme.of(this).canvasColor,
           boxShadow: shadows[level]),
         width: _kWidth,
         child: new Block(children)
       ));
 
     return new Listener(
       child: new Stack([ mask, content ]),
       onPointerDown: controller.handlePointerDown,
       onPointerMove: controller.handlePointerMove,
       onPointerUp: controller.handlePointerUp,
       onPointerCancel: controller.handlePointerCancel,
       onGestureFlingStart: controller.handleFlingStart
     );
   }
 
 }