add initState, rename animated_container

sky/sdk/lib/widgets/animation_builder.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:vector_math/vector_math.dart';
 
 import '../animation/animation_performance.dart';
 import '../animation/curves.dart';
 import '../base/lerp.dart';
 import '../painting/box_painter.dart';
 import '../theme/shadows.dart';
 import 'basic.dart';
 
 // This class builds a Container object from a collection of optionally-
 // animated properties. Use syncFields to update the Container's properties,
 // which will optionally animate them using an AnimationPerformance.
-class AnimatedContainer {
+class AnimationBuilder {
   AnimatedType<double> opacity;
   AnimatedType<Point> position;
   AnimatedType<double> shadow;
   AnimatedColor backgroundColor;
 
-  // These don't animate, but are used to build the Container anyway.
+  // These don't animate, but are used to build the AnimationBuilder anyway.
   double borderRadius;
   Shape shape;
 
   Map<AnimatedVariable, AnimationPerformance> _variableToPerformance =
       new Map<AnimatedVariable, AnimationPerformance>();
 
-  AnimatedContainer();
+  AnimationBuilder();
 
   AnimationPerformance createPerformance(List<AnimatedType> variables,
                                          {Duration duration}) {
     AnimationPerformance performance = new AnimationPerformance()
       ..duration = duration
       ..variable = new AnimatedList(variables);
     for (AnimatedVariable variable in variables)
       _variableToPerformance[variable] = performance;
     return performance;
   }
@@ skipping 17 matching lines @@
       current = new Transform(transform: transform, child: current);
     }
 
     if (opacity != null) {
       current = new Opacity(opacity: opacity.value, child: current);
     }
 
     return current;
   }
 
-  void syncFields(AnimatedContainer source) {
-    _syncField(position, source.position);
-    _syncField(shadow, source.shadow);
-    _syncField(backgroundColor, source.backgroundColor);
-
-    borderRadius = source.borderRadius;
-    shape = source.shape;
+  void updateFields({ AnimatedType<double> shadow,
+                      AnimatedColor backgroundColor,
+                      double borderRadius,
+                      Shape shape }) {
+    _updateField(this.shadow, shadow);
+    _updateField(this.backgroundColor, backgroundColor);
+    this.borderRadius = borderRadius;
+    this.shape = shape;
   }
 
-  void _syncField(AnimatedType variable, AnimatedType sourceVariable) {
+  void _updateField(AnimatedType variable, AnimatedType sourceVariable) {
     if (variable == null)
       return;  // TODO(mpcomplete): Should we handle transition from null?
 
     AnimationPerformance performance = _variableToPerformance[variable];
     if (performance == null) {
       // If there's no performance, no need to animate.
       if (sourceVariable != null)
         variable.value = sourceVariable.value;
       return;
     }
@@ skipping 24 matching lines @@
 
   int level1 = level.floor();
   int level2 = level.ceil();
   double t = level - level1.toDouble();
 
   List<BoxShadow> shadow = new List<BoxShadow>();
   for (int i = 0; i < shadows[level1].length; ++i)
     shadow.add(lerpBoxShadow(shadows[level1][i], shadows[level2][i], t));
   return shadow;
 }