Switch Navigator over to using AnimationController

This patch moves Navigator and related code over to using
AnimationController.

packages/flutter/lib/animation.dart

@@ -8,6 +8,7 @@
 library animation;
 
 export 'src/animation/animated_value.dart';
+export 'src/animation/animations.dart';
 export 'src/animation/clamped_simulation.dart';
 export 'src/animation/curves.dart';
 export 'src/animation/forces.dart';

packages/flutter/lib/src/animation/animations.dart

+// Copyright 2016 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:ui' show VoidCallback;
+
+import 'animated_value.dart';
+import 'listener_helpers.dart';
+import 'tween.dart';
+
+class AlwaysCompleteAnimation extends Animated<double> {
+  const AlwaysCompleteAnimation();
+
+  // this performance never changes state
+  void addListener(VoidCallback listener) { }
+  void removeListener(VoidCallback listener) { }
+  void addStatusListener(PerformanceStatusListener listener) { }
+  void removeStatusListener(PerformanceStatusListener listener) { }
+  PerformanceStatus get status => PerformanceStatus.completed;
+  AnimationDirection get direction => AnimationDirection.forward;
+  double get value => 1.0;
+}
+
+const AlwaysCompleteAnimation kAlwaysCompleteAnimation = const AlwaysCompleteAnimation();
+
+class AlwaysDismissedAnimation extends Animated<double> {
+  const AlwaysDismissedAnimation();
+
+  // this performance never changes state
+  void addListener(VoidCallback listener) { }
+  void removeListener(VoidCallback listener) { }
+  void addStatusListener(PerformanceStatusListener listener) { }
+  void removeStatusListener(PerformanceStatusListener listener) { }
+  PerformanceStatus get status => PerformanceStatus.dismissed;
+  AnimationDirection get direction => AnimationDirection.forward;
+  double get value => 0.0;
+}
+
+const AlwaysDismissedAnimation kAlwaysDismissedAnimation = const AlwaysDismissedAnimation();
+
+class ProxyAnimation extends Animated<double>
+  with LazyListenerMixin, LocalPerformanceListenersMixin, LocalPerformanceStatusListenersMixin {
+  ProxyAnimation([Animated<double> animation]) {
+    _masterAnimation = animation;
+    if (_masterAnimation == null) {
+      _status = PerformanceStatus.dismissed;
+      _direction = AnimationDirection.forward;
+      _value = 0.0;
+    }
+  }
+
+  PerformanceStatus _status;
+  AnimationDirection _direction;
+  double _value;
+
+  Animated<double> get masterAnimation => _masterAnimation;
+  Animated<double> _masterAnimation;
+  void set masterAnimation(Animated<double> value) {
+    if (value == _masterAnimation)
+      return;
+    if (_masterAnimation != null) {
+      _status = _masterAnimation.status;
+      _direction = _masterAnimation.direction;
+      _value = _masterAnimation.value;
+      if (isListening)
+        didStopListening();
+    }
+    _masterAnimation = value;
+    if (_masterAnimation != null) {
+      if (isListening)
+        didStartListening();
+      if (_value != _masterAnimation.value)
+        notifyListeners();
+      if (_status != _masterAnimation.status)
+        notifyStatusListeners(_masterAnimation.status);
+      _status = null;
+      _direction = null;
+      _value = null;
+    }
+  }
+
+  void didStartListening() {
+    if (_masterAnimation != null) {
+      _masterAnimation.addListener(notifyListeners);
+      _masterAnimation.addStatusListener(notifyStatusListeners);
+    }
+  }
+
+  void didStopListening() {
+    if (_masterAnimation != null) {
+      _masterAnimation.removeListener(notifyListeners);
+      _masterAnimation.removeStatusListener(notifyStatusListeners);
+    }
+  }
+
+  PerformanceStatus get status => _masterAnimation != null ? _masterAnimation.status : _status;
+  AnimationDirection get direction => _masterAnimation != null ? _masterAnimation.direction : _direction;
+  double get value => _masterAnimation != null ? _masterAnimation.value : _value;
+}
+
+class ReverseAnimation extends Animated<double>
+  with LazyListenerMixin, LocalPerformanceStatusListenersMixin {
+  ReverseAnimation(this.masterAnimation);
+
+  final Animated<double> masterAnimation;
+
+  void addListener(VoidCallback listener) {
+    didRegisterListener();
+    masterAnimation.addListener(listener);
+  }
+  void removeListener(VoidCallback listener) {
+    masterAnimation.removeListener(listener);
+    didUnregisterListener();
+  }
+
+  void didStartListening() {
+    masterAnimation.addStatusListener(_statusChangeHandler);
+  }
+
+  void didStopListening() {
+    masterAnimation.removeStatusListener(_statusChangeHandler);
+  }
+
+  void _statusChangeHandler(PerformanceStatus status) {
+    notifyStatusListeners(_reverseStatus(status));
+  }
+
+  PerformanceStatus get status => _reverseStatus(masterAnimation.status);
+  AnimationDirection get direction => _reverseDirection(masterAnimation.direction);
+  double get value => 1.0 - masterAnimation.value;
+
+  PerformanceStatus _reverseStatus(PerformanceStatus status) {
+    switch (status) {
+      case PerformanceStatus.forward: return PerformanceStatus.reverse;
+      case PerformanceStatus.reverse: return PerformanceStatus.forward;
+      case PerformanceStatus.completed: return PerformanceStatus.dismissed;
+      case PerformanceStatus.dismissed: return PerformanceStatus.completed;
+    }
+  }
+
+  AnimationDirection _reverseDirection(AnimationDirection direction) {
+    switch (direction) {
+      case AnimationDirection.forward: return AnimationDirection.reverse;
+      case AnimationDirection.reverse: return AnimationDirection.forward;
+    }
+  }
+}
+
+enum _TrainHoppingMode { minimize, maximize }
+
+/// This animation starts by proxying one animation, but can be given a
+/// second animation. When their times cross (either because the second is
+/// going in the opposite direction, or because the one overtakes the other),
+/// the animation hops over to proxying the second animation, and the second
+/// animation becomes the new "first" performance.
+///
+/// Since this object must track the two animations even when it has no
+/// listeners of its own, instead of shutting down when all its listeners are
+/// removed, it exposes a [dispose()] method. Call this method to shut this
+/// object down.
+class TrainHoppingAnimation extends Animated<double>
+  with EagerListenerMixin, LocalPerformanceListenersMixin, LocalPerformanceStatusListenersMixin {
+  TrainHoppingAnimation(this._currentTrain, this._nextTrain, { this.onSwitchedTrain }) {
+    assert(_currentTrain != null);
+    if (_nextTrain != null) {
+      if (_currentTrain.value > _nextTrain.value) {
+        _mode = _TrainHoppingMode.maximize;
+      } else {
+        _mode = _TrainHoppingMode.minimize;
+        if (_currentTrain.value == _nextTrain.value) {
+          _currentTrain = _nextTrain;
+          _nextTrain = null;
+        }
+      }
+    }
+    _currentTrain.addStatusListener(_statusChangeHandler);
+    _currentTrain.addListener(_valueChangeHandler);
+    if (_nextTrain != null)
+      _nextTrain.addListener(_valueChangeHandler);
+    assert(_mode != null);
+  }
+
+  Animated<double> get currentTrain => _currentTrain;
+  Animated<double> _currentTrain;
+  Animated<double> _nextTrain;
+  _TrainHoppingMode _mode;
+
+  VoidCallback onSwitchedTrain;
+
+  PerformanceStatus _lastStatus;
+  void _statusChangeHandler(PerformanceStatus status) {
+    assert(_currentTrain != null);
+    if (status != _lastStatus) {
+      notifyListeners();
+      _lastStatus = status;
+    }
+    assert(_lastStatus != null);
+  }
+
+  PerformanceStatus get status => _currentTrain.status;
+  AnimationDirection get direction => _currentTrain.direction;
+
+  double _lastValue;
+  void _valueChangeHandler() {
+    assert(_currentTrain != null);
+    bool hop = false;
+    if (_nextTrain != null) {
+      switch (_mode) {
+        case _TrainHoppingMode.minimize:
+          hop = _nextTrain.value <= _currentTrain.value;
+          break;
+        case _TrainHoppingMode.maximize:
+          hop = _nextTrain.value >= _currentTrain.value;
+          break;
+      }
+      if (hop) {
+        _currentTrain.removeStatusListener(_statusChangeHandler);
+        _currentTrain.removeListener(_valueChangeHandler);
+        _currentTrain = _nextTrain;
+        _nextTrain.addListener(_valueChangeHandler);
+        _statusChangeHandler(_nextTrain.status);
+      }
+    }
+    double newValue = value;
+    if (newValue != _lastValue) {
+      notifyListeners();
+      _lastValue = newValue;
+    }
+    assert(_lastValue != null);
+    if (hop && onSwitchedTrain != null)
+      onSwitchedTrain();
+  }
+
+  double get value => _currentTrain.value;
+
+  /// Frees all the resources used by this performance.
+  /// After this is called, this object is no longer usable.
+  void dispose() {
+    assert(_currentTrain != null);
+    _currentTrain.removeStatusListener(_statusChangeHandler);
+    _currentTrain.removeListener(_valueChangeHandler);
+    _currentTrain = null;
+    if (_nextTrain != null) {
+      _nextTrain.removeListener(_valueChangeHandler);
+      _nextTrain = null;
+    }
+  }
+}

packages/flutter/lib/src/animation/tween.dart

@@ -97,7 +97,7 @@ abstract class Evaluatable<T> {
 
   T evaluate(Animated<double> animation);
 
-  Animated<T> watch(Animated<double> parent) {
+  Animated<T> animate(Animated<double> parent) {
     return new _AnimatedEvaluation<T>(parent, this);
   }
 }
@@ -258,7 +258,11 @@ class _RepeatingSimulation extends Simulation {
 }
 
 class CurvedAnimation extends Animated<double> with ProxyAnimatedMixin {
-  CurvedAnimation({ this.parent, this.curve, this.reverseCurve }) {
+  CurvedAnimation({
+    this.parent,
+    this.curve: Curves.linear,
+    this.reverseCurve
+  }) {
     assert(parent != null);
     assert(curve != null);
     parent.addStatusListener(_handleStatusChanged);
@@ -373,3 +377,18 @@ class IntTween extends Tween<int> {
   // the begin and end types by a double, and int * double returns a double.
   int lerp(double t) => (begin + (end - begin) * t).round();
 }
+
+class CurveTween extends Evaluatable<double> {
+  CurveTween({ this.curve });
+
+  Curve curve;
+
+  double evaluate(Animated<double> animation) {
+    double t = animation.value;
+    if (t == 0.0 || t == 1.0) {
+      assert(curve.transform(t).round() == t);
+      return t;
+    }
+    return curve.transform(t);
+  }
+}

packages/flutter/lib/src/material/bottom_sheet.dart

@@ -129,41 +129,17 @@ class _ModalBottomSheet extends StatefulComponent {
 }
 
 class _ModalBottomSheetState extends State<_ModalBottomSheet> {
-  // TODO(abarth): Delete _controllerPerformanceAdaptor when navigator uses
-  // AnimationController and friends.
-  AnimationController _controllerPerformanceAdaptor;
-
-  void initState() {
-    super.initState();
-    _controllerPerformanceAdaptor = new AnimationController();
-    _updateControllerPerformanceAdaptor();
-  }
-
-  void didUpdateConfig(_ModalBottomSheet oldConfig) {
-    if (config.route.performance != oldConfig.route.performance)
-      _updateControllerPerformanceAdaptor();
-  }
-
-  void _updateControllerPerformanceAdaptor() {
-    Performance performance = config.route.performance;
-    _controllerPerformanceAdaptor
-      ..duration = performance.duration
-      ..value = performance.progress;
-    if (performance.isAnimating)
-      _controllerPerformanceAdaptor.play(performance.direction);
-  }
-
   Widget build(BuildContext context) {
     return new GestureDetector(
       onTap: () => Navigator.pop(context),
       child: new AnimatedBuilder(
-        animation: _controllerPerformanceAdaptor,
+        animation: config.route.animation,
         builder: (BuildContext context) {
           return new ClipRect(
             child: new CustomOneChildLayout(
-              delegate: new _ModalBottomSheetLayout(config.route.performance.progress),
+              delegate: new _ModalBottomSheetLayout(config.route.animation.value),
               child: new BottomSheet(
-                animationController: _controllerPerformanceAdaptor,
+                animationController: config.route.animation,
                 onClosing: () => Navigator.pop(context),
                 builder: config.route.builder
               )
@@ -191,7 +167,7 @@ class _ModalBottomSheetRoute<T> extends PopupRoute<T> {
     return BottomSheet.createAnimationController();
   }
 
-  Widget buildPage(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance) {
+  Widget buildPage(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation) {
     return new _ModalBottomSheet(route: this);
   }
 }

packages/flutter/lib/src/material/dialog.dart

@@ -128,14 +128,16 @@ class _DialogRoute<T> extends PopupRoute<T> {
   bool get barrierDismissable => true;
   Color get barrierColor => Colors.black54;
 
-  Widget buildPage(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance) {
+  Widget buildPage(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation) {
     return child;
   }
 
-  Widget buildTransitions(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance, Widget child) {
-    return new OldFadeTransition(
-      performance: performance,
-      opacity: new AnimatedValue<double>(0.0, end: 1.0, curve: Curves.easeOut),
+  Widget buildTransitions(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation, Widget child) {
+    return new FadeTransition(
+      opacity: new CurvedAnimation(
+        parent: animation,
+        curve: Curves.easeOut
+      ),
       child: child
     );
   }

packages/flutter/lib/src/material/dropdown.dart

@@ -62,7 +62,7 @@ class _DropDownMenu<T> extends StatusTransitionComponent {
   _DropDownMenu({
     Key key,
     _DropDownRoute<T> route
-  }) : route = route, super(key: key, performance: route.performance);
+  }) : route = route, super(key: key, animation: route.animation);
 
   final _DropDownRoute<T> route;
 
@@ -79,16 +79,15 @@ class _DropDownMenu<T> extends StatusTransitionComponent {
     final double unit = 0.5 / (route.items.length + 1.5);
     final List<Widget> children = <Widget>[];
     for (int itemIndex = 0; itemIndex < route.items.length; ++itemIndex) {
-      AnimatedValue<double> opacity;
+      CurvedAnimation opacity;
       if (itemIndex == route.selectedIndex) {
-        opacity = new AnimatedValue<double>(0.0, end: 1.0, curve: const Interval(0.0, 0.001), reverseCurve: const Interval(0.75, 1.0));
+        opacity = new CurvedAnimation(parent: route.animation, curve: const Interval(0.0, 0.001), reverseCurve: const Interval(0.75, 1.0));
       } else {
         final double start = (0.5 + (itemIndex + 1) * unit).clamp(0.0, 1.0);
         final double end = (start + 1.5 * unit).clamp(0.0, 1.0);
-        opacity = new AnimatedValue<double>(0.0, end: 1.0, curve: new Interval(start, end), reverseCurve: const Interval(0.75, 1.0));
+        opacity = new CurvedAnimation(parent: route.animation, curve: new Interval(start, end), reverseCurve: const Interval(0.75, 1.0));
       }
-      children.add(new OldFadeTransition(
-        performance: route.performance,
+      children.add(new FadeTransition(
         opacity: opacity,
         child: new InkWell(
           child: new Container(
@@ -103,42 +102,45 @@ class _DropDownMenu<T> extends StatusTransitionComponent {
       ));
     }
 
-    final AnimatedValue<double> menuOpacity = new AnimatedValue<double>(0.0,
-      end: 1.0,
+    final CurvedAnimation opacity = new CurvedAnimation(
+      parent: route.animation,
       curve: const Interval(0.0, 0.25),
       reverseCurve: const Interval(0.75, 1.0)
     );
 
-    final AnimatedValue<double> menuTop = new AnimatedValue<double>(route.rect.top,
-      end: route.rect.top - route.selectedIndex * route.rect.height,
+    final CurvedAnimation resize = new CurvedAnimation(
+      parent: route.animation,
       curve: const Interval(0.25, 0.5),
       reverseCurve: const Interval(0.0, 0.001)
     );
-    final AnimatedValue<double> menuBottom = new AnimatedValue<double>(route.rect.bottom,
-      end: menuTop.end + route.items.length * route.rect.height,
-      curve: const Interval(0.25, 0.5),
-      reverseCurve: const Interval(0.0, 0.001)
+
+    final Tween<double> menuTop = new Tween<double>(
+      begin: route.rect.top,
+      end: route.rect.top - route.selectedIndex * route.rect.height
+    );
+    final Tween<double> menuBottom = new Tween<double>(
+      begin: route.rect.bottom,
+      end: menuTop.end + route.items.length * route.rect.height
     );
 
-    return new OldFadeTransition(
-      performance: route.performance,
-      opacity: menuOpacity,
-      child: new BuilderTransition(
-        performance: route.performance,
-        variables: <AnimatedValue<double>>[menuTop, menuBottom],
+    Widget child = new Material(
+      type: MaterialType.transparency,
+      child: new Block(children)
+    );
+    return new FadeTransition(
+      opacity: opacity,
+      child: new AnimatedBuilder(
+        animation: resize,
         builder: (BuildContext context) {
           return new CustomPaint(
             painter: new _DropDownMenuPainter(
               color: Theme.of(context).canvasColor,
               elevation: route.elevation,
-              menuTop: menuTop.value,
-              menuBottom: menuBottom.value,
+              menuTop: menuTop.evaluate(resize),
+              menuBottom: menuBottom.evaluate(resize),
               renderBox: context.findRenderObject()
             ),
-            child: new Material(
-              type: MaterialType.transparency,
-              child: new Block(children)
-            )
+            child: child
           );
         }
       )
@@ -190,7 +192,7 @@ class _DropDownRoute<T> extends PopupRoute<_DropDownRouteResult<T>> {
     );
   }
 
-  Widget buildPage(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance) {
+  Widget buildPage(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation) {
     return new _DropDownMenu(route: this);
   }
 }

packages/flutter/lib/src/material/floating_action_button.dart

@@ -40,20 +40,29 @@ class FloatingActionButton extends StatefulComponent {
 }
 
 class _FloatingActionButtonState extends State<FloatingActionButton> {
-  final Performance _childSegue = new Performance(duration: _kChildSegue);
+  Animated<double> _childSegue;
+  AnimationController _childSegueController;
 
   void initState() {
     super.initState();
-    _childSegue.play();
+    _childSegueController = new AnimationController(duration: _kChildSegue)
+      ..forward();
+    _childSegue = new Tween<double>(
+      begin: -0.125,
+      end: 0.0
+    ).animate(new CurvedAnimation(
+      parent: _childSegueController,
+      curve: _kChildSegueInterval
+    ));
   }
 
   void didUpdateConfig(FloatingActionButton oldConfig) {
     super.didUpdateConfig(oldConfig);
     if (Widget.canUpdate(oldConfig.child, config.child) && config.backgroundColor == oldConfig.backgroundColor)
       return;
-    _childSegue
-      ..progress = 0.0
-      ..play();
+    _childSegueController
+      ..value = 0.0
+      ..forward();
   }
 
   bool _highlight = false;
@@ -87,8 +96,7 @@ class _FloatingActionButtonState extends State<FloatingActionButton> {
             child: new IconTheme(
               data: new IconThemeData(color: iconThemeColor),
               child: new RotationTransition(
-                performance: _childSegue,
-                turns: new AnimatedValue<double>(-0.125, end: 0.0, curve: _kChildSegueInterval),
+                turns: _childSegue,
                 child: config.child
               )
             )

packages/flutter/lib/src/material/page.dart

@@ -7,31 +7,32 @@ import 'dart:async';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';
 
-class _MaterialPageTransition extends TransitionWithChild {
+class _MaterialPageTransition extends AnimatedComponent {
   _MaterialPageTransition({
     Key key,
-    PerformanceView performance,
-    Widget child
-  }) : super(key: key,
-             performance: performance,
-             child: child);
+    Animated<double> animation,
+    this.child
+  }) : super(
+    key: key,
+    animation: new CurvedAnimation(parent: animation, curve: Curves.easeOut)
+  );
 
-  final AnimatedValue<Point> _position =
-     new AnimatedValue<Point>(const Point(0.0, 75.0), end: Point.origin, curve: Curves.easeOut);
+  final Widget child;
 
-  final AnimatedValue<double> _opacity =
-     new AnimatedValue<double>(0.0, end: 1.0, curve: Curves.easeOut);
+  final Tween<Point> _position = new Tween<Point>(
+    begin: const Point(0.0, 75.0),
+    end: Point.origin
+  );
 
-  Widget buildWithChild(BuildContext context, Widget child) {
-    performance.updateVariable(_position);
-    performance.updateVariable(_opacity);
+  Widget build(BuildContext context) {
+    Point position = _position.evaluate(animation);
     Matrix4 transform = new Matrix4.identity()
-      ..translate(_position.value.x, _position.value.y);
+      ..translate(position.x, position.y);
     return new Transform(
       transform: transform,
       // TODO(ianh): tell the transform to be un-transformed for hit testing
       child: new Opacity(
-        opacity: _opacity.value,
+        opacity: animation.value,
         child: child
       )
     );
@@ -56,7 +57,7 @@ class MaterialPageRoute<T> extends PageRoute<T> {
   Color get barrierColor => null;
   bool canTransitionFrom(TransitionRoute nextRoute) => false;
 
-  Widget buildPage(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance) {
+  Widget buildPage(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation) {
     Widget result = builder(context);
     assert(() {
       if (result == null)
@@ -67,9 +68,9 @@ class MaterialPageRoute<T> extends PageRoute<T> {
     return result;
   }
 
-  Widget buildTransitions(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance, Widget child) {
+  Widget buildTransitions(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation, Widget child) {
     return new _MaterialPageTransition(
-      performance: performance,
+      animation: animation,
       child: child
     );
   }

packages/flutter/lib/src/material/popup_menu.dart

@@ -61,9 +61,12 @@ class _PopupMenu<T> extends StatelessComponent {
     for (int i = 0; i < route.items.length; ++i) {
       double start = (i + 1) * unit;
       double end = (start + 1.5 * unit).clamp(0.0, 1.0);
-      children.add(new OldFadeTransition(
-        performance: route.performance,
-        opacity: new AnimatedValue<double>(0.0, end: 1.0, curve: new Interval(start, end)),
+      CurvedAnimation opacity = new CurvedAnimation(
+        parent: route.animation,
+        curve: new Interval(start, end)
+      );
+      children.add(new FadeTransition(
+        opacity: opacity,
         child: new InkWell(
           onTap: () => Navigator.pop(context, route.items[i].value),
           child: route.items[i]
@@ -71,24 +74,11 @@ class _PopupMenu<T> extends StatelessComponent {
       );
     }
 
-    final AnimatedValue<double> opacity = new AnimatedValue<double>(0.0, end: 1.0, curve: new Interval(0.0, 1.0 / 3.0));
-    final AnimatedValue<double> width = new AnimatedValue<double>(0.0, end: 1.0, curve: new Interval(0.0, unit));
-    final AnimatedValue<double> height = new AnimatedValue<double>(0.0, end: 1.0, curve: new Interval(0.0, unit * route.items.length));
+    final CurveTween opacity = new CurveTween(curve: new Interval(0.0, 1.0 / 3.0));
+    final CurveTween width = new CurveTween(curve: new Interval(0.0, unit));
+    final CurveTween height = new CurveTween(curve: new Interval(0.0, unit * route.items.length));
 
-    return new BuilderTransition(
-      performance: route.performance,
-      variables: <AnimatedValue<double>>[opacity, width, height],
-      builder: (BuildContext context) {
-        return new Opacity(
-          opacity: opacity.value,
-          child: new Material(
-            type: MaterialType.card,
-            elevation: route.elevation,
-            child: new Align(
-              alignment: const FractionalOffset(1.0, 0.0),
-              widthFactor: width.value,
-              heightFactor: height.value,
-              child: new ConstrainedBox(
+    Widget child = new ConstrainedBox(
       constraints: new BoxConstraints(
         minWidth: _kMenuMinWidth,
         maxWidth: _kMenuMaxWidth
@@ -102,7 +92,21 @@ class _PopupMenu<T> extends StatelessComponent {
           )
         )
       )
-              )
+    );
+
+    return new AnimatedBuilder(
+      animation: route.animation,
+      builder: (BuildContext context) {
+        return new Opacity(
+          opacity: opacity.evaluate(route.animation),
+          child: new Material(
+            type: MaterialType.card,
+            elevation: route.elevation,
+            child: new Align(
+              alignment: const FractionalOffset(1.0, 0.0),
+              widthFactor: width.evaluate(route.animation),
+              heightFactor: height.evaluate(route.animation),
+              child: child
             )
           )
         );
@@ -127,9 +131,9 @@ class _PopupMenuRoute<T> extends PopupRoute<T> {
     return position;
   }
 
-  PerformanceView createPerformance() {
-    return new CurvedPerformance(
-      super.createPerformance(),
+  Animated<double> createAnimation() {
+    return new CurvedAnimation(
+      parent: super.createAnimation(),
       reverseCurve: new Interval(0.0, _kMenuCloseIntervalEnd)
     );
   }
@@ -138,7 +142,7 @@ class _PopupMenuRoute<T> extends PopupRoute<T> {
   bool get barrierDismissable => true;
   Color get barrierColor => null;
 
-  Widget buildPage(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance) {
+  Widget buildPage(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation) {
     return new _PopupMenu(route: this);
   }
 }

packages/flutter/lib/src/material/scaffold.dart

@@ -145,7 +145,7 @@ class _FloatingActionButtonTransitionState extends State<_FloatingActionButtonTr
         scale: new Tween<double>(
           begin: 1.0,
           end: 0.0
-        ).watch(new CurvedAnimation(
+        ).animate(new CurvedAnimation(
           parent: controller,
           curve: const Interval(0.0, 0.5, curve: Curves.easeIn)
         )),

packages/flutter/lib/src/widgets/heroes.dart

@@ -73,7 +73,7 @@ class _HeroManifest {
 
 abstract class HeroHandle {
   bool get alwaysAnimate;
-  _HeroManifest _takeChild(Rect animationArea);
+  _HeroManifest _takeChild(Rect animationArea, Animated<double> currentAnimation);
 }
 
 class Hero extends StatefulComponent {
@@ -167,7 +167,7 @@ class HeroState extends State<Hero> implements HeroHandle {
 
   bool get alwaysAnimate => config.alwaysAnimate;
 
-  _HeroManifest _takeChild(Rect animationArea) {
+  _HeroManifest _takeChild(Rect animationArea, Animated<double> currentAnimation) {
     assert(_mode == _HeroMode.measured || _mode == _HeroMode.taken);
     final RenderBox renderObject = context.findRenderObject();
     final Point heroTopLeft = renderObject.localToGlobal(Point.origin);
@@ -256,14 +256,14 @@ class _HeroQuestState implements HeroHandle {
   final RelativeRect targetRect;
   final int targetTurns;
   final HeroState targetState;
-  final AnimatedRelativeRectValue currentRect;
-  final AnimatedValue<double> currentTurns;
+  final RelativeRectTween currentRect;
+  final Tween<double> currentTurns;
 
   bool get alwaysAnimate => true;
 
   bool get taken => _taken;
   bool _taken = false;
-  _HeroManifest _takeChild(Rect animationArea) {
+  _HeroManifest _takeChild(Rect animationArea, Animated<double> currentAnimation) {
     assert(!taken);
     _taken = true;
     Set<HeroState> states = sourceStates;
@@ -273,18 +273,16 @@ class _HeroQuestState implements HeroHandle {
       key: key,
       config: child,
       sourceStates: states,
-      currentRect: currentRect.value,
-      currentTurns: currentTurns.value
+      currentRect: currentRect.evaluate(currentAnimation),
+      currentTurns: currentTurns.evaluate(currentAnimation)
     );
   }
 
-  Widget build(BuildContext context, PerformanceView performance) {
+  Widget build(BuildContext context, Animated<double> animation) {
     return new PositionedTransition(
-      rect: currentRect,
-      performance: performance,
+      rect: currentRect.animate(animation),
       child: new RotationTransition(
-        turns: currentTurns,
-        performance: performance,
+        turns: currentTurns.animate(animation),
         child: new KeyedSubtree(
           key: key,
           child: child
@@ -317,16 +315,16 @@ class HeroParty {
     return result;
   }
 
-  AnimatedRelativeRectValue createAnimatedRelativeRect(RelativeRect begin, RelativeRect end, Curve curve) {
-    return new AnimatedRelativeRectValue(begin, end: end, curve: curve);
+  RelativeRectTween createRectTween(RelativeRect begin, RelativeRect end) {
+    return new RelativeRectTween(begin: begin, end: end);
   }
 
-  AnimatedValue<double> createAnimatedTurns(double begin, double end, Curve curve) {
+  Tween<double> createTurnsTween(double begin, double end) {
     assert(end.floor() == end);
-    return new AnimatedValue<double>(begin, end: end, curve: curve);
+    return new Tween<double>(begin: begin, end: end);
   }
 
-  void animate(Map<Object, HeroHandle> heroesFrom, Map<Object, HeroHandle> heroesTo, Rect animationArea, Curve curve) {
+  void animate(Map<Object, HeroHandle> heroesFrom, Map<Object, HeroHandle> heroesTo, Rect animationArea) {
     assert(!heroesFrom.containsKey(null));
     assert(!heroesTo.containsKey(null));
 
@@ -346,9 +344,9 @@ class HeroParty {
       if ((heroPair.from == null && !heroPair.to.alwaysAnimate) ||
           (heroPair.to == null && !heroPair.from.alwaysAnimate))
         continue;
-      _HeroManifest from = heroPair.from?._takeChild(animationArea);
+      _HeroManifest from = heroPair.from?._takeChild(animationArea, _currentAnimation);
       assert(heroPair.to == null || heroPair.to is HeroState);
-      _HeroManifest to = heroPair.to?._takeChild(animationArea);
+      _HeroManifest to = heroPair.to?._takeChild(animationArea, _currentAnimation);
       assert(from != null || to != null);
       assert(to == null || to.sourceStates.length == 1);
       assert(to == null || to.currentTurns.floor() == to.currentTurns);
@@ -369,8 +367,8 @@ class HeroParty {
         targetRect: targetRect,
         targetTurns: targetTurns.floor(),
         targetState: targetState,
-        currentRect: createAnimatedRelativeRect(sourceRect, targetRect, curve),
-        currentTurns: createAnimatedTurns(sourceTurns, targetTurns, curve)
+        currentRect: createRectTween(sourceRect, targetRect),
+        currentTurns: createTurnsTween(sourceTurns, targetTurns)
       ));
     }
 
@@ -378,19 +376,19 @@ class HeroParty {
     _heroes = _newHeroes;
   }
 
-  PerformanceView _currentPerformance;
+  Animated<double> _currentAnimation;
 
   void _clearCurrentPerformance() {
-    _currentPerformance?.removeStatusListener(_handleUpdate);
-    _currentPerformance = null;
+    _currentAnimation?.removeStatusListener(_handleUpdate);
+    _currentAnimation = null;
   }
 
-  void setPerformance(PerformanceView performance) {
-    assert(performance != null || _heroes.length == 0);
-    if (performance != _currentPerformance) {
+  void setAnimation(Animated<double> animation) {
+    assert(animation != null || _heroes.length == 0);
+    if (animation != _currentAnimation) {
       _clearCurrentPerformance();
-      _currentPerformance = performance;
-      _currentPerformance?.addStatusListener(_handleUpdate);
+      _currentAnimation = animation;
+      _currentAnimation?.addStatusListener(_handleUpdate);
     }
   }
 
@@ -419,7 +417,7 @@ class HeroController extends NavigatorObserver {
   }
 
   HeroParty _party;
-  PerformanceView _performance;
+  Animated<double> _animation;
   PageRoute _from;
   PageRoute _to;
 
@@ -429,11 +427,11 @@ class HeroController extends NavigatorObserver {
     assert(navigator != null);
     assert(route != null);
     if (route is PageRoute) {
-      assert(route.performance != null);
+      assert(route.animation != null);
       if (previousRoute is PageRoute) // could be null
         _from = previousRoute;
       _to = route;
-      _performance = route.performance;
+      _animation = route.animation;
       _checkForHeroQuest();
     }
   }
@@ -442,11 +440,11 @@ class HeroController extends NavigatorObserver {
     assert(navigator != null);
     assert(route != null);
     if (route is PageRoute) {
-      assert(route.performance != null);
+      assert(route.animation != null);
       if (previousRoute is PageRoute) {
         _to = previousRoute;
         _from = route;
-        _performance = route.performance;
+        _animation = route.animation;
         _checkForHeroQuest();
       }
     }
@@ -454,7 +452,7 @@ class HeroController extends NavigatorObserver {
 
   void _checkForHeroQuest() {
     if (_from != null && _to != null && _from != _to) {
-      _to.offstage = _to.performance.status != PerformanceStatus.completed;
+      _to.offstage = _to.animation.status != PerformanceStatus.completed;
       Scheduler.instance.addPostFrameCallback(_updateQuest);
     }
   }
@@ -463,7 +461,7 @@ class HeroController extends NavigatorObserver {
     _removeHeroesFromOverlay();
     _from = null;
     _to = null;
-    _performance = null;
+    _animation = null;
   }
 
   Rect _getAnimationArea(BuildContext context) {
@@ -481,7 +479,7 @@ class HeroController extends NavigatorObserver {
 
   void _addHeroToOverlay(Widget hero, Object tag, OverlayState overlay) {
     OverlayEntry entry = new OverlayEntry(builder: (_) => hero);
-    if (_performance.direction == AnimationDirection.forward)
+    if (_animation.direction == AnimationDirection.forward)
       _to.insertHeroOverlayEntry(entry, tag, overlay);
     else
       _from.insertHeroOverlayEntry(entry, tag, overlay);
@@ -507,18 +505,21 @@ class HeroController extends NavigatorObserver {
     Map<Object, HeroHandle> heroesTo = Hero.of(_to.subtreeContext, mostValuableKeys);
     _to.offstage = false;
 
-    PerformanceView performance = _performance;
+    Animated<double> animation = _animation;
     Curve curve = Curves.ease;
-    if (performance.status == PerformanceStatus.reverse) {
-      performance = new ReversePerformance(performance);
-      curve = new Interval(performance.progress, 1.0, curve: curve);
+    if (animation.status == PerformanceStatus.reverse) {
+      animation = new ReverseAnimation(animation);
+      curve = new Interval(animation.value, 1.0, curve: curve);
     }
 
-    _party.animate(heroesFrom, heroesTo, _getAnimationArea(navigator.context), curve);
+    _party.animate(heroesFrom, heroesTo, _getAnimationArea(navigator.context));
     _removeHeroesFromOverlay();
-    _party.setPerformance(performance);
+    _party.setAnimation(new CurvedAnimation(
+      parent: animation,
+      curve: curve
+    ));
     for (_HeroQuestState hero in _party._heroes) {
-      Widget widget = hero.build(navigator.context, performance);
+      Widget widget = hero.build(navigator.context, animation);
       _addHeroToOverlay(widget, hero.tag, navigator.overlay);
     }
   }

packages/flutter/lib/src/widgets/modal_barrier.dart

@@ -43,38 +43,23 @@ class ModalBarrier extends StatelessComponent {
 }
 
 /// Prevents the user from interacting with widgets behind itself.
-class AnimatedModalBarrier extends StatelessComponent {
+class AnimatedModalBarrier extends AnimatedComponent {
   AnimatedModalBarrier({
     Key key,
-    this.color,
-    this.performance,
+    Animated<Color> color,
     this.dismissable: true
-  }) : super(key: key);
+  }) : color = color, super(key: key, animation: color);
 
   /// If non-null, fill the barrier with this color.
-  ///
-  /// The barrier will animate this color according to the given [performance].
-  final AnimatedColorValue color;
-
-  /// The performance to use when animating the given [color].
-  final PerformanceView performance;
+  final Animated<Color> color;
 
   /// Whether touching the barrier will pop the current route off the [Navigator].
   final bool dismissable;
 
   Widget build(BuildContext context) {
-    return new BuilderTransition(
-      performance: performance,
-      variables: <AnimatedColorValue>[color],
-      builder: (BuildContext context) {
-        return new IgnorePointer(
-          ignoring: performance.status == PerformanceStatus.reverse,
-          child: new ModalBarrier(
+    return new ModalBarrier(
       color: color.value,
       dismissable: dismissable
-          )
-        );
-      }
     );
   }
 }

packages/flutter/lib/src/widgets/pages.dart

@@ -21,11 +21,11 @@ abstract class PageRoute<T> extends ModalRoute<T> {
   bool canTransitionTo(TransitionRoute nextRoute) => nextRoute is PageRoute;
   bool canTransitionFrom(TransitionRoute nextRoute) => nextRoute is PageRoute;
 
-  Performance createPerformanceController() {
-    Performance performance = super.createPerformanceController();
+  AnimationController createAnimationController() {
+    AnimationController controller = super.createAnimationController();
     if (settings.isInitialRoute)
-      performance.progress = 1.0;
-    return performance;
+      controller.value = 1.0;
+    return controller;
   }
 
   /// Subclasses can override this method to customize how heroes are inserted.

packages/flutter/lib/src/widgets/routes.dart

@@ -92,25 +92,25 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
   Duration get transitionDuration;
   bool get opaque;
 
-  PerformanceView get performance => _performance;
-  Performance _performanceController;
-  PerformanceView _performance;
+  Animated<double> get animation => _animation;
+  Animated<double> _animation;
+  AnimationController _controller;
 
   /// Called to create the Performance object that will drive the transitions to
   /// this route from the previous one, and back to the previous route from this
   /// one.
-  Performance createPerformanceController() {
+  AnimationController createAnimationController() {
     Duration duration = transitionDuration;
     assert(duration != null && duration >= Duration.ZERO);
-    return new Performance(duration: duration, debugLabel: debugLabel);
+    return new AnimationController(duration: duration, debugLabel: debugLabel);
   }
 
   /// Called to create the PerformanceView that exposes the current progress of
   /// the transition controlled by the Performance object created by
-  /// [createPerformanceController()].
-  PerformanceView createPerformance() {
-    assert(_performanceController != null);
-    return _performanceController.view;
+  /// [createAnimationController()].
+  Animated<double> createAnimation() {
+    assert(_controller != null);
+    return _controller.view;
   }
 
   T _result;
@@ -134,33 +134,33 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
     }
   }
 
-  PerformanceView get forwardPerformance => _forwardPerformance;
-  final ProxyPerformance _forwardPerformance = new ProxyPerformance(alwaysDismissedPerformance);
+  Animated<double> get forwardAnimation => _forwardAnimation;
+  final ProxyAnimation _forwardAnimation = new ProxyAnimation(kAlwaysDismissedAnimation);
 
   void install(OverlayEntry insertionPoint) {
-    _performanceController = createPerformanceController();
-    assert(_performanceController != null);
-    _performance = createPerformance();
-    assert(_performance != null);
+    _controller = createAnimationController();
+    assert(_controller != null);
+    _animation = createAnimation();
+    assert(_animation != null);
     super.install(insertionPoint);
   }
 
   void didPush() {
-    _performance.addStatusListener(handleStatusChanged);
-    _performanceController.forward();
+    _animation.addStatusListener(handleStatusChanged);
+    _controller.forward();
     super.didPush();
   }
 
   void didReplace(Route oldRoute) {
     if (oldRoute is TransitionRoute)
-      _performanceController.progress = oldRoute._performanceController.progress;
-    _performance.addStatusListener(handleStatusChanged);
+      _controller.value = oldRoute._controller.value;
+    _animation.addStatusListener(handleStatusChanged);
     super.didReplace(oldRoute);
   }
 
   bool didPop(T result) {
     _result = result;
-    _performanceController.reverse();
+    _controller.reverse();
     _popCompleter?.complete(_result);
     return true;
   }
@@ -177,30 +177,30 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
 
   void _updateForwardPerformance(Route nextRoute) {
     if (nextRoute is TransitionRoute && canTransitionTo(nextRoute) && nextRoute.canTransitionFrom(this)) {
-      PerformanceView current = _forwardPerformance.masterPerformance;
+      Animated<double> current = _forwardAnimation.masterAnimation;
       if (current != null) {
-        if (current is TrainHoppingPerformance) {
-          TrainHoppingPerformance newPerformance;
-          newPerformance = new TrainHoppingPerformance(
+        if (current is TrainHoppingAnimation) {
+          TrainHoppingAnimation newPerformance;
+          newPerformance = new TrainHoppingAnimation(
             current.currentTrain,
-            nextRoute.performance,
+            nextRoute.animation,
             onSwitchedTrain: () {
-              assert(_forwardPerformance.masterPerformance == newPerformance);
-              assert(newPerformance.currentTrain == nextRoute.performance);
-              _forwardPerformance.masterPerformance = newPerformance.currentTrain;
+              assert(_forwardAnimation.masterAnimation == newPerformance);
+              assert(newPerformance.currentTrain == nextRoute.animation);
+              _forwardAnimation.masterAnimation = newPerformance.currentTrain;
               newPerformance.dispose();
             }
           );
-          _forwardPerformance.masterPerformance = newPerformance;
+          _forwardAnimation.masterAnimation = newPerformance;
           current.dispose();
         } else {
-          _forwardPerformance.masterPerformance = new TrainHoppingPerformance(current, nextRoute.performance);
+          _forwardAnimation.masterAnimation = new TrainHoppingAnimation(current, nextRoute.animation);
         }
       } else {
-        _forwardPerformance.masterPerformance = nextRoute.performance;
+        _forwardAnimation.masterAnimation = nextRoute.animation;
       }
     } else {
-      _forwardPerformance.masterPerformance = alwaysDismissedPerformance;
+      _forwardAnimation.masterAnimation = kAlwaysDismissedAnimation;
     }
   }
 
@@ -213,12 +213,12 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
   }
 
   void dispose() {
-    _performanceController.stop();
+    _controller.stop();
     super.dispose();
   }
 
   String get debugLabel => '$runtimeType';
-  String toString() => '$runtimeType(performance: $_performanceController)';
+  String toString() => '$runtimeType(animation: $_controller)';
 }
 
 class LocalHistoryEntry {
@@ -306,8 +306,8 @@ class _ModalScope extends StatefulComponent {
 class _ModalScopeState extends State<_ModalScope> {
   void initState() {
     super.initState();
-    config.route.performance?.addStatusListener(_performanceStatusChanged);
-    config.route.forwardPerformance?.addStatusListener(_performanceStatusChanged);
+    config.route.animation?.addStatusListener(_animationStatusChanged);
+    config.route.forwardAnimation?.addStatusListener(_animationStatusChanged);
   }
 
   void didUpdateConfig(_ModalScope oldConfig) {
@@ -315,12 +315,12 @@ class _ModalScopeState extends State<_ModalScope> {
   }
 
   void dispose() {
-    config.route.performance?.removeStatusListener(_performanceStatusChanged);
-    config.route.forwardPerformance?.removeStatusListener(_performanceStatusChanged);
+    config.route.animation?.removeStatusListener(_animationStatusChanged);
+    config.route.forwardAnimation?.removeStatusListener(_animationStatusChanged);
     super.dispose();
   }
 
-  void _performanceStatusChanged(PerformanceStatus status) {
+  void _animationStatusChanged(PerformanceStatus status) {
     setState(() {
       // The performances' states are our build state, and they changed already.
     });
@@ -333,7 +333,7 @@ class _ModalScopeState extends State<_ModalScope> {
       child: new _ModalScopeStatus(
         route: config.route,
         isCurrent: config.route.isCurrent,
-        child: config.route.buildPage(context, config.route.performance, config.route.forwardPerformance)
+        child: config.route.buildPage(context, config.route.animation, config.route.forwardAnimation)
       )
     );
     if (config.route.offstage) {
@@ -342,11 +342,11 @@ class _ModalScopeState extends State<_ModalScope> {
       contents = new Focus(
         key: new GlobalObjectKey(config.route),
         child: new IgnorePointer(
-          ignoring: config.route.performance?.status == PerformanceStatus.reverse,
+          ignoring: config.route.animation?.status == PerformanceStatus.reverse,
           child: config.route.buildTransitions(
             context,
-            config.route.performance,
-            config.route.forwardPerformance,
+            config.route.animation,
+            config.route.forwardAnimation,
             contents
           )
         )
@@ -396,8 +396,8 @@ abstract class ModalRoute<T> extends TransitionRoute<T> with LocalHistoryRoute<T
   // The API for subclasses to override - used by _ModalScope
 
   ModalPosition getPosition(BuildContext context) => null;
-  Widget buildPage(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance);
-  Widget buildTransitions(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance, Widget child) {
+  Widget buildPage(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation);
+  Widget buildTransitions(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation, Widget child) {
     return child;
   }
 
@@ -442,17 +442,23 @@ abstract class ModalRoute<T> extends TransitionRoute<T> with LocalHistoryRoute<T
     Widget barrier;
     if (barrierColor != null) {
       assert(barrierColor != _kTransparent);
+      Animated<Color> color = new ColorTween(
+        begin: _kTransparent,
+        end: barrierColor
+      ).animate(new CurvedAnimation(
+        parent: animation,
+        curve: Curves.ease
+      ));
       barrier = new AnimatedModalBarrier(
-        color: new AnimatedColorValue(_kTransparent, end: barrierColor, curve: Curves.ease),
-        performance: performance,
+        color: color,
         dismissable: barrierDismissable
       );
     } else {
       barrier = new ModalBarrier(dismissable: barrierDismissable);
     }
-    assert(performance.status != PerformanceStatus.dismissed);
+    assert(animation.status != PerformanceStatus.dismissed);
     return new IgnorePointer(
-      ignoring: performance.status == PerformanceStatus.reverse,
+      ignoring: animation.status == PerformanceStatus.reverse,
       child: barrier
     );
   }
@@ -470,7 +476,7 @@ abstract class ModalRoute<T> extends TransitionRoute<T> with LocalHistoryRoute<T
     _buildModalScope
   ];
 
-  String toString() => '$runtimeType($settings, performance: $_performance)';
+  String toString() => '$runtimeType($settings, animation: $_animation)';
 }
 
 /// A modal route that overlays a widget over the current route.

packages/flutter/lib/src/widgets/status_transitions.dart

@@ -9,12 +9,12 @@ import 'framework.dart';
 abstract class StatusTransitionComponent extends StatefulComponent {
   StatusTransitionComponent({
     Key key,
-    this.performance
+    this.animation
   }) : super(key: key) {
-    assert(performance != null);
+    assert(animation != null);
   }
 
-  final PerformanceView performance;
+  final Animated<double> animation;
 
   Widget build(BuildContext context);
 
@@ -24,18 +24,18 @@ abstract class StatusTransitionComponent extends StatefulComponent {
 class _StatusTransitionState extends State<StatusTransitionComponent> {
   void initState() {
     super.initState();
-    config.performance.addStatusListener(_performanceStatusChanged);
+    config.animation.addStatusListener(_performanceStatusChanged);
   }
 
   void didUpdateConfig(StatusTransitionComponent oldConfig) {
-    if (config.performance != oldConfig.performance) {
-      oldConfig.performance.removeStatusListener(_performanceStatusChanged);
-      config.performance.addStatusListener(_performanceStatusChanged);
+    if (config.animation != oldConfig.animation) {
+      oldConfig.animation.removeStatusListener(_performanceStatusChanged);
+      config.animation.addStatusListener(_performanceStatusChanged);
     }
   }
 
   void dispose() {
-    config.performance.removeStatusListener(_performanceStatusChanged);
+    config.animation.removeStatusListener(_performanceStatusChanged);
     super.dispose();
   }
 

packages/flutter/lib/src/widgets/transitions.dart

@@ -170,21 +170,19 @@ class ScaleTransition extends AnimatedComponent {
   }
 }
 
-class RotationTransition extends TransitionWithChild {
+class RotationTransition extends AnimatedComponent {
   RotationTransition({
     Key key,
-    this.turns,
-    PerformanceView performance,
-    Widget child
-  }) : super(key: key,
-             performance: performance,
-             child: child);
+    Animated<double> turns,
+    this.child
+  }) : turns = turns, super(key: key, animation: turns);
 
-  final AnimatedValue<double> turns;
+  final Animated<double> turns;
+  final Widget child;
 
-  Widget buildWithChild(BuildContext context, Widget child) {
-    performance.updateVariable(turns);
-    Matrix4 transform = new Matrix4.rotationZ(turns.value * math.PI * 2.0);
+  Widget build(BuildContext context) {
+    double turnsValue = turns.value;
+    Matrix4 transform = new Matrix4.rotationZ(turnsValue * math.PI * 2.0);
     return new Transform(
       transform: transform,
       alignment: const FractionalOffset(0.5, 0.5),
@@ -307,9 +305,9 @@ class AlignTransition extends TransitionWithChild {
 /// This class specializes the interpolation of AnimatedValue<RelativeRect> to
 /// be appropriate for rectangles that are described in terms of offsets from
 /// other rectangles.
-class AnimatedRelativeRectValue extends AnimatedValue<RelativeRect> {
-  AnimatedRelativeRectValue(RelativeRect begin, { RelativeRect end, Curve curve, Curve reverseCurve })
-    : super(begin, end: end, curve: curve, reverseCurve: reverseCurve);
+class RelativeRectTween extends Tween<RelativeRect> {
+  RelativeRectTween({ RelativeRect begin, RelativeRect end })
+    : super(begin: begin, end: end);
 
   RelativeRect lerp(double t) => RelativeRect.lerp(begin, end, t);
 }
@@ -320,22 +318,19 @@ class AnimatedRelativeRectValue extends AnimatedValue<RelativeRect> {
 /// of the performance.
 ///
 /// Only works if it's the child of a [Stack].
-class PositionedTransition extends TransitionWithChild {
+class PositionedTransition extends AnimatedComponent {
   PositionedTransition({
     Key key,
-    this.rect,
-    PerformanceView performance,
-    Widget child
-  }) : super(key: key,
-             performance: performance,
-             child: child) {
+    Animated<RelativeRect> rect,
+    this.child
+  }) : rect = rect, super(key: key, animation: rect) {
     assert(rect != null);
   }
 
-  final AnimatedRelativeRectValue rect;
+  final Animated<RelativeRect> rect;
+  final Widget child;
 
-  Widget buildWithChild(BuildContext context, Widget child) {
-    performance.updateVariable(rect);
+  Widget build(BuildContext context) {
     return new Positioned(
       top: rect.value.top,
       right: rect.value.right,

packages/flutter/test/widget/page_forward_transitions_test.dart

@@ -7,21 +7,22 @@ import 'package:flutter/animation.dart';
 import 'package:flutter/material.dart';
 import 'package:test/test.dart' hide TypeMatcher;
 
-class TestTransition extends TransitionComponent {
+class TestTransition extends AnimatedComponent {
   TestTransition({
     Key key,
     this.childFirstHalf,
     this.childSecondHalf,
-    PerformanceView performance
-  }) : super(key: key, performance: performance) {
-    assert(performance != null);
+    Animated<double> animation
+  }) : super(key: key, animation: animation) {
+    assert(animation != null);
   }
 
   final Widget childFirstHalf;
   final Widget childSecondHalf;
 
   Widget build(BuildContext context) {
-    if (performance.progress >= 0.5)
+    final Animated<double> animation = this.animation;
+    if (animation.value >= 0.5)
       return childSecondHalf;
     return childFirstHalf;
   }
@@ -32,7 +33,7 @@ class TestRoute<T> extends PageRoute<T> {
   final Widget child;
   Duration get transitionDuration => kMaterialPageRouteTransitionDuration;
   Color get barrierColor => null;
-  Widget buildPage(BuildContext context, PerformanceView performance, PerformanceView forwardPerformance) {
+  Widget buildPage(BuildContext context, Animated<double> animation, Animated<double> forwardAnimation) {
     return child;
   }
 }
@@ -81,12 +82,12 @@ void main() {
                           new TestTransition(
                             childFirstHalf: new Text('A'),
                             childSecondHalf: new Text('B'),
-                            performance: route.performance
+                            animation: route.animation
                           ),
                           new TestTransition(
                             childFirstHalf: new Text('C'),
                             childSecondHalf: new Text('D'),
-                            performance: route.forwardPerformance
+                            animation: route.forwardAnimation
                           ),
                         ]
                       );

packages/flutter/test/widget/positioned_test.dart

@@ -13,18 +13,17 @@ void main() {
   test('Can animate position data', () {
     testWidgets((WidgetTester tester) {
 
-      final AnimatedRelativeRectValue rect = new AnimatedRelativeRectValue(
-        new RelativeRect.fromRect(
+      final RelativeRectTween rect = new RelativeRectTween(
+        begin: new RelativeRect.fromRect(
           new Rect.fromLTRB(10.0, 20.0, 20.0, 30.0),
           new Rect.fromLTRB(0.0, 10.0, 100.0, 110.0)
         ),
         end: new RelativeRect.fromRect(
           new Rect.fromLTRB(80.0, 90.0, 90.0, 100.0),
           new Rect.fromLTRB(0.0, 10.0, 100.0, 110.0)
-        ),
-        curve: Curves.linear
+        )
       );
-      final Performance performance = new Performance(
+      final AnimationController controller = new AnimationController(
         duration: const Duration(seconds: 10)
       );
       final List<Size> sizes = <Size>[];
@@ -46,8 +45,7 @@ void main() {
             child: new Stack(
               children: <Widget>[
                 new PositionedTransition(
-                  rect: rect,
-                  performance: performance,
+                  rect: rect.animate(controller),
                   child: new Container(
                     key: key
                   )
@@ -58,7 +56,7 @@ void main() {
         )
       ); // t=0
       recordMetrics();
-      performance.play();
+      controller.forward();
       tester.pump(); // t=0 again
       recordMetrics();
       tester.pump(const Duration(seconds: 1)); // t=1