Merge pull request #2934 from Hixie/toStringAnimation

toStrings for Animations and Animatables

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

@@ -28,6 +28,9 @@ class _AlwaysCompleteAnimation extends Animation<double> {
 
   @override
   double get value => 1.0;
+
+  @override
+  String toString() => 'kAlwaysCompleteAnimation';
 }
 
 /// An animation that is always complete.
@@ -57,6 +60,9 @@ class _AlwaysDismissedAnimation extends Animation<double> {
 
   @override
   double get value => 0.0;
+
+  @override
+  String toString() => 'kAlwaysDismissedAnimation';
 }
 
 /// An animation that is always dismissed.
@@ -96,6 +102,11 @@ class AlwaysStoppedAnimation<T> extends Animation<T> {
 
   @override
   AnimationStatus get status => AnimationStatus.forward;
+
+  @override
+  String toStringDetails() {
+    return '${super.toStringDetails()} $value; paused';
+  }
 }
 
 /// Implements most of the [Animation] interface, by deferring its behavior to a
@@ -195,6 +206,13 @@ class ProxyAnimation extends Animation<double>
 
   @override
   double get value => _parent != null ? _parent.value : _value;
+
+  @override
+  String toString() {
+    if (parent == null)
+      return '$runtimeType(null; ${super.toStringDetails()} ${value.toStringAsFixed(3)})';
+    return '$parent\u27A9$runtimeType';
+  }
 }
 
 /// An animation that is the reverse of another animation.
@@ -251,6 +269,11 @@ class ReverseAnimation extends Animation<double>
       case AnimationStatus.dismissed: return AnimationStatus.completed;
     }
   }
+
+  @override
+  String toString() {
+    return '$parent\u27AA$runtimeType';
+  }
 }
 
 /// An animation that applies a curve to another animation.
@@ -317,10 +340,13 @@ class CurvedAnimation extends Animation<double> with AnimationWithParentMixin<do
     }
   }
 
+  bool get _useForwardCurve {
+    return reverseCurve == null || (_curveDirection ?? parent.status) != AnimationStatus.reverse;
+  }
+
   @override
   double get value {
-    final bool useForwardCurve = reverseCurve == null || (_curveDirection ?? parent.status) != AnimationStatus.reverse;
-    Curve activeCurve = useForwardCurve ? curve : reverseCurve;
+    Curve activeCurve = _useForwardCurve ? curve : reverseCurve;
 
     double t = parent.value;
     if (activeCurve == null)
@@ -331,6 +357,15 @@ class CurvedAnimation extends Animation<double> with AnimationWithParentMixin<do
     }
     return activeCurve.transform(t);
   }
+
+  @override
+  String toString() {
+    if (reverseCurve == null)
+      return '$parent\u27A9$curve';
+    if (_useForwardCurve) 
+     return '$parent\u27A9$curve\u2092\u2099/$reverseCurve';
+    return '$parent\u27A9$curve/$reverseCurve\u2092\u2099';
+  }
 }
 
 enum _TrainHoppingMode { minimize, maximize }
@@ -439,4 +474,11 @@ class TrainHoppingAnimation extends Animation<double>
       _nextTrain = null;
     }
   }
+
+  @override
+  String toString() {
+    if (_nextTrain != null)
+      return '$currentTrain\u27A9$runtimeType(next: $_nextTrain)';
+    return '$currentTrain\u27A9$runtimeType(no next)';
+  }
 }

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

@@ -28,6 +28,11 @@ abstract class Curve {
   /// Returns a new curve that is the reversed inversion of this one.
   /// This is often useful as the reverseCurve of an [Animation].
   Curve get flipped => new FlippedCurve(this);
+
+  @override
+  String toString() {
+    return '$runtimeType';
+  }
 }
 
 /// The identity map over the unit interval.
@@ -49,6 +54,11 @@ class SawTooth extends Curve {
     t *= count;
     return t - t.truncateToDouble();
   }
+
+  @override
+  String toString() {
+    return '$runtimeType($count)';
+  }
 }
 
 /// A curve that is 0.0 until start, then curved from 0.0 to 1.0 at end, then 1.0.
@@ -76,6 +86,13 @@ class Interval extends Curve {
       return t;
     return curve.transform(t);
   }
+
+  @override
+  String toString() {
+    if (curve is! Linear)
+      return '$runtimeType($start\u22EF$end)\u27A9$curve';
+    return '$runtimeType($start\u22EF$end)';
+  }
 }
 
 /// A cubic polynomial mapping of the unit interval.
@@ -102,6 +119,11 @@ class Cubic extends Curve {
         end = midpoint;
     }
   }
+
+  @override
+  String toString() {
+    return '$runtimeType(${a.toStringAsFixed(2)}, ${b.toStringAsFixed(2)}, ${c.toStringAsFixed(2)}, ${d.toStringAsFixed(2)})';
+  }
 }
 
 double _bounce(double t) {
@@ -126,6 +148,11 @@ class FlippedCurve extends Curve {
 
   @override
   double transform(double t) => 1.0 - curve.transform(1.0 - t);
+
+  @override
+  String toString() {
+    return '$runtimeType($curve)';
+  }
 }
 
 /// An oscillating curve that grows in magnitude.
@@ -173,6 +200,11 @@ class ElasticInCurve extends Curve {
     t = t - 1.0;
     return -math.pow(2.0, 10.0 * t) * math.sin((t - s) * (math.PI * 2.0) / period);
   }
+
+  @override
+  String toString() {
+    return '$runtimeType($period)';
+  }
 }
 
 /// An oscillating curve that shrinks in magnitude while overshooting its bounds.
@@ -186,6 +218,11 @@ class ElasticOutCurve extends Curve {
     double s = period / 4.0;
     return math.pow(2.0, -10 * t) * math.sin((t - s) * (math.PI * 2.0) / period) + 1.0;
   }
+
+  @override
+  String toString() {
+    return '$runtimeType($period)';
+  }
 }
 
 /// An oscillating curve that grows and then shrinks in magnitude while overshooting its bounds.
@@ -203,6 +240,11 @@ class ElasticInOutCurve extends Curve {
     else
       return math.pow(2.0, -10.0 * t) * math.sin((t - s) * (math.PI * 2.0) / period) * 0.5 + 1.0;
   }
+
+  @override
+  String toString() {
+    return '$runtimeType($period)';
+  }
 }
 
 /// A collection of common animation curves.

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

@@ -33,7 +33,6 @@ abstract class Animatable<T> {
 class _AnimatedEvaluation<T> extends Animation<T> with AnimationWithParentMixin<double> {
   _AnimatedEvaluation(this.parent, this._evaluatable);
 
-  /// The animation from which this value is derived.
   @override
   final Animation<double> parent;
 
@@ -41,6 +40,16 @@ class _AnimatedEvaluation<T> extends Animation<T> with AnimationWithParentMixin<
 
   @override
   T get value => _evaluatable.evaluate(parent);
+
+  @override
+  String toString() {
+    return '$parent\u27A9$_evaluatable';
+  }
+
+  @override
+  String toStringDetails() {
+    return '${super.toStringDetails()} $_evaluatable';
+  }
 }
 
 class _ChainedEvaluation<T> extends Animatable<T> {
@@ -54,6 +63,11 @@ class _ChainedEvaluation<T> extends Animatable<T> {
     double value = _parent.evaluate(animation);
     return _evaluatable.evaluate(new AlwaysStoppedAnimation<double>(value));
   }
+
+  @override
+  String toString() {
+    return '$_parent\u27A9$_evaluatable';
+  }
 }
 
 /// A linear interpolation between a beginning and ending value.