Adding onEnd callback to implicit animated widgets (#38979)

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

@@ -227,10 +227,11 @@ class AnimatedTheme extends ImplicitlyAnimatedWidget {
     this.isMaterialAppTheme = false,
     Curve curve = Curves.linear,
     Duration duration = kThemeAnimationDuration,
+    VoidCallback onEnd,
     @required this.child,
   }) : assert(child != null),
        assert(data != null),
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// Specifies the color and typography values for descendant widgets.
   final ThemeData data;

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

@@ -276,6 +276,7 @@ abstract class ImplicitlyAnimatedWidget extends StatefulWidget {
     Key key,
     this.curve = Curves.linear,
     @required this.duration,
+    this.onEnd,
   }) : assert(curve != null),
        assert(duration != null),
        super(key: key);
@@ -286,6 +287,12 @@ abstract class ImplicitlyAnimatedWidget extends StatefulWidget {
   /// The duration over which to animate the parameters of this container.
   final Duration duration;
 
+  /// Called every time an animation completes.
+  ///
+  /// This can be useful to trigger additional actions (e.g. another animation)
+  /// at the end of the current animation.
+  final VoidCallback onEnd;
+
   @override
   ImplicitlyAnimatedWidgetState<ImplicitlyAnimatedWidget> createState();
 
@@ -356,6 +363,17 @@ abstract class ImplicitlyAnimatedWidgetState<T extends ImplicitlyAnimatedWidget>
       debugLabel: kDebugMode ? '${widget.toStringShort()}' : null,
       vsync: this,
     );
+    _controller.addStatusListener((AnimationStatus status) {
+      switch (status) {
+        case AnimationStatus.completed:
+          if (widget.onEnd != null)
+            widget.onEnd();
+          break;
+        case AnimationStatus.dismissed:
+        case AnimationStatus.forward:
+        case AnimationStatus.reverse:
+      }
+    });
     _updateCurve();
     _constructTweens();
     didUpdateTweens();
@@ -624,6 +642,7 @@ class AnimatedContainer extends ImplicitlyAnimatedWidget {
     this.child,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
   }) : assert(margin == null || margin.isNonNegative),
        assert(padding == null || padding.isNonNegative),
        assert(decoration == null || decoration.debugAssertIsValid()),
@@ -638,7 +657,7 @@ class AnimatedContainer extends ImplicitlyAnimatedWidget {
           ? constraints?.tighten(width: width, height: height)
             ?? BoxConstraints.tightFor(width: width, height: height)
           : constraints,
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// The [child] contained by the container.
   ///
@@ -780,9 +799,10 @@ class AnimatedPadding extends ImplicitlyAnimatedWidget {
     this.child,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
   }) : assert(padding != null),
        assert(padding.isNonNegative),
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// The amount of space by which to inset the child.
   final EdgeInsetsGeometry padding;
@@ -859,8 +879,9 @@ class AnimatedAlign extends ImplicitlyAnimatedWidget {
     this.child,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
   }) : assert(alignment != null),
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// How to align the child.
   ///
@@ -967,9 +988,10 @@ class AnimatedPositioned extends ImplicitlyAnimatedWidget {
     this.height,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
   }) : assert(left == null || right == null || width == null),
        assert(top == null || bottom == null || height == null),
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// Creates a widget that animates the rectangle it occupies implicitly.
   ///
@@ -980,13 +1002,14 @@ class AnimatedPositioned extends ImplicitlyAnimatedWidget {
     Rect rect,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
   }) : left = rect.left,
        top = rect.top,
        width = rect.width,
        height = rect.height,
        right = null,
        bottom = null,
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// The widget below this widget in the tree.
   ///
@@ -1118,9 +1141,10 @@ class AnimatedPositionedDirectional extends ImplicitlyAnimatedWidget {
     this.height,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
   }) : assert(start == null || end == null || width == null),
        assert(top == null || bottom == null || height == null),
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// The widget below this widget in the tree.
   ///
@@ -1274,9 +1298,10 @@ class AnimatedOpacity extends ImplicitlyAnimatedWidget {
     @required this.opacity,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
     this.alwaysIncludeSemantics = false,
   }) : assert(opacity != null && opacity >= 0.0 && opacity <= 1.0),
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// The widget below this widget in the tree.
   ///
@@ -1369,12 +1394,13 @@ class AnimatedDefaultTextStyle extends ImplicitlyAnimatedWidget {
     this.maxLines,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
   }) : assert(style != null),
        assert(child != null),
        assert(softWrap != null),
        assert(overflow != null),
        assert(maxLines == null || maxLines > 0),
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// The widget below this widget in the tree.
   ///
@@ -1484,6 +1510,7 @@ class AnimatedPhysicalModel extends ImplicitlyAnimatedWidget {
     this.animateShadowColor = true,
     Curve curve = Curves.linear,
     @required Duration duration,
+    VoidCallback onEnd,
   }) : assert(child != null),
        assert(shape != null),
        assert(clipBehavior != null),
@@ -1493,7 +1520,7 @@ class AnimatedPhysicalModel extends ImplicitlyAnimatedWidget {
        assert(shadowColor != null),
        assert(animateColor != null),
        assert(animateShadowColor != null),
-       super(key: key, curve: curve, duration: duration);
+       super(key: key, curve: curve, duration: duration, onEnd: onEnd);
 
   /// The widget below this widget in the tree.
   ///

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

@@ -127,12 +127,12 @@ class TweenAnimationBuilder<T> extends ImplicitlyAnimatedWidget {
     @required Duration duration,
     Curve curve = Curves.linear,
     @required this.builder,
-    this.onEnd,
+    VoidCallback onEnd,
     this.child,
   }) : assert(tween != null),
        assert(curve != null),
        assert(builder != null),
-       super(key: key, duration: duration, curve: curve);
+       super(key: key, duration: duration, curve: curve, onEnd: onEnd);
 
   /// Defines the target value for the animation.
   ///
@@ -186,12 +186,6 @@ class TweenAnimationBuilder<T> extends ImplicitlyAnimatedWidget {
   /// performance significantly in some cases and is therefore a good practice.
   final Widget child;
 
-  /// Called every time an animation completes.
-  ///
-  /// This can be useful to trigger additional actions (e.g. another animation)
-  /// at the end of the current animation.
-  final VoidCallback onEnd;
-
   @override
   ImplicitlyAnimatedWidgetState<ImplicitlyAnimatedWidget> createState() {
     return _TweenAnimationBuilderState<T>();
@@ -206,27 +200,11 @@ class _TweenAnimationBuilderState<T> extends AnimatedWidgetBaseState<TweenAnimat
     _currentTween = widget.tween;
     _currentTween.begin ??= _currentTween.end;
     super.initState();
-    // The statusListener is removed when the superclass disposes the controller.
-    controller.addStatusListener(_onAnimationStatusChanged);
     if (_currentTween.begin != _currentTween.end) {
       controller.forward();
     }
   }
 
-  void _onAnimationStatusChanged(AnimationStatus status) {
-    switch (status) {
-      case AnimationStatus.dismissed:
-      case AnimationStatus.forward:
-      case AnimationStatus.reverse:
-        break;
-      case AnimationStatus.completed:
-        if (widget.onEnd != null) {
-          widget.onEnd();
-        }
-        break;
-    }
-  }
-
   @override
   void forEachTween(TweenVisitor<dynamic> visitor) {
     assert(