| // Copyright 2014 The Flutter 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 'basic.dart'; |
| import 'framework.dart'; |
| |
| /// A widget that rebuilds when the given animation changes status. |
| abstract class StatusTransitionWidget extends StatefulWidget { |
| /// Initializes fields for subclasses. |
| /// |
| /// The [animation] argument must not be null. |
| const StatusTransitionWidget({ |
| super.key, |
| required this.animation, |
| }) : assert(animation != null); |
| |
| /// The animation to which this widget is listening. |
| final Animation<double> animation; |
| |
| /// Override this method to build widgets that depend on the current status |
| /// of the animation. |
| Widget build(BuildContext context); |
| |
| @override |
| State<StatusTransitionWidget> createState() => _StatusTransitionState(); |
| } |
| |
| class _StatusTransitionState extends State<StatusTransitionWidget> { |
| @override |
| void initState() { |
| super.initState(); |
| widget.animation.addStatusListener(_animationStatusChanged); |
| } |
| |
| @override |
| void didUpdateWidget(StatusTransitionWidget oldWidget) { |
| super.didUpdateWidget(oldWidget); |
| if (widget.animation != oldWidget.animation) { |
| oldWidget.animation.removeStatusListener(_animationStatusChanged); |
| widget.animation.addStatusListener(_animationStatusChanged); |
| } |
| } |
| |
| @override |
| void dispose() { |
| widget.animation.removeStatusListener(_animationStatusChanged); |
| super.dispose(); |
| } |
| |
| void _animationStatusChanged(AnimationStatus status) { |
| setState(() { |
| // The animation's state is our build state, and it changed already. |
| }); |
| } |
| |
| @override |
| Widget build(BuildContext context) { |
| return widget.build(context); |
| } |
| } |