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// 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({
Key? key,
required this.animation,
}) : assert(animation != null),
super(key: key);
/// 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);
}
}