1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
// Copyright 2015 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 'package:flutter/foundation.dart';
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.
StatusTransitionWidget({
Key key,
@required this.animation
}) : super(key: key) {
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
_StatusTransitionState createState() => new _StatusTransitionState();
}
class _StatusTransitionState extends State<StatusTransitionWidget> {
@override
void initState() {
super.initState();
config.animation.addStatusListener(_animationStatusChanged);
}
@override
void didUpdateConfig(StatusTransitionWidget oldConfig) {
if (config.animation != oldConfig.animation) {
oldConfig.animation.removeStatusListener(_animationStatusChanged);
config.animation.addStatusListener(_animationStatusChanged);
}
}
@override
void dispose() {
config.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 config.build(context);
}
}