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1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 import 'curves.dart'; | |
6 import 'dart:async'; | |
7 import 'generators.dart'; | |
8 | |
9 typedef void Callback (); | |
10 | |
11 class AnimatedValue { | |
12 StreamController _controller = new StreamController.broadcast(sync: true); | |
13 AnimationGenerator _animation; | |
14 Completer _completer; | |
15 double _value; | |
16 | |
17 AnimatedValue(double initial, { Callback onChange }) { | |
18 _value = initial; | |
19 _onChange = onChange; | |
20 } | |
21 Callback _onChange; | |
22 | |
23 // A stream of change in value from |initial|. The stream does not | |
24 // contain the initial value. Consumers should check the initial value via | |
25 // the |value| accessor. | |
26 Stream<double> get onValueChanged => _controller.stream; | |
27 | |
28 double get value => _value; | |
29 | |
30 void set value(double value) { | |
31 stop(); | |
32 _setValue(value); | |
33 } | |
34 | |
35 bool get isAnimating => _animation != null; | |
36 | |
37 void _setValue(double value) { | |
38 _value = value; | |
39 _controller.add(_value); | |
40 if (_onChange != null) | |
41 _onChange(); | |
42 } | |
43 | |
44 void _done() { | |
45 _animation = null; | |
46 if (_completer == null) | |
47 return; | |
48 Completer completer = _completer; | |
49 _completer = null; | |
50 completer.complete(_value); | |
51 } | |
52 | |
53 void stop() { | |
54 if (_animation != null) { | |
55 _animation.cancel(); // will call _done() if it isn't already finished | |
56 _done(); | |
57 } | |
58 } | |
59 | |
60 Future<double> animateTo(double newValue, double duration, | |
61 { Curve curve: linear, double initialDelay: 0.0 }) { | |
62 stop(); | |
63 | |
64 _animation = new AnimationGenerator( | |
65 duration: duration, | |
66 begin: _value, | |
67 end: newValue, | |
68 curve: curve, | |
69 initialDelay: initialDelay) | |
70 ..onTick.listen(_setValue, onDone: _done); | |
71 | |
72 _completer = new Completer(); | |
73 return _completer.future; | |
74 } | |
75 | |
76 double get remainingTime { | |
77 if (_animation == null) | |
78 return 0.0; | |
79 return _animation.remainingTime; | |
80 } | |
81 | |
82 } | |
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