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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<double> _controller = new StreamController<double>.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 // TODO(ianh): Rename this to valueStream once we've landed the fn2 fork | |
27 Stream<double> get onValueChanged => _controller.stream; | |
28 | |
29 double get value => _value; | |
30 | |
31 void set value(double value) { | |
32 stop(); | |
33 _setValue(value); | |
34 } | |
35 | |
36 bool get isAnimating => _animation != null; | |
37 | |
38 void _setValue(double value) { | |
39 _value = value; | |
40 _controller.add(_value); | |
41 if (_onChange != null) | |
42 _onChange(); | |
43 } | |
44 | |
45 void _done() { | |
46 _animation = null; | |
47 if (_completer == null) | |
48 return; | |
49 Completer completer = _completer; | |
50 _completer = null; | |
51 completer.complete(_value); | |
52 } | |
53 | |
54 void stop() { | |
55 if (_animation != null) { | |
56 _animation.cancel(); // will call _done() if it isn't already finished | |
57 _done(); | |
58 } | |
59 } | |
60 | |
61 Future<double> animateTo(double newValue, double duration, | |
62 { Curve curve: linear, double initialDelay: 0.0 }) { | |
63 stop(); | |
64 | |
65 _animation = new AnimationGenerator( | |
66 duration: duration, | |
67 begin: _value, | |
68 end: newValue, | |
69 curve: curve, | |
70 initialDelay: initialDelay) | |
71 ..onTick.listen(_setValue, onDone: _done); | |
72 | |
73 _completer = new Completer(); | |
74 return _completer.future; | |
75 } | |
76 | |
77 double get remainingTime { | |
78 if (_animation == null) | |
79 return 0.0; | |
80 return _animation.remainingTime; | |
81 } | |
82 | |
83 } | |
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