90 lines
2.8 KiB
Dart
90 lines
2.8 KiB
Dart
// Copyright 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'dart:ui' show Color, Size, Rect, VoidCallback;
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/// The status of an animation
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enum AnimationStatus {
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/// The animation is stopped at the beginning
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dismissed,
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/// The animation is running from beginning to end
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forward,
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/// The animation is running backwards, from end to beginning
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reverse,
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/// The animation is stopped at the end
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completed,
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}
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typedef void AnimationStatusListener(AnimationStatus status);
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/// An animation with a value of type T
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///
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/// An animation consists of a value (of type T) together with a status. The
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/// status indicates whether the animation is conceptually running from
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/// beginning to end or from the end back to the beginning, although the actual
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/// value of the animation might not change monotonically (e.g., if the
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/// animation uses a curve that bounces).
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///
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/// Animations also let other objects listen for changes to either their value
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/// or their status. These callbacks are called during the "animation" phase of
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/// the pipeline, just prior to rebuilding widgets.
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///
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/// To create a new animation that you can run forward and backward, consider
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/// using [AnimationController].
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abstract class Animation<T> {
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const Animation();
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/// Calls the listener every time the value of the animation changes.
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void addListener(VoidCallback listener);
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/// Stop calling the listener every time the value of the animation changes.
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void removeListener(VoidCallback listener);
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/// Calls listener every time the status of the animation changes.
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void addStatusListener(AnimationStatusListener listener);
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/// Stops calling the listener every time the status of the animation changes.
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void removeStatusListener(AnimationStatusListener listener);
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/// The current status of this animation.
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AnimationStatus get status;
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/// The current value of the animation.
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T get value;
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/// Whether this animation is stopped at the beginning.
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bool get isDismissed => status == AnimationStatus.dismissed;
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/// Whether this animation is stopped at the end.
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bool get isCompleted => status == AnimationStatus.completed;
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@override
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String toString() {
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return '$runtimeType(${toStringDetails()})';
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}
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String toStringDetails() {
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assert(status != null);
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String icon;
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switch (status) {
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case AnimationStatus.forward:
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icon = '\u25B6'; // >
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break;
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case AnimationStatus.reverse:
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icon = '\u25C0'; // <
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break;
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case AnimationStatus.completed:
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icon = '\u23ED'; // >>|
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break;
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case AnimationStatus.dismissed:
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icon = '\u23EE'; // |<<
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break;
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}
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assert(icon != null);
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return '$icon';
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}
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}
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