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