// 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:async'; import 'dart:ui' as ui show lerpDouble; import 'package:flutter/foundation.dart'; import 'package:flutter/physics.dart'; import 'package:flutter/scheduler.dart'; import 'animation.dart'; import 'curves.dart'; import 'listener_helpers.dart'; export 'package:flutter/scheduler.dart' show TickerFuture, TickerCanceled; // Examples can assume: // AnimationController _controller; /// The direction in which an animation is running. enum _AnimationDirection { /// The animation is running from beginning to end. forward, /// The animation is running backwards, from end to beginning. reverse, } final SpringDescription _kFlingSpringDescription = new SpringDescription.withDampingRatio( mass: 1.0, stiffness: 500.0, ratio: 1.0, ); const Tolerance _kFlingTolerance = const Tolerance( velocity: double.infinity, distance: 0.01, ); /// A controller for an animation. /// /// This class lets you perform tasks such as: /// /// * Play an animation [forward] or in [reverse], or [stop] an animation. /// * Set the animation to a specific [value]. /// * Define the [upperBound] and [lowerBound] values of an animation. /// * Create a [fling] animation effect using a physics simulation. /// /// By default, an [AnimationController] linearly produces values that range /// from 0.0 to 1.0, during a given duration. The animation controller generates /// a new value whenever the device running your app is ready to display a new /// frame (typically, this rate is around 60 values per second). /// /// An AnimationController needs a [TickerProvider], which is configured using /// the `vsync` argument on the constructor. If you are creating an /// AnimationController from a [State], then you can use the /// [TickerProviderStateMixin] and [SingleTickerProviderStateMixin] classes to /// obtain a suitable [TickerProvider]. The widget test framework [WidgetTester] /// object can be used as a ticker provider in the context of tests. In other /// contexts, you will have to either pass a [TickerProvider] from a higher /// level (e.g. indirectly from a [State] that mixes in /// [TickerProviderStateMixin]), or create a custom [TickerProvider] subclass. /// /// The methods that start animations return a [TickerFuture] object which /// completes when the animation completes successfully, and never throws an /// error; if the animation is canceled, the future never completes. This object /// also has a [TickerFuture.orCancel] property which returns a future that /// completes when the animation completes successfully, and completes with an /// error when the animation is aborted. /// /// This can be used to write code such as: /// /// ```dart /// Future<Null> fadeOutAndUpdateState() async { /// try { /// await fadeAnimationController.forward().orCancel; /// await sizeAnimationController.forward().orCancel; /// setState(() { /// dismissed = true; /// }); /// } on TickerCanceled { /// // the animation got canceled, probably because we were disposed /// } /// } /// ``` /// /// ...which asynchronously runs one animation, then runs another, then changes /// the state of the widget, without having to verify [State.mounted] is still /// true at each step, and without having to chain futures together explicitly. /// (This assumes that the controllers are created in [State.initState] and /// disposed in [State.dispose].) class AnimationController extends Animation<double> with AnimationEagerListenerMixin, AnimationLocalListenersMixin, AnimationLocalStatusListenersMixin { /// Creates an animation controller. /// /// * [value] is the initial value of the animation. If defaults to the lower /// bound. /// /// * [duration] is the length of time this animation should last. /// /// * [debugLabel] is a string to help identify this animation during /// debugging (used by [toString]). /// /// * [lowerBound] is the smallest value this animation can obtain and the /// value at which this animation is deemed to be dismissed. It cannot be /// null. /// /// * [upperBound] is the largest value this animation can obtain and the /// value at which this animation is deemed to be completed. It cannot be /// null. /// /// * `vsync` is the [TickerProvider] for the current context. It can be /// changed by calling [resync]. It is required and must not be null. See /// [TickerProvider] for advice on obtaining a ticker provider. AnimationController({ double value, this.duration, this.debugLabel, this.lowerBound: 0.0, this.upperBound: 1.0, @required TickerProvider vsync, }) : assert(lowerBound != null), assert(upperBound != null), assert(upperBound >= lowerBound), assert(vsync != null), _direction = _AnimationDirection.forward { _ticker = vsync.createTicker(_tick); _internalSetValue(value ?? lowerBound); } /// Creates an animation controller with no upper or lower bound for its value. /// /// * [value] is the initial value of the animation. /// /// * [duration] is the length of time this animation should last. /// /// * [debugLabel] is a string to help identify this animation during /// debugging (used by [toString]). /// /// * `vsync` is the [TickerProvider] for the current context. It can be /// changed by calling [resync]. It is required and must not be null. See /// [TickerProvider] for advice on obtaining a ticker provider. /// /// This constructor is most useful for animations that will be driven using a /// physics simulation, especially when the physics simulation has no /// pre-determined bounds. AnimationController.unbounded({ double value: 0.0, this.duration, this.debugLabel, @required TickerProvider vsync, }) : assert(value != null), assert(vsync != null), lowerBound = double.negativeInfinity, upperBound = double.infinity, _direction = _AnimationDirection.forward { _ticker = vsync.createTicker(_tick); _internalSetValue(value); } /// The value at which this animation is deemed to be dismissed. final double lowerBound; /// The value at which this animation is deemed to be completed. final double upperBound; /// A label that is used in the [toString] output. Intended to aid with /// identifying animation controller instances in debug output. final String debugLabel; /// Returns an [Animation<double>] for this animation controller, so that a /// pointer to this object can be passed around without allowing users of that /// pointer to mutate the [AnimationController] state. Animation<double> get view => this; /// The length of time this animation should last. Duration duration; Ticker _ticker; /// Recreates the [Ticker] with the new [TickerProvider]. void resync(TickerProvider vsync) { final Ticker oldTicker = _ticker; _ticker = vsync.createTicker(_tick); _ticker.absorbTicker(oldTicker); } Simulation _simulation; /// The current value of the animation. /// /// Setting this value notifies all the listeners that the value /// changed. /// /// Setting this value also stops the controller if it is currently /// running; if this happens, it also notifies all the status /// listeners. @override double get value => _value; double _value; /// Stops the animation controller and sets the current value of the /// animation. /// /// The new value is clamped to the range set by [lowerBound] and [upperBound]. /// /// Value listeners are notified even if this does not change the value. /// Status listeners are notified if the animation was previously playing. /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. /// /// See also: /// /// * [reset], which is equivalent to setting [value] to [lowerBound]. /// * [stop], which aborts the animation without changing its value or status /// and without dispatching any notifications other than completing or /// canceling the [TickerFuture]. /// * [forward], [reverse], [animateTo], [animateWith], [fling], and [repeat], /// which start the animation controller. set value(double newValue) { assert(newValue != null); stop(); _internalSetValue(newValue); notifyListeners(); _checkStatusChanged(); } /// Sets the controller's value to [lowerBound], stopping the animation (if /// in progress), and resetting to its beginning point, or dismissed state. /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. /// /// See also: /// /// * [value], which can be explicitly set to a specific value as desired. /// * [forward], which starts the animation in the forward direction. /// * [stop], which aborts the animation without changing its value or status /// and without dispatching any notifications other than completing or /// canceling the [TickerFuture]. void reset() { value = lowerBound; } /// The rate of change of [value] per second. /// /// If [isAnimating] is false, then [value] is not changing and the rate of /// change is zero. double get velocity { if (!isAnimating) return 0.0; return _simulation.dx(lastElapsedDuration.inMicroseconds.toDouble() / Duration.microsecondsPerSecond); } void _internalSetValue(double newValue) { _value = newValue.clamp(lowerBound, upperBound); if (_value == lowerBound) { _status = AnimationStatus.dismissed; } else if (_value == upperBound) { _status = AnimationStatus.completed; } else { _status = (_direction == _AnimationDirection.forward) ? AnimationStatus.forward : AnimationStatus.reverse; } } /// The amount of time that has passed between the time the animation started /// and the most recent tick of the animation. /// /// If the controller is not animating, the last elapsed duration is null. Duration get lastElapsedDuration => _lastElapsedDuration; Duration _lastElapsedDuration; /// Whether this animation is currently animating in either the forward or reverse direction. /// /// This is separate from whether it is actively ticking. An animation /// controller's ticker might get muted, in which case the animation /// controller's callbacks will no longer fire even though time is continuing /// to pass. See [Ticker.muted] and [TickerMode]. bool get isAnimating => _ticker != null && _ticker.isActive; _AnimationDirection _direction; @override AnimationStatus get status => _status; AnimationStatus _status; /// Starts running this animation forwards (towards the end). /// /// Returns a [TickerFuture] that completes when the animation is complete. /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. /// /// During the animation, [status] is reported as [AnimationStatus.forward], /// which switches to [AnimationStatus.completed] when [upperBound] is /// reached at the end of the animation. TickerFuture forward({ double from }) { assert(() { if (duration == null) { throw new FlutterError( 'AnimationController.forward() called with no default Duration.\n' 'The "duration" property should be set, either in the constructor or later, before ' 'calling the forward() function.' ); } return true; }()); _direction = _AnimationDirection.forward; if (from != null) value = from; return _animateToInternal(upperBound); } /// Starts running this animation in reverse (towards the beginning). /// /// Returns a [TickerFuture] that completes when the animation is dismissed. /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. /// /// During the animation, [status] is reported as [AnimationStatus.reverse], /// which switches to [AnimationStatus.dismissed] when [lowerBound] is /// reached at the end of the animation. TickerFuture reverse({ double from }) { assert(() { if (duration == null) { throw new FlutterError( 'AnimationController.reverse() called with no default Duration.\n' 'The "duration" property should be set, either in the constructor or later, before ' 'calling the reverse() function.' ); } return true; }()); _direction = _AnimationDirection.reverse; if (from != null) value = from; return _animateToInternal(lowerBound); } /// Drives the animation from its current value to target. /// /// Returns a [TickerFuture] that completes when the animation is complete. /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. /// /// During the animation, [status] is reported as [AnimationStatus.forward] /// regardless of whether `target` > [value] or not. At the end of the /// animation, when `target` is reached, [status] is reported as /// [AnimationStatus.completed]. TickerFuture animateTo(double target, { Duration duration, Curve curve: Curves.linear }) { _direction = _AnimationDirection.forward; return _animateToInternal(target, duration: duration, curve: curve); } TickerFuture _animateToInternal(double target, { Duration duration, Curve curve: Curves.linear }) { Duration simulationDuration = duration; if (simulationDuration == null) { assert(() { if (this.duration == null) { throw new FlutterError( 'AnimationController.animateTo() called with no explicit Duration and no default Duration.\n' 'Either the "duration" argument to the animateTo() method should be provided, or the ' '"duration" property should be set, either in the constructor or later, before ' 'calling the animateTo() function.' ); } return true; }()); final double range = upperBound - lowerBound; final double remainingFraction = range.isFinite ? (target - _value).abs() / range : 1.0; simulationDuration = this.duration * remainingFraction; } else if (target == value) { // Already at target, don't animate. simulationDuration = Duration.zero; } stop(); if (simulationDuration == Duration.zero) { if (value != target) { _value = target.clamp(lowerBound, upperBound); notifyListeners(); } _status = (_direction == _AnimationDirection.forward) ? AnimationStatus.completed : AnimationStatus.dismissed; _checkStatusChanged(); return new TickerFuture.complete(); } assert(simulationDuration > Duration.zero); assert(!isAnimating); return _startSimulation(new _InterpolationSimulation(_value, target, simulationDuration, curve)); } /// Starts running this animation in the forward direction, and /// restarts the animation when it completes. /// /// Defaults to repeating between the lower and upper bounds. /// /// Returns a [TickerFuture] that never completes. The [TickerFuture.orCancel] future /// completes with an error when the animation is stopped (e.g. with [stop]). /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. TickerFuture repeat({ double min, double max, Duration period }) { min ??= lowerBound; max ??= upperBound; period ??= duration; assert(() { if (period == null) { throw new FlutterError( 'AnimationController.repeat() called without an explicit period and with no default Duration.\n' 'Either the "period" argument to the repeat() method should be provided, or the ' '"duration" property should be set, either in the constructor or later, before ' 'calling the repeat() function.' ); } return true; }()); return animateWith(new _RepeatingSimulation(min, max, period)); } /// Drives the animation with a critically damped spring (within [lowerBound] /// and [upperBound]) and initial velocity. /// /// If velocity is positive, the animation will complete, otherwise it will /// dismiss. /// /// Returns a [TickerFuture] that completes when the animation is complete. /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. TickerFuture fling({ double velocity: 1.0 }) { _direction = velocity < 0.0 ? _AnimationDirection.reverse : _AnimationDirection.forward; final double target = velocity < 0.0 ? lowerBound - _kFlingTolerance.distance : upperBound + _kFlingTolerance.distance; final Simulation simulation = new SpringSimulation(_kFlingSpringDescription, value, target, velocity) ..tolerance = _kFlingTolerance; return animateWith(simulation); } /// Drives the animation according to the given simulation. /// /// Returns a [TickerFuture] that completes when the animation is complete. /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. TickerFuture animateWith(Simulation simulation) { stop(); return _startSimulation(simulation); } TickerFuture _startSimulation(Simulation simulation) { assert(simulation != null); assert(!isAnimating); _simulation = simulation; _lastElapsedDuration = Duration.zero; _value = simulation.x(0.0).clamp(lowerBound, upperBound); final Future<Null> result = _ticker.start(); _status = (_direction == _AnimationDirection.forward) ? AnimationStatus.forward : AnimationStatus.reverse; _checkStatusChanged(); return result; } /// Stops running this animation. /// /// This does not trigger any notifications. The animation stops in its /// current state. /// /// By default, the most recently returned [TickerFuture] is marked as having /// been canceled, meaning the future never completes and its /// [TickerFuture.orCancel] derivative future completes with a [TickerCanceled] /// error. By passing the `canceled` argument with the value false, this is /// reversed, and the futures complete successfully. /// /// See also: /// /// * [reset], which stops the animation and resets it to the [lowerBound], /// and which does send notifications. /// * [forward], [reverse], [animateTo], [animateWith], [fling], and [repeat], /// which restart the animation controller. void stop({ bool canceled: true }) { _simulation = null; _lastElapsedDuration = null; _ticker.stop(canceled: canceled); } /// Release the resources used by this object. The object is no longer usable /// after this method is called. /// /// The most recently returned [TickerFuture], if any, is marked as having been /// canceled, meaning the future never completes and its [TickerFuture.orCancel] /// derivative future completes with a [TickerCanceled] error. @override void dispose() { assert(() { if (_ticker == null) { throw new FlutterError( 'AnimationController.dispose() called more than once.\n' 'A given $runtimeType cannot be disposed more than once.\n' 'The following $runtimeType object was disposed multiple times:\n' ' $this' ); } return true; }()); _ticker.dispose(); _ticker = null; super.dispose(); } AnimationStatus _lastReportedStatus = AnimationStatus.dismissed; void _checkStatusChanged() { final AnimationStatus newStatus = status; if (_lastReportedStatus != newStatus) { _lastReportedStatus = newStatus; notifyStatusListeners(newStatus); } } void _tick(Duration elapsed) { _lastElapsedDuration = elapsed; final double elapsedInSeconds = elapsed.inMicroseconds.toDouble() / Duration.microsecondsPerSecond; assert(elapsedInSeconds >= 0.0); _value = _simulation.x(elapsedInSeconds).clamp(lowerBound, upperBound); if (_simulation.isDone(elapsedInSeconds)) { _status = (_direction == _AnimationDirection.forward) ? AnimationStatus.completed : AnimationStatus.dismissed; stop(canceled: false); } notifyListeners(); _checkStatusChanged(); } @override String toStringDetails() { final String paused = isAnimating ? '' : '; paused'; final String ticker = _ticker == null ? '; DISPOSED' : (_ticker.muted ? '; silenced' : ''); final String label = debugLabel == null ? '' : '; for $debugLabel'; final String more = '${super.toStringDetails()} ${value.toStringAsFixed(3)}'; return '$more$paused$ticker$label'; } } class _InterpolationSimulation extends Simulation { _InterpolationSimulation(this._begin, this._end, Duration duration, this._curve) : assert(_begin != null), assert(_end != null), assert(duration != null && duration.inMicroseconds > 0), _durationInSeconds = duration.inMicroseconds / Duration.microsecondsPerSecond; final double _durationInSeconds; final double _begin; final double _end; final Curve _curve; @override double x(double timeInSeconds) { final double t = (timeInSeconds / _durationInSeconds).clamp(0.0, 1.0); if (t == 0.0) return _begin; else if (t == 1.0) return _end; else return _begin + (_end - _begin) * _curve.transform(t); } @override double dx(double timeInSeconds) { final double epsilon = tolerance.time; return (x(timeInSeconds + epsilon) - x(timeInSeconds - epsilon)) / (2 * epsilon); } @override bool isDone(double timeInSeconds) => timeInSeconds > _durationInSeconds; } class _RepeatingSimulation extends Simulation { _RepeatingSimulation(this.min, this.max, Duration period) : _periodInSeconds = period.inMicroseconds / Duration.microsecondsPerSecond { assert(_periodInSeconds > 0.0); } final double min; final double max; final double _periodInSeconds; @override double x(double timeInSeconds) { assert(timeInSeconds >= 0.0); final double t = (timeInSeconds / _periodInSeconds) % 1.0; return ui.lerpDouble(min, max, t); } @override double dx(double timeInSeconds) => (max - min) / _periodInSeconds; @override bool isDone(double timeInSeconds) => false; }