| // Copyright 2014 The Flutter 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 'package:flutter/foundation.dart'; |
| |
| import 'animation.dart'; |
| |
| /// A mixin that helps listen to another object only when this object has registered listeners. |
| /// |
| /// This mixin provides implementations of [didRegisterListener] and [didUnregisterListener], |
| /// and therefore can be used in conjunction with mixins that require these methods, |
| /// [AnimationLocalListenersMixin] and [AnimationLocalStatusListenersMixin]. |
| mixin AnimationLazyListenerMixin { |
| int _listenerCounter = 0; |
| |
| /// Calls [didStartListening] every time a registration of a listener causes |
| /// an empty list of listeners to become non-empty. |
| /// |
| /// See also: |
| /// |
| /// * [didUnregisterListener], which may cause the listener list to |
| /// become empty again, and in turn cause this method to call |
| /// [didStartListening] again. |
| void didRegisterListener() { |
| assert(_listenerCounter >= 0); |
| if (_listenerCounter == 0) |
| didStartListening(); |
| _listenerCounter += 1; |
| } |
| |
| /// Calls [didStopListening] when an only remaining listener is unregistered, |
| /// thus making the list empty. |
| /// |
| /// See also: |
| /// |
| /// * [didRegisterListener], which causes the listener list to become non-empty. |
| void didUnregisterListener() { |
| assert(_listenerCounter >= 1); |
| _listenerCounter -= 1; |
| if (_listenerCounter == 0) |
| didStopListening(); |
| } |
| |
| /// Called when the number of listeners changes from zero to one. |
| @protected |
| void didStartListening(); |
| |
| /// Called when the number of listeners changes from one to zero. |
| @protected |
| void didStopListening(); |
| |
| /// Whether there are any listeners. |
| bool get isListening => _listenerCounter > 0; |
| } |
| |
| /// A mixin that replaces the [didRegisterListener]/[didUnregisterListener] contract |
| /// with a dispose contract. |
| /// |
| /// This mixin provides implementations of [didRegisterListener] and [didUnregisterListener], |
| /// and therefore can be used in conjunction with mixins that require these methods, |
| /// [AnimationLocalListenersMixin] and [AnimationLocalStatusListenersMixin]. |
| mixin AnimationEagerListenerMixin { |
| /// This implementation ignores listener registrations. |
| void didRegisterListener() { } |
| |
| /// This implementation ignores listener registrations. |
| void didUnregisterListener() { } |
| |
| /// Release the resources used by this object. The object is no longer usable |
| /// after this method is called. |
| @mustCallSuper |
| void dispose() { } |
| } |
| |
| /// A mixin that implements the [addListener]/[removeListener] protocol and notifies |
| /// all the registered listeners when [notifyListeners] is called. |
| /// |
| /// This mixin requires that the mixing class provide methods [didRegisterListener] |
| /// and [didUnregisterListener]. Implementations of these methods can be obtained |
| /// by mixing in another mixin from this library, such as [AnimationLazyListenerMixin]. |
| mixin AnimationLocalListenersMixin { |
| final ObserverList<VoidCallback> _listeners = ObserverList<VoidCallback>(); |
| |
| /// Called immediately before a listener is added via [addListener]. |
| /// |
| /// At the time this method is called the registered listener is not yet |
| /// notified by [notifyListeners]. |
| void didRegisterListener(); |
| |
| /// Called immediately after a listener is removed via [removeListener]. |
| /// |
| /// At the time this method is called the removed listener is no longer |
| /// notified by [notifyListeners]. |
| void didUnregisterListener(); |
| |
| /// Calls the listener every time the value of the animation changes. |
| /// |
| /// Listeners can be removed with [removeListener]. |
| void addListener(VoidCallback listener) { |
| didRegisterListener(); |
| _listeners.add(listener); |
| } |
| |
| /// Stop calling the listener every time the value of the animation changes. |
| /// |
| /// Listeners can be added with [addListener]. |
| void removeListener(VoidCallback listener) { |
| final bool removed = _listeners.remove(listener); |
| if (removed) { |
| didUnregisterListener(); |
| } |
| } |
| |
| /// Calls all the listeners. |
| /// |
| /// If listeners are added or removed during this function, the modifications |
| /// will not change which listeners are called during this iteration. |
| void notifyListeners() { |
| final List<VoidCallback> localListeners = List<VoidCallback>.from(_listeners); |
| for (final VoidCallback listener in localListeners) { |
| InformationCollector collector; |
| assert(() { |
| collector = () sync* { |
| yield DiagnosticsProperty<AnimationLocalListenersMixin>( |
| 'The $runtimeType notifying listeners was', |
| this, |
| style: DiagnosticsTreeStyle.errorProperty, |
| ); |
| }; |
| return true; |
| }()); |
| try { |
| if (_listeners.contains(listener)) |
| listener(); |
| } catch (exception, stack) { |
| FlutterError.reportError(FlutterErrorDetails( |
| exception: exception, |
| stack: stack, |
| library: 'animation library', |
| context: ErrorDescription('while notifying listeners for $runtimeType'), |
| informationCollector: collector, |
| )); |
| } |
| } |
| } |
| } |
| |
| /// A mixin that implements the addStatusListener/removeStatusListener protocol |
| /// and notifies all the registered listeners when notifyStatusListeners is |
| /// called. |
| /// |
| /// This mixin requires that the mixing class provide methods [didRegisterListener] |
| /// and [didUnregisterListener]. Implementations of these methods can be obtained |
| /// by mixing in another mixin from this library, such as [AnimationLazyListenerMixin]. |
| mixin AnimationLocalStatusListenersMixin { |
| final ObserverList<AnimationStatusListener> _statusListeners = ObserverList<AnimationStatusListener>(); |
| |
| /// Called immediately before a status listener is added via [addStatusListener]. |
| /// |
| /// At the time this method is called the registered listener is not yet |
| /// notified by [notifyStatusListeners]. |
| void didRegisterListener(); |
| |
| /// Called immediately after a status listener is removed via [removeStatusListener]. |
| /// |
| /// At the time this method is called the removed listener is no longer |
| /// notified by [notifyStatusListeners]. |
| void didUnregisterListener(); |
| |
| /// Calls listener every time the status of the animation changes. |
| /// |
| /// Listeners can be removed with [removeStatusListener]. |
| void addStatusListener(AnimationStatusListener listener) { |
| didRegisterListener(); |
| _statusListeners.add(listener); |
| } |
| |
| /// Stops calling the listener every time the status of the animation changes. |
| /// |
| /// Listeners can be added with [addStatusListener]. |
| void removeStatusListener(AnimationStatusListener listener) { |
| final bool removed = _statusListeners.remove(listener); |
| if (removed) { |
| didUnregisterListener(); |
| } |
| } |
| |
| /// Calls all the status listeners. |
| /// |
| /// If listeners are added or removed during this function, the modifications |
| /// will not change which listeners are called during this iteration. |
| void notifyStatusListeners(AnimationStatus status) { |
| final List<AnimationStatusListener> localListeners = List<AnimationStatusListener>.from(_statusListeners); |
| for (final AnimationStatusListener listener in localListeners) { |
| try { |
| if (_statusListeners.contains(listener)) |
| listener(status); |
| } catch (exception, stack) { |
| InformationCollector collector; |
| assert(() { |
| collector = () sync* { |
| yield DiagnosticsProperty<AnimationLocalStatusListenersMixin>( |
| 'The $runtimeType notifying status listeners was', |
| this, |
| style: DiagnosticsTreeStyle.errorProperty, |
| ); |
| }; |
| return true; |
| }()); |
| FlutterError.reportError(FlutterErrorDetails( |
| exception: exception, |
| stack: stack, |
| library: 'animation library', |
| context: ErrorDescription('while notifying status listeners for $runtimeType'), |
| informationCollector: collector |
| )); |
| } |
| } |
| } |
| } |