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// Copyright 2015 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 '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 (VoidCallback listener in localListeners) {
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: () sync* {
yield DiagnosticsProperty<AnimationLocalListenersMixin>(
'The $runtimeType notifying listeners was',
this,
style: DiagnosticsTreeStyle.errorProperty,
);
},
));
}
}
}
}
/// 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 (AnimationStatusListener listener in localListeners) {
try {
if (_statusListeners.contains(listener))
listener(status);
} catch (exception, stack) {
FlutterError.reportError(FlutterErrorDetails(
exception: exception,
stack: stack,
library: 'animation library',
context: ErrorDescription('while notifying status listeners for $runtimeType'),
informationCollector: () sync* {
yield DiagnosticsProperty<AnimationLocalStatusListenersMixin>(
'The $runtimeType notifying status listeners was',
this,
style: DiagnosticsTreeStyle.errorProperty,
);
},
));
}
}
}
}
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