Merge "Avoid Concurrent Exception in BaseDataProducer." into tm-qpr-dev am:... (b2bed0e6) · Commits · e / os / android_frameworks_base

libs/WindowManager/Jetpack/src/androidx/window/util/BaseDataProducer.java

+34 −10

Original line number	Original line	Diff line number	Diff line
	@@ -16,6 +16,7 @@

	package androidx.window.util;		package androidx.window.util;

			import androidx.annotation.GuardedBy;
	import androidx.annotation.NonNull;		import androidx.annotation.NonNull;

	import java.util.LinkedHashSet;		import java.util.LinkedHashSet;
	@@ -25,26 +26,46 @@ import java.util.function.Consumer;

	/**		/**
	* Base class that provides the implementation for the callback mechanism of the		* Base class that provides the implementation for the callback mechanism of the
	* {@link DataProducer} API.		* {@link DataProducer} API. This class is thread safe for adding, removing, and notifying
			* consumers.
	*		*
	* @param <T> The type of data this producer returns through {@link DataProducer#getData}.		* @param <T> The type of data this producer returns through {@link DataProducer#getData}.
	*/		*/
	public abstract class BaseDataProducer<T> implements DataProducer<T> {		public abstract class BaseDataProducer<T> implements DataProducer<T> {

			private final Object mLock = new Object();
			@GuardedBy("mLock")
	private final Set<Consumer<T>> mCallbacks = new LinkedHashSet<>();		private final Set<Consumer<T>> mCallbacks = new LinkedHashSet<>();

			/**
			* Adds a callback to the set of callbacks listening for data. Data is delivered through
			* {@link BaseDataProducer#notifyDataChanged(Object)}. This method is thread safe. Callers
			* should ensure that callbacks are thread safe.
			* @param callback that will receive data from the producer.
			*/
	@Override		@Override
	public final void addDataChangedCallback(@NonNull Consumer<T> callback) {		public final void addDataChangedCallback(@NonNull Consumer<T> callback) {
			synchronized (mLock) {
	mCallbacks.add(callback);		mCallbacks.add(callback);
	Optional<T> currentData = getCurrentData();		Optional<T> currentData = getCurrentData();
	currentData.ifPresent(callback);		currentData.ifPresent(callback);
	onListenersChanged(mCallbacks);		onListenersChanged(mCallbacks);
	}		}
			}

			/**
			* Removes a callback to the set of callbacks listening for data. This method is thread safe
			* for adding.
			* @param callback that was registered in
			* {@link BaseDataProducer#addDataChangedCallback(Consumer)}.
			*/
	@Override		@Override
	public final void removeDataChangedCallback(@NonNull Consumer<T> callback) {		public final void removeDataChangedCallback(@NonNull Consumer<T> callback) {
			synchronized (mLock) {
	mCallbacks.remove(callback);		mCallbacks.remove(callback);
	onListenersChanged(mCallbacks);		onListenersChanged(mCallbacks);
	}		}
			}

	protected void onListenersChanged(Set<Consumer<T>> callbacks) {}		protected void onListenersChanged(Set<Consumer<T>> callbacks) {}

	@@ -56,11 +77,14 @@ public abstract class BaseDataProducer<T> implements DataProducer<T> {

	/**		/**
	* Called to notify all registered consumers that the data provided		* Called to notify all registered consumers that the data provided
	* by {@link DataProducer#getData} has changed.		* by {@link DataProducer#getData} has changed. Calls to this are thread save but callbacks need
			* to ensure thread safety.
	*/		*/
	protected void notifyDataChanged(T value) {		protected void notifyDataChanged(T value) {
			synchronized (mLock) {
	for (Consumer<T> callback : mCallbacks) {		for (Consumer<T> callback : mCallbacks) {
	callback.accept(value);		callback.accept(value);
	}		}
	}		}
	}		}
			}
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