diff --git a/libs/WindowManager/Jetpack/src/androidx/window/util/BaseDataProducer.java b/libs/WindowManager/Jetpack/src/androidx/window/util/BaseDataProducer.java index 0da44ac36a6e4..cbaa277120154 100644 --- a/libs/WindowManager/Jetpack/src/androidx/window/util/BaseDataProducer.java +++ b/libs/WindowManager/Jetpack/src/androidx/window/util/BaseDataProducer.java @@ -16,6 +16,7 @@ package androidx.window.util; +import androidx.annotation.GuardedBy; import androidx.annotation.NonNull; import java.util.LinkedHashSet; @@ -25,25 +26,45 @@ import java.util.function.Consumer; /** * 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 The type of data this producer returns through {@link DataProducer#getData}. */ public abstract class BaseDataProducer implements DataProducer { + + private final Object mLock = new Object(); + @GuardedBy("mLock") private final Set> 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 public final void addDataChangedCallback(@NonNull Consumer callback) { - mCallbacks.add(callback); - Optional currentData = getCurrentData(); - currentData.ifPresent(callback); - onListenersChanged(mCallbacks); + synchronized (mLock) { + mCallbacks.add(callback); + Optional currentData = getCurrentData(); + currentData.ifPresent(callback); + 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 public final void removeDataChangedCallback(@NonNull Consumer callback) { - mCallbacks.remove(callback); - onListenersChanged(mCallbacks); + synchronized (mLock) { + mCallbacks.remove(callback); + onListenersChanged(mCallbacks); + } } protected void onListenersChanged(Set> callbacks) {} @@ -56,11 +77,14 @@ public abstract class BaseDataProducer implements DataProducer { /** * 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) { - for (Consumer callback : mCallbacks) { - callback.accept(value); + synchronized (mLock) { + for (Consumer callback : mCallbacks) { + callback.accept(value); + } } } } \ No newline at end of file