Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit fe97a185 authored by Diego Vela's avatar Diego Vela
Browse files

Avoid Concurrent Exception in BaseDataProducer. 

Add locks to protect the list of consumers.
We are seeing concurrent modification exceptions because
DeviceStateManager sends changes on a separate thread.

Bug: 241464751
Test: n/a could not generate a non-flaky test.
Change-Id: Ie49c0f4f16db39187c98609ac57734e468c3f507
parent b53e6934

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

+34 −10
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 


package androidx.window.util;



import androidx.annotation.GuardedBy;

import androidx.annotation.NonNull;



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

 * {@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}.

 */

public abstract class BaseDataProducer<T> implements DataProducer<T> {



    private final Object mLock = new Object();

    @GuardedBy("mLock")

    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

    public final void addDataChangedCallback(@NonNull Consumer<T> callback) {

        synchronized (mLock) {

            mCallbacks.add(callback);

            Optional<T> 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<T> callback) {

        synchronized (mLock) {

            mCallbacks.remove(callback);

            onListenersChanged(mCallbacks);

        }

    }



    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

     * 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) {

        synchronized (mLock) {

            for (Consumer<T> callback : mCallbacks) {

                callback.accept(value);

            }

        }

    }

}
 
 No newline at end of file