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Commit 762a2739 authored by Kenneth Ford's avatar Kenneth Ford
Browse files

Fix ConcurrentModificationException in AcceptOnceConsumer 

Marks AcceptOnceConsumer as ready to be removed instead
of removing from the set of callbacks while iterating

Bug: 260526969
Test: Manual, scenario where an AcceptOnceConsumer
  is created will trigger the crash provided more
  than one consumer exists
Change-Id: Ie85fd58b7d2abf0e865bca7737101ad42577e2ca
parent df9d2dc2

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

+18 −3
Original line number Diff line number Diff line
@@ -27,9 +27,10 @@ import java.util.function.Consumer; 
 */

public class AcceptOnceConsumer<T> implements Consumer<T> {

    private final Consumer<T> mCallback;

    private final DataProducer<T> mProducer;

    private final AcceptOnceProducerCallback<T> mProducer;



    public AcceptOnceConsumer(@NonNull DataProducer<T> producer, @NonNull Consumer<T> callback) {

    public AcceptOnceConsumer(@NonNull AcceptOnceProducerCallback<T> producer,

            @NonNull Consumer<T> callback) {

        mProducer = producer;

        mCallback = callback;

    }
@@ -37,6 +38,20 @@ public class AcceptOnceConsumer<T> implements Consumer<T> { 
    @Override

    public void accept(@NonNull T t) {

        mCallback.accept(t);

        mProducer.removeDataChangedCallback(this);

        mProducer.onConsumerReadyToBeRemoved(this);

    }



    /**

     * Interface to allow the {@link AcceptOnceConsumer} to notify the client that created it,

     * when it is ready to be removed. This allows the client to remove the consumer object

     * when it deems it is safe to do so.

     * @param <T> The type of data this callback accepts through {@link #onConsumerReadyToBeRemoved}

     */

    public interface AcceptOnceProducerCallback<T> {



        /**

         * Notifies that the given {@code callback} is ready to be removed

         */

        void onConsumerReadyToBeRemoved(Consumer<T> callback);

    }

}

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

+25 −1
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ package androidx.window.util; 
import androidx.annotation.GuardedBy;

import androidx.annotation.NonNull;



import java.util.HashSet;

import java.util.LinkedHashSet;

import java.util.Optional;

import java.util.Set;
@@ -31,11 +32,14 @@ import java.util.function.Consumer; 
 *

 * @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>,

        AcceptOnceConsumer.AcceptOnceProducerCallback<T> {



    private final Object mLock = new Object();

    @GuardedBy("mLock")

    private final Set<Consumer<T>> mCallbacks = new LinkedHashSet<>();

    @GuardedBy("mLock")

    private final Set<Consumer<T>> mCallbacksToRemove = new HashSet<>();



    /**

     * Adds a callback to the set of callbacks listening for data. Data is delivered through
@@ -85,6 +89,26 @@ public abstract class BaseDataProducer<T> implements DataProducer<T> { 
            for (Consumer<T> callback : mCallbacks) {

                callback.accept(value);

            }

            removeFinishedCallbacksLocked();

        }

    }



    /**

     * Removes any callbacks that notified us through {@link #onConsumerReadyToBeRemoved(Consumer)}

     * that they are ready to be removed.

     */

    @GuardedBy("mLock")

    private void removeFinishedCallbacksLocked() {

        for (Consumer<T> callback: mCallbacksToRemove) {

            mCallbacks.remove(callback);

        }

        mCallbacksToRemove.clear();

    }



    @Override

    public void onConsumerReadyToBeRemoved(Consumer<T> callback) {

        synchronized (mLock) {

            mCallbacksToRemove.add(callback);

        }

    }

}
 
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