HandlerAdapterExecutor.java
/*
* Copyright 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.camera.core.impl.utils.executor;
import android.os.Handler;
import android.os.Looper;
import androidx.annotation.NonNull;
import androidx.core.util.Preconditions;
import java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;
/**
* An implementation of {@link Executor} which delegates all tasks to the given {@link Handler}.
*/
final class HandlerAdapterExecutor implements Executor {
private static ThreadLocal<Executor> sHandlerThreadLocal =
new ThreadLocal<Executor>() {
@Override
public Executor initialValue() {
if (Looper.myLooper() == Looper.getMainLooper()) {
return CameraXExecutors.mainThreadExecutor();
} else if (Looper.myLooper() != null) {
Handler handler = new Handler(Looper.myLooper());
return new HandlerAdapterExecutor(handler);
}
return null;
}
};
private final Handler mHandler;
HandlerAdapterExecutor(@NonNull Handler handler) {
mHandler = Preconditions.checkNotNull(handler);
}
/**
* Retrieves a cached executor derived from the current thread's looper.
*/
static Executor currentThreadExecutor() {
Executor executor = sHandlerThreadLocal.get();
if (executor == null) {
Looper looper = Looper.myLooper();
if (looper == null) {
throw new IllegalStateException("Current thread has no looper!");
}
executor = new HandlerAdapterExecutor(new Handler(looper));
sHandlerThreadLocal.set(executor);
}
return executor;
}
@Override
public void execute(Runnable command) {
if (!mHandler.post(command)) {
throw new RejectedExecutionException(mHandler + " is shutting down");
}
}
}