MainThreadExecutor.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 java.util.concurrent.Executor;
import java.util.concurrent.RejectedExecutionException;
/**
* An Executor which will post to the main thread.
*/
final class MainThreadExecutor implements Executor {
private static volatile Executor sExecutor;
private final Handler mMainThreadHandler;
private MainThreadExecutor() {
mMainThreadHandler = new Handler(Looper.getMainLooper());
}
static Executor getInstance() {
if (sExecutor != null) {
return sExecutor;
}
synchronized (MainThreadExecutor.class) {
if (sExecutor == null) {
sExecutor = new MainThreadExecutor();
}
}
return sExecutor;
}
@Override
public void execute(@NonNull Runnable command) {
if (!mMainThreadHandler.post(command)) {
throw new RejectedExecutionException(mMainThreadHandler + " is shutting down");
}
}
}