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/*
* Copyright (C) 2016 Google Inc.
*
* 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 com.google.android.mobly.snippet.util;
import android.os.Handler;
import android.os.Looper;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
public class MainThread {
/**
* Wraps a {@link Callable} in a {@link Runnable} that has a way to get the return value and
* exception after the fact.
*/
private static class CallableWrapper<T> implements Runnable {
private final Callable<T> mCallable;
private final CountDownLatch mLatch = new CountDownLatch(1);
private T mReturnValue;
private Throwable mException;
public CallableWrapper(Callable<T> callable) {
mCallable = callable;
}
@Override
public final void run() {
try {
mReturnValue = mCallable.call();
} catch (Throwable t) {
mException = t;
} finally {
mLatch.countDown();
}
}
public void awaitTermination() throws InterruptedException {
mLatch.await();
}
public T getReturnValue() {
return mReturnValue;
}
public Throwable getException() {
return mException;
}
}
private static final Handler sMainThreadHandler = new Handler(Looper.getMainLooper());
private MainThread() {
// Utility class.
}
/** Executed in the main thread. Returns the result of an execution or any exception thrown. */
public static <T> T run(final Callable<T> task) throws Exception {
CallableWrapper<T> wrapper = new CallableWrapper<>(task);
return runCallableWrapper(wrapper);
}
private static <T> T runCallableWrapper(CallableWrapper<T> wrapper) throws Exception {
sMainThreadHandler.post(wrapper);
wrapper.awaitTermination();
Throwable exception = wrapper.getException();
if (exception != null) {
if (exception instanceof RuntimeException) {
throw (RuntimeException) exception;
}
if (exception instanceof Error) {
throw (Error) exception;
}
throw (Exception) exception;
}
return wrapper.getReturnValue();
}
}
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