android.support.test.espresso.base.ThreadPoolExecutorExtractor.java Source code

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Here is the source code for android.support.test.espresso.base.ThreadPoolExecutorExtractor.java

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/*
 * Copyright (C) 2014 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 android.support.test.espresso.base;

import com.google.common.base.Optional;

import android.os.Build;
import android.os.Handler;
import android.os.Looper;

import java.lang.reflect.Field;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
import java.util.concurrent.ThreadPoolExecutor;

import javax.inject.Inject;
import javax.inject.Singleton;

/**
 * Extracts ThreadPoolExecutors used by pieces of android.
 *
 * We do some work to ensure that we load the classes containing these thread pools
 * on the main thread, since they may have static initialization that assumes access
 * to the main looper.
 */
@Singleton
final class ThreadPoolExecutorExtractor {
    private static final String ASYNC_TASK_CLASS_NAME = "android.os.AsyncTask";
    private static final String MODERN_ASYNC_TASK_CLASS_NAME = "android.support.v4.content.ModernAsyncTask";
    private static final String MODERN_ASYNC_TASK_FIELD_NAME = "THREAD_POOL_EXECUTOR";
    private static final String LEGACY_ASYNC_TASK_FIELD_NAME = "sExecutor";
    private final Handler mainHandler;

    @Inject
    ThreadPoolExecutorExtractor(Looper looper) {
        mainHandler = new Handler(looper);
    }

    public ThreadPoolExecutor getAsyncTaskThreadPool() {
        FutureTask<Optional<ThreadPoolExecutor>> getTask = null;
        if (Build.VERSION.SDK_INT < 11) {
            getTask = new FutureTask<Optional<ThreadPoolExecutor>>(LEGACY_ASYNC_TASK_EXECUTOR);
        } else {
            getTask = new FutureTask<Optional<ThreadPoolExecutor>>(POST_HONEYCOMB_ASYNC_TASK_EXECUTOR);
        }

        try {
            return runOnMainThread(getTask).get().get();
        } catch (InterruptedException ie) {
            throw new RuntimeException("Interrupted while trying to get the async task executor!", ie);
        } catch (ExecutionException ee) {
            throw new RuntimeException(ee.getCause());
        }
    }

    public Optional<ThreadPoolExecutor> getCompatAsyncTaskThreadPool() {
        try {
            return runOnMainThread(new FutureTask<Optional<ThreadPoolExecutor>>(MODERN_ASYNC_TASK_EXTRACTOR)).get();
        } catch (InterruptedException ie) {
            throw new RuntimeException("Interrupted while trying to get the compat async executor!", ie);
        } catch (ExecutionException ee) {
            throw new RuntimeException(ee.getCause());
        }
    }

    private <T> FutureTask<T> runOnMainThread(final FutureTask<T> futureToRun) {
        if (Looper.myLooper() != Looper.getMainLooper()) {
            final CountDownLatch latch = new CountDownLatch(1);
            mainHandler.post(new Runnable() {
                @Override
                public void run() {
                    try {
                        futureToRun.run();
                    } finally {
                        latch.countDown();
                    }
                }
            });
            try {
                latch.await();
            } catch (InterruptedException ie) {
                if (!futureToRun.isDone()) {
                    throw new RuntimeException("Interrupted while waiting for task to complete.");
                }
            }
        } else {
            futureToRun.run();
        }

        return futureToRun;
    }

    private static final Callable<Optional<ThreadPoolExecutor>> MODERN_ASYNC_TASK_EXTRACTOR = new Callable<Optional<ThreadPoolExecutor>>() {
        @Override
        public Optional<ThreadPoolExecutor> call() throws Exception {
            try {
                Class<?> modernClazz = Class.forName(MODERN_ASYNC_TASK_CLASS_NAME);
                Field executorField = modernClazz.getField(MODERN_ASYNC_TASK_FIELD_NAME);
                return Optional.of((ThreadPoolExecutor) executorField.get(null));
            } catch (ClassNotFoundException cnfe) {
                return Optional.<ThreadPoolExecutor>absent();
            } catch (NoSuchFieldException nsfe) {
                return Optional.<ThreadPoolExecutor>absent();
            }
        }
    };

    private static final Callable<Class<?>> LOAD_ASYNC_TASK_CLASS = new Callable<Class<?>>() {
        @Override
        public Class<?> call() throws Exception {
            return Class.forName(ASYNC_TASK_CLASS_NAME);
        }
    };

    private static final Callable<Optional<ThreadPoolExecutor>> LEGACY_ASYNC_TASK_EXECUTOR = new Callable<Optional<ThreadPoolExecutor>>() {
        @Override
        public Optional<ThreadPoolExecutor> call() throws Exception {
            try {
                Field executorField = LOAD_ASYNC_TASK_CLASS.call().getDeclaredField(LEGACY_ASYNC_TASK_FIELD_NAME);
                executorField.setAccessible(true);
                return Optional.of((ThreadPoolExecutor) executorField.get(null));
            } catch (ClassNotFoundException cnfe) {
                return Optional.<ThreadPoolExecutor>absent();
            } catch (NoSuchFieldException nsfe) {
                return Optional.<ThreadPoolExecutor>absent();
            }
        }
    };

    private static final Callable<Optional<ThreadPoolExecutor>> POST_HONEYCOMB_ASYNC_TASK_EXECUTOR = new Callable<Optional<ThreadPoolExecutor>>() {
        @Override
        public Optional<ThreadPoolExecutor> call() throws Exception {
            try {
                Field executorField = LOAD_ASYNC_TASK_CLASS.call().getField(MODERN_ASYNC_TASK_FIELD_NAME);
                return Optional.of((ThreadPoolExecutor) executorField.get(null));
            } catch (ClassNotFoundException cnfe) {
                return Optional.<ThreadPoolExecutor>absent();
            } catch (NoSuchFieldException nsfe) {
                return Optional.<ThreadPoolExecutor>absent();
            }
        }
    };
}