Android Open Source - android-smart-imageview Image Async Task

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License

The source code is released under:

MIT License

Java Source Code

package me.caiying.asiv;
//from w w w.  j  a  v  a  2  s. c o  m
import java.lang.reflect.Method;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;

import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;


public abstract class ImageAsyncTask<Void, Integer, Bitmap> {
    private static final String LOG_TAG = "IgAsyncTask";

    private static final int CORE_POOL_SIZE = 5;
    private static final int MAXIMUM_POOL_SIZE = 128;
    private static final int KEEP_ALIVE = 10;

    private static final BlockingQueue<Runnable> sWorkQueue = new LinkedBlockingQueue<Runnable>(10);

    private static final ThreadFactory sThreadFactory = new ThreadFactory() {
        private final AtomicInteger mCount = new AtomicInteger(1);

        public Thread newThread(Runnable r) {
            return new Thread(r, "IgAsyncTask #" + mCount.getAndIncrement());
        }
    };

    private static final ThreadPoolExecutor sExecutor = new ThreadPoolExecutor(CORE_POOL_SIZE,
            MAXIMUM_POOL_SIZE, KEEP_ALIVE, TimeUnit.SECONDS, sWorkQueue, sThreadFactory);

    private static final int MESSAGE_POST_RESULT = 0x1;
    private static final int MESSAGE_POST_PROGRESS = 0x2;
    private static final int MESSAGE_POST_CANCEL = 0x3;

    private static final InternalHandler sHandler = new InternalHandler();

    private final WorkerRunnable<Void, Bitmap> mWorker;
    private final FutureTask<Bitmap> mFuture;

    private volatile Status mStatus = Status.PENDING;

    /**
     * Indicates the current status of the task. Each status will be set only once
     * during the lifetime of a task.
     */
    public enum Status {
        /**
         * Indicates that the task has not been executed yet.
         */
        PENDING,
        /**
         * Indicates that the task is running.
         */
        RUNNING,
        /**
         * Indicates that {@link AsyncTask#onPostExecute} has finished.
         */
        FINISHED,
    }

    /**
     * Creates a new asynchronous task. This constructor must be invoked on the UI thread.
     */
    public ImageAsyncTask() {
        mWorker = new WorkerRunnable<Void, Bitmap>() {
            public Bitmap call() throws Exception {
//                java.lang.Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
                Class clazz = Class.forName("java.lang.Process");
                Method method= clazz.getMethod("setThreadPriority", int.class);
                method.invoke(clazz, clazz.getField("THREAD_PRIORITY_BACKGROUND"));
                return doInBackground(mParams);
            }
        };

        mFuture = new FutureTask<Bitmap>(mWorker) {
            @Override
            protected void done() {
                Message message;
                Bitmap result = null;

                try {
                    result = get();
                } catch (InterruptedException e) {
                    android.util.Log.w(LOG_TAG, e);
                } catch (ExecutionException e) {
                    throw new RuntimeException("An error occured while executing doInBackground()",
                            e.getCause());
                } catch (CancellationException e) {
                    message = sHandler.obtainMessage(MESSAGE_POST_CANCEL,
                            new AsyncTaskResult<Bitmap>(ImageAsyncTask.this, (Bitmap[]) null));
                    message.sendToTarget();
                    return;
                } catch (Throwable t) {
                    throw new RuntimeException("An error occured while executing "
                            + "doInBackground()", t);
                }

                message = sHandler.obtainMessage(MESSAGE_POST_RESULT,
                        new AsyncTaskResult<Bitmap>(ImageAsyncTask.this, result));
                message.sendToTarget();
            }
        };
    }

    /**
     * Returns the current status of this task.
     *
     * @return The current status.
     */
    public final Status getStatus() {
        return mStatus;
    }

    /**
     * Override this method to perform a computation on a background thread. The
     * specified parameters are the parameters passed to {@link #execute}
     * by the caller of this task.
     *
     * This method can call {@link #publishProgress} to publish updates
     * on the UI thread.
     *
     * @param params The parameters of the task.
     *
     * @return A result, defined by the subclass of this task.
     *
     * @see #onPreExecute()
     * @see #onPostExecute
     * @see #publishProgress
     */
    protected abstract Bitmap doInBackground(Void... params);

    /**
     * Runs on the UI thread before {@link #doInBackground}.
     *
     * @see #onPostExecute
     * @see #doInBackground
     */
    protected void onPreExecute() {
    }

    /**
     * Runs on the UI thread after {@link #doInBackground}. The
     * specified result is the value returned by {@link #doInBackground}
     * or null if the task was cancelled or an exception occured.
     *
     * @param result The result of the operation computed by {@link #doInBackground}.
     *
     * @see #onPreExecute
     * @see #doInBackground
     */
    @SuppressWarnings({"UnusedDeclaration"})
    protected void onPostExecute(Bitmap result) {
    }

    /**
     * Runs on the UI thread after {@link #publishProgress} is invoked.
     * The specified values are the values passed to {@link #publishProgress}.
     *
     * @param values The values indicating progress.
     *
     * @see #publishProgress
     * @see #doInBackground
     */
    @SuppressWarnings({"UnusedDeclaration"})
    protected void onProgressUpdate(Integer... values) {
    }

    /**
     * Runs on the UI thread after {@link #cancel(boolean)} is invoked.
     *
     * @see #cancel(boolean)
     * @see #isCancelled()
     */
    protected void onCancelled() {
    }

    /**
     * Returns <tt>true</tt> if this task was cancelled before it completed
     * normally.
     *
     * @return <tt>true</tt> if task was cancelled before it completed
     *
     * @see #cancel(boolean)
     */
    public final boolean isCancelled() {
        return mFuture.isCancelled();
    }

    /**
     * Attempts to cancel execution of this task.  This attempt will
     * fail if the task has already completed, already been cancelled,
     * or could not be cancelled for some other reason. If successful,
     * and this task has not started when <tt>cancel</tt> is called,
     * this task should never run.  If the task has already started,
     * then the <tt>mayInterruptIfRunning</tt> parameter determines
     * whether the thread executing this task should be interrupted in
     * an attempt to stop the task.
     *
     * @param mayInterruptIfRunning <tt>true</tt> if the thread executing this
     *        task should be interrupted; otherwise, in-progress tasks are allowed
     *        to complete.
     *
     * @return <tt>false</tt> if the task could not be cancelled,
     *         typically because it has already completed normally;
     *         <tt>true</tt> otherwise
     *
     * @see #isCancelled()
     * @see #onCancelled()
     */
    public final boolean cancel(boolean mayInterruptIfRunning) {
        return mFuture.cancel(mayInterruptIfRunning);
    }

    /**
     * Waits if necessary for the computation to complete, and then
     * retrieves its result.
     *
     * @return The computed result.
     *
     * @throws CancellationException If the computation was cancelled.
     * @throws ExecutionException If the computation threw an exception.
     * @throws InterruptedException If the current thread was interrupted
     *         while waiting.
     */
    public final Bitmap get() throws InterruptedException, ExecutionException {
        return mFuture.get();
    }

    /**
     * Waits if necessary for at most the given time for the computation
     * to complete, and then retrieves its result.
     *
     * @param timeout Time to wait before cancelling the operation.
     * @param unit The time unit for the timeout.
     *
     * @return The computed result.
     *
     * @throws CancellationException If the computation was cancelled.
     * @throws ExecutionException If the computation threw an exception.
     * @throws InterruptedException If the current thread was interrupted
     *         while waiting.
     * @throws TimeoutException If the wait timed out.
     */
    public final Bitmap get(long timeout, TimeUnit unit) throws InterruptedException,
            ExecutionException, TimeoutException {
        return mFuture.get(timeout, unit);
    }

    /**
     * Executes the task with the specified parameters. The task returns
     * itself (this) so that the caller can keep a reference to it.
     *
     * This method must be invoked on the UI thread.
     *
     * @param params The parameters of the task.
     *
     * @return This instance of AsyncTask.
     *
     * @throws IllegalStateException If {@link #getStatus()} returns either
     *         {@link AsyncTask.Status#RUNNING} or {@link AsyncTask.Status#FINISHED}.
     */
    public final ImageAsyncTask<Void, Integer, Bitmap> execute(Void... params) {
        if (mStatus != Status.PENDING) {
            switch (mStatus) {
                case RUNNING:
                    throw new IllegalStateException("Cannot execute task:"
                            + " the task is already running.");
                case FINISHED:
                    throw new IllegalStateException("Cannot execute task:"
                            + " the task has already been executed "
                            + "(a task can be executed only once)");
            }
        }

        mStatus = Status.RUNNING;

        onPreExecute();

        mWorker.mParams = params;
        sExecutor.execute(mFuture);

        return this;
    }

    /**
     * This method can be invoked from {@link #doInBackground} to
     * publish updates on the UI thread while the background computation is
     * still running. Each call to this method will trigger the execution of
     * {@link #onProgressUpdate} on the UI thread.
     *
     * @param values The progress values to update the UI with.
     *
     * @see #onProgressUpdate
     * @see #doInBackground
     */
    protected final void publishProgress(Integer... values) {
        sHandler.obtainMessage(MESSAGE_POST_PROGRESS,
                new AsyncTaskResult<Integer>(this, values)).sendToTarget();
    }

    private void finish(Bitmap result) {
        if (isCancelled()) result = null;
        onPostExecute(result);
        mStatus = Status.FINISHED;
    }

    private static class InternalHandler extends Handler {
        @SuppressWarnings({"unchecked", "RawUseOfParameterizedType"})
        @Override
        public void handleMessage(Message msg) {
            AsyncTaskResult result = (AsyncTaskResult) msg.obj;
            switch (msg.what) {
                case MESSAGE_POST_RESULT:
                    // There is only one result
                    result.mTask.finish(result.mData[0]);
                    break;
                case MESSAGE_POST_PROGRESS:
                    result.mTask.onProgressUpdate(result.mData);
                    break;
                case MESSAGE_POST_CANCEL:
                    result.mTask.onCancelled();
                    break;
            }
        }
    }

    private static abstract class WorkerRunnable<Params, Result> implements Callable<Result> {
        Params[] mParams;
    }

    @SuppressWarnings({"RawUseOfParameterizedType"})
    private static class AsyncTaskResult<Data> {
        final ImageAsyncTask mTask;
        final Data[] mData;

        AsyncTaskResult(ImageAsyncTask task, Data... data) {
            mTask = task;
            mData = data;
        }
    }
}

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