/*
* Copyright (c) 2013. wyouflf (wyouflf@gmail.com)
*
* 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.lidroid.xutils.task;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import com.lidroid.xutils.util.LogUtils;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Author: wyouflf
* Date: 14-5-23
* Time: 上午11:25
*/
public abstract class PriorityAsyncTask<Params, Progress, Result> implements TaskHandler {
private static final int MESSAGE_POST_RESULT = 0x1;
private static final int MESSAGE_POST_PROGRESS = 0x2;
private static final InternalHandler sHandler = new InternalHandler();
public static final Executor sDefaultExecutor = new PriorityExecutor();
private final WorkerRunnable<Params, Result> mWorker;
private final FutureTask<Result> mFuture;
private volatile boolean mExecuteInvoked = false;
private final AtomicBoolean mCancelled = new AtomicBoolean();
private final AtomicBoolean mTaskInvoked = new AtomicBoolean();
private Priority priority;
public Priority getPriority() {
return priority;
}
public void setPriority(Priority priority) {
this.priority = priority;
}
/**
* Creates a new asynchronous task. This constructor must be invoked on the UI thread.
*/
public PriorityAsyncTask() {
//这一块为什么不直接使用Runnable， 我的见解是这种使用能获取返回值
mWorker = new WorkerRunnable<Params, Result>() {
public Result call() throws Exception { //在子线程中运行
mTaskInvoked.set(true);
android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_BACKGROUND);
//noinspection unchecked
return postResult(doInBackground(mParams));
}
};
mFuture = new FutureTask<Result>(mWorker) { //
@Override
protected void done() {
try {
postResultIfNotInvoked(get());
} catch (InterruptedException e) {
LogUtils.d(e.getMessage());
} catch (ExecutionException e) {
throw new RuntimeException("An error occured while executing doInBackground()",
e.getCause());
} catch (CancellationException e) {
postResultIfNotInvoked(null);
}
}
};
}
private void postResultIfNotInvoked(Result result) {
final boolean wasTaskInvoked = mTaskInvoked.get();
if (!wasTaskInvoked) {
postResult(result);
}
}
private Result postResult(Result result) {
@SuppressWarnings("unchecked")
Message message = sHandler.obtainMessage(MESSAGE_POST_RESULT,
new AsyncTaskResult<Result>(this, result));
message.sendToTarget();
return result;
}
/**
* 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.
* <p/>
* 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 Result doInBackground(Params... params);
/**
* Runs on the UI thread before {@link #doInBackground}.
*
* @see #onPostExecute
* @see #doInBackground
*/
protected void onPreExecute() {
}
/**
* <p>Runs on the UI thread after {@link #doInBackground}. The
* specified result is the value returned by {@link #doInBackground}.</p>
* <p/>
* <p>This method won't be invoked if the task was cancelled.</p>
*
* @param result The result of the operation computed by {@link #doInBackground}.
* @see #onPreExecute
* @see #doInBackground
* @see #onCancelled(Object)
*/
@SuppressWarnings({"UnusedDeclaration"})
protected void onPostExecute(Result 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"}) //见HttpHandler中重写的这个方法
protected void onProgressUpdate(Progress... values) {
}
/**
* <p>Runs on the UI thread after {@link #cancel(boolean)} is invoked and
* {@link #doInBackground(Object[])} has finished.</p>
* <p/>
* <p>The default implementation simply invokes {@link #onCancelled()} and
* ignores the result. If you write your own implementation, do not call
* <code>super.onCancelled(result)</code>.</p>
*
* @param result The result, if any, computed in
* {@link #doInBackground(Object[])}, can be null
* @see #cancel(boolean)
* @see #isCancelled()
*/
@SuppressWarnings({"UnusedParameters"})
protected void onCancelled(Result result) {
onCancelled();
}
/**
* <p>Applications should preferably override {@link #onCancelled(Object)}.
* This method is invoked by the default implementation of
* {@link #onCancelled(Object)}.</p>
* <p/>
* <p>Runs on the UI thread after {@link #cancel(boolean)} is invoked and
* {@link #doInBackground(Object[])} has finished.</p>
*
* @see #onCancelled(Object)
* @see #cancel(boolean)
* @see #isCancelled()
*/
protected void onCancelled() {
}
/**
* Returns <tt>true</tt> if this task was cancelled before it completed
* normally. If you are calling {@link #cancel(boolean)} on the task,
* the value returned by this method should be checked periodically from
* {@link #doInBackground(Object[])} to end the task as soon as possible.
*
* @return <tt>true</tt> if task was cancelled before it completed
* @see #cancel(boolean)
*/
@Override
public final boolean isCancelled() {
return mCancelled.get();
}
/**
* @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(Object)
*/
public final boolean cancel(boolean mayInterruptIfRunning) {
mCancelled.set(true);
return mFuture.cancel(mayInterruptIfRunning);
}
@Override
public boolean supportPause() {
return false;
}
@Override
public boolean supportResume() {
return false;
}
@Override
public boolean supportCancel() {
return true;
}
@Override
public void pause() {
}
@Override
public void resume() {
}
@Override
public void cancel() {
this.cancel(true);
}
@Override
public boolean isPaused() {
return false;
}
/**
* Waits if necessary for the computation to complete, and then
* retrieves its result.
*
* @return The computed result.
* @throws java.util.concurrent.CancellationException If the computation was cancelled.
* @throws java.util.concurrent.ExecutionException If the computation threw an exception.
* @throws InterruptedException If the current thread was interrupted
* while waiting.
*/
public final Result 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 java.util.concurrent.CancellationException If the computation was cancelled.
* @throws java.util.concurrent.ExecutionException If the computation threw an exception.
* @throws InterruptedException If the current thread was interrupted
* while waiting.
* @throws java.util.concurrent.TimeoutException If the wait timed out.
*/
public final Result get(long timeout, TimeUnit unit) throws InterruptedException,
ExecutionException, TimeoutException {
return mFuture.get(timeout, unit);
}
/**
* @param params The parameters of the task.
* @return This instance of AsyncTask.
* @throws IllegalStateException If execute has invoked.
* @see #executeOnExecutor(java.util.concurrent.Executor, Object[])
* @see #execute(Runnable)
*/
public final PriorityAsyncTask<Params, Progress, Result> execute(Params... params) {
return executeOnExecutor(sDefaultExecutor, params);
}
/**
* @param exec The executor to use.
* @param params The parameters of the task.
* @return This instance of AsyncTask.
* @throws IllegalStateException If execute has invoked.
* @see #execute(Object[])
*/
public final PriorityAsyncTask<Params, Progress, Result> executeOnExecutor(Executor exec,
Params... params) {
if (mExecuteInvoked) {
throw new IllegalStateException("Cannot execute task:"
+ " the task is already executed.");
}
mExecuteInvoked = true;
onPreExecute();
mWorker.mParams = params;
exec.execute(new PriorityRunnable(priority, mFuture));
return this;
}
/**
* Convenience version of {@link #execute(Object...)} for use with
* a simple Runnable object. See {@link #execute(Object[])} for more
* information on the order of execution.
*
* @see #execute(Object[])
* @see #executeOnExecutor(java.util.concurrent.Executor, Object[])
*/
public static void execute(Runnable runnable) {
execute(runnable, Priority.DEFAULT);
}
/**
* Convenience version of {@link #execute(Object...)} for use with
* a simple Runnable object. See {@link #execute(Object[])} for more
* information on the order of execution.
*
* @see #execute(Object[])
* @see #executeOnExecutor(java.util.concurrent.Executor, Object[])
*/
public static void execute(Runnable runnable, Priority priority) {
sDefaultExecutor.execute(new PriorityRunnable(priority, runnable));
}
/**
* 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.
* <p/>
* {@link #onProgressUpdate} will note be called if the task has been
* canceled.
*
* @param values The progress values to update the UI with.
* @see #onProgressUpdate
* @see #doInBackground
*/
protected final void publishProgress(Progress... values) {
if (!isCancelled()) {
sHandler.obtainMessage(MESSAGE_POST_PROGRESS,
new AsyncTaskResult<Progress>(this, values)).sendToTarget();
}
}
private void finish(Result result) {
if (isCancelled()) {
onCancelled(result);
} else {
onPostExecute(result);
}
}
private static class InternalHandler extends Handler {
private InternalHandler() {
super(Looper.getMainLooper()); //这里很关键 这个是在UI线程中创建handler， 可以跟新界面。 （handler通信机制不了解的需要去具体了解）
}
@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]); // 任务完成后， 主要控制的是任务的生命周期
break;
case MESSAGE_POST_PROGRESS:
result.mTask.onProgressUpdate(result.mData); //主要是用于回调callback中的方法
break;
}
}
}
private static abstract class WorkerRunnable<Params, Result> implements Callable<Result> {
Params[] mParams;
}
@SuppressWarnings({"RawUseOfParameterizedType"})
private static class AsyncTaskResult<Data> {
final PriorityAsyncTask mTask;
final Data[] mData;
AsyncTaskResult(PriorityAsyncTask task, Data... data) {
mTask = task;
mData = data;
}
}
}