Android项目-高考作文-AsyncTask的不足

1, AsyncTask的不足. 

从android4.0开始, 后台只允许一个AsyncTask执行, 如果当前的AsyncTask没有执行完毕, 那么当前的请求一直处于等待状态. 直到上一个执行完毕. 并且还不能停止上一个AsyncTask. 但是为了快速响应应用的请求, 我们需要多个任务并行执行.

2, 基于AsyncTask的源码 改写自己的AsyncTask.

public abstract class AsyncTaskCustomize<Params, Result> {private static final int MESSAGE_POST_RESULT = 0;private Thread thread;private InternalHandler mHandler = new InternalHandler();private final AtomicBoolean mCancelled = new AtomicBoolean();private volatile Status mStatus = Status.PENDING;private WorkerRunnable<Params, Result> work;protected int key;public AsyncTaskCustomize(int key) {this.key = key;work = new WorkerRunnable<Params, Result>() {@Overridepublic void run() {Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);postResult(doInBackground(mParams));}};thread = new Thread(work);}public final boolean isCancelled() {return mCancelled.get();}private void postResult(Result result) {@SuppressWarnings("unchecked")Message message = mHandler.obtainMessage(MESSAGE_POST_RESULT,new AsyncTaskResult<Result>(this, result));message.sendToTarget();// return result;}public final AsyncTaskCustomize<Params, Result> execute(Params... params) {return executeTask(params);}/** * @param params */private AsyncTaskCustomize<Params, Result> executeTask(Params... 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)");default:break;}}onPreExecute();work.mParams = params;mStatus = Status.RUNNING;thread.start();return this;}/** * must add super.onPreExecute(result); */public void onPreExecute() {TaskController.getInstance().add(key, this);}/** * must add super.onPostExecute(result); */public void onPostExecute(Result result) {TaskController.getInstance().remove(key);}public abstract Result doInBackground(Params... params);private static final class InternalHandler extends Handler {@SuppressWarnings("unchecked")@Overridepublic void handleMessage(Message msg) {@SuppressWarnings("rawtypes")AsyncTaskResult result = (AsyncTaskResult) msg.obj;switch (msg.what) {case MESSAGE_POST_RESULT:// There is only one resultresult.mTask.finish(result.mData[0]);break;}}}private void finish(Result result) {if (isCancelled()) {onCancelled(result);} else {onPostExecute(result);}mStatus = Status.FINISHED;}public final boolean cancel() {if (isCancelled()) {return false;}if (mStatus == Status.FINISHED) {return false;}try {thread.interrupt();mCancelled.set(true);} catch (Exception e) {e.printStackTrace();return false;}return true;}/** * @param result */protected void onCancelled(Result result) {}protected void onCancelled() {}private static abstract class WorkerRunnable<Params, Result> implementsRunnable {Params[] mParams;}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,}@SuppressWarnings("rawtypes")private static class AsyncTaskResult<Data> {final AsyncTaskCustomize mTask;final Data[] mData;AsyncTaskResult(AsyncTaskCustomize task, Data... data) {mTask = task;mData = data;}}}