AsyncTask< 地址类型Params, 进度值类型Progress， 结果类型Result> {    //String、URL, Integer, Bitmap、void

        onPreExecute(){    //运行在主线程MainThread，准备工作 }

                totalLen = connection.getContentLength();

        protect Result doInBackground(Params... params) {        //运行在子线程WorkThread，耗时操作        return result；}

                int progress = (int) (curLen*100/(double)totalLen);

                publishProgress(progress);

        onPostExcute(Result result) {        //在主线程中调用,处理结果  }

                BitmapFactory.decodeByteArray(bytes, 0, bytes.length);        把一个字节数组变成Bitmap对象

        onProgressUpdate(Progress... progress) {        //在publishProgress()调用之后在主线程调用，用来显示进度值 }

                ProgressDialog dialog = new ProgressDialog(this);

                dialog.setTitle("...");

                dialog.setProgressStyled(ProgressDialog.STYLE_HORIZONTAL);

                dialog.setIcon(...);

                dialog.setMessage("Loading...");

                dialog.setCanceledOnTouchOutside(false);

                dialog.show();

                dialog.setProgress(int value);

                dialog.setOnDismissListener(

                      onDismiss(DialogInterface dialog) {       //myAsync.cancel(true);    }

                )

                dialog.dismiss();

        onCanceled(Result result) {        //取消异步任务之后再主线程中运行}

}

主线程：new MyAsyncTask.excute(path);//一个MyAsyncTask对象只能调用excute()一次