在完成之前取消列表视图适配器的异步任务

Question

我需要在完成之前通过按返回按钮取消填充列表视图适配器的异步任务。通过这段代码

@Override
public View getView(final int position, View convertView, ViewGroup parent) {

    if(convertView==null){
        LayoutInflater inflater=(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);convertView=inflater.inflate(R.layout.seatadapter, null);

         TextView text3=(TextView)convertView.findViewById(R.id.text3);
         ProgressBar progressBar1=(ProgressBar)convertView.findViewById(R.id.progressBar1);
         TextView predic=(TextView)convertView.findViewById(R.id.textView3);
         TextView classs=(TextView)convertView.findViewById(R.id.textView4);
         ImageView img1=(ImageView)convertView.findViewById(R.id.imageView1);

new update(classs,predic, text3, progressBar1,img1).execute(tarinname.get(position), Date.get(position), Ffrom.get(position), Tto.get(position), Ccl.get(position));

class update extends AsyncTask{

@Override
        protected Object doInBackground(Object... params) {

Code For Json Parsing....
}
        protected void onPostExecute(Object result) {
            super.onPostExecute(result);

            if (this.result.contains("CurrentStatus")) {
                 progressBar.setVisibility(progressBar.GONE);

                 t.setVisibility(t.VISIBLE);
                 t3.setVisibility(t3.VISIBLE);
                im1.setVisibility(im1.VISIBLE);

                 t3.setText("Class "+TravelClass);

                 t1.setText(perdcition);

                 if (ConfirmTktStatus.contains("Confirm")) {
                    im1.setImageResource(R.drawable.img_green);

                }
                 if (ConfirmTktStatus.contains("Probable")) {

                    }
                 if (ConfirmTktStatus.contains("No Chance")) {

                    }

                t.setText(var1);

            }else {
                 progressBar.setVisibility(progressBar.GONE);
            }


                Toast.makeText(context, var, Toast.LENGTH_LONG).show();
                }

这是适配器类，我们无法在其过程中通过按返回按钮来取消它。按下后退按钮时，活动关闭，但后台任务继续。

@Override
            protected void onCancelled() {
                // TODO Auto-generated method stub
                super.onCancelled();
                ((Activity)context).finish();

            }

我已经试过了，但没用..!!

Answer 1

请创建一个列表来存储当前的 AsyncTask，然后随时取消它

for (AsyncTask myAsyncTask : myAsyncTasks) {
    if (myAsyncTask.getStatus().equals(AsyncTask.Status.RUNNING)) {
        myAsyncTask.cancel(true);
    }
}
myAsyncTasks.clear();

您的代码的详细信息：

private List<AsyncTask> myAsyncTasks = new ArrayList<>();
public void addRunningTask(AsyncTask task) {
    myAsyncTasks.add(task);
}

public void cancelRunningTasks() {
    for (AsyncTask myAsyncTask : myAsyncTasks) {
        if (myAsyncTask.getStatus().equals(AsyncTask.Status.RUNNING)) {
            myAsyncTask.cancel(true);
        }
    }
    myAsyncTasks.clear();
}
@Override
public void onBackPressed() {
    cancelRunningTasks();
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {

    if(convertView==null){
        LayoutInflater inflater=(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);convertView=inflater.inflate(R.layout.seatadapter, null);

         TextView text3=(TextView)convertView.findViewById(R.id.text3);
         ProgressBar progressBar1=(ProgressBar)convertView.findViewById(R.id.progressBar1);
         TextView predic=(TextView)convertView.findViewById(R.id.textView3);
         TextView classs=(TextView)convertView.findViewById(R.id.textView4);
         ImageView img1=(ImageView)convertView.findViewById(R.id.imageView1);

AsyncTask task = new update(classs,predic, text3, progressBar1,img1);
task.execute(tarinname.get(position), Date.get(position), Ffrom.get(position), Tto.get(position), Ccl.get(position));
addRunningTask(task);

class update extends AsyncTask{

@Override
        protected Object doInBackground(Object... params) {

Code For Json Parsing....
}
        protected void onPostExecute(Object result) {
            super.onPostExecute(result);

            if (this.result.contains("CurrentStatus")) {
                 progressBar.setVisibility(progressBar.GONE);

                 t.setVisibility(t.VISIBLE);
                 t3.setVisibility(t3.VISIBLE);
                im1.setVisibility(im1.VISIBLE);

                 t3.setText("Class "+TravelClass);

                 t1.setText(perdcition);

                 if (ConfirmTktStatus.contains("Confirm")) {
                    im1.setImageResource(R.drawable.img_green);

                }
                 if (ConfirmTktStatus.contains("Probable")) {

                    }
                 if (ConfirmTktStatus.contains("No Chance")) {

                    }

                t.setText(var1);

            }else {
                 progressBar.setVisibility(progressBar.GONE);
            }


                Toast.makeText(context, var, Toast.LENGTH_LONG).show();
                }