在列表视图适配器完成之前取消asynctask

Question

我需要取消我的asynctask填充列表视图适配器之前，它已经完成按后退按钮。通过这个代码

@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();
                }

这是一个适配器类，我们无法通过按后退键来取消它。按下后退键，活动被关闭，但后台任务仍在继续。

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

我已经试过了，但是没有用…!!

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();

详细代码:

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();
                }