how to stop a running async task?

Question

I am running a async task in android to ping t a particular URL but the problem is when the url is not valid or not reachable an exception occurs as sockettimeoutexception so on that exception i want to stop the running task. iagve tried using Cancel() method but that causes App crash.

I am using the following code.

private class UrlDataProvider3 extends AsyncTask<String, Void, String>
{

    String ret="";
    int checkStatus;
    Boolean exception=false;
    @Override
    protected String doInBackground(String... url) 
    {

        HttpURLConnection con = null;

        try 
          { 

            Log.i("RAE", "urlData"+url[0]);
            HttpURLConnection.setFollowRedirects(true);
             con = (HttpURLConnection) new URL(url[0]).openConnection();
                 con.setRequestMethod("POST");
              con.setConnectTimeout(20000);




          }


        catch (IOException e)
          {


            if(e.toString().contains("java.net.SocketTimeoutException:"))
            {



                return null;

            }



          }



    return ret;
    }
    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        Log.i("RAE"," Asyc finished");



}

score 0 · Accepted Answer · answered Dec 06 '14 at 05:05

0

you do something like this:

if((this.downloadNetTask != null) 
      && (this.downloadNetTask.getStatus() != AsyncTask.Status.FINISHED)){
        this.downloadNetTask.cancel(true);
}

Where downloadNetTask is instance of you async task. In your async task implement the following methods to do what you want when the task is cancelled.

protected void onCancelled(List<CompanyNseQuoteDataVO> result)

protected void onCancelled()

answered Dec 06 '14 at 05:05

Nazgul

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App is crashing and showing taskCancellation exception – Tarun Sharma Dec 06 '14 at 05:12
paste the stack trace here. – Nazgul Dec 06 '14 at 05:17
12-06 10:42:06.192: E/AndroidRuntime(31001): FATAL EXCEPTION: main 12-06 10:42:06.192: E/AndroidRuntime(31001): java.util.concurrent.CancellationException – Tarun Sharma Dec 06 '14 at 05:22
this is normal. when the runtime cancels pending tasks it throws a CancellationException. Check to make sure your asynch task finishes or not. – Nazgul Dec 06 '14 at 05:26
how do i do that please . – Tarun Sharma Dec 06 '14 at 05:30
debug your code...add a System.out on onCancelk methods in your async task put breakpoints in oncancel method on the System.out statement. and when the code i gave above runs on your cancel button click the breakpoints in your async task should be hit. – Nazgul Dec 06 '14 at 05:32
on cancelled is never called but if the isCancelled is return true nad app crash – Tarun Sharma Dec 06 '14 at 05:42

score 0 · Answer 2 · answered Dec 06 '14 at 05:07

The thing is that AsyncTask.cancel() call only calls the onCancel function in your task. This is where you want to handle the cancel request.

Here is a small task I use to trigger an update method

private class SomeTask extends AsyncTask<Void, Void, Void> {

        private boolean running = true;

        @Override
        protected void onCancelled() {
            running = false;
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
            onUpdate();
        }

        @Override
        protected Void doInBackground(Void... params) {
             while(running) {
                 publishProgress();
             }
             return null;
        }
     }

Or you can check your task like below.

protected Object doInBackground(Object... x) {
    while (/* condition */) {
      // work...
      if (isCancelled()) 
          break;
      }
    return null;
 }

how to stop a running async task?

2 Answers2