CODEWITHSUNDEEP
androidandroid-asynctask
melvintcs
melvintcs

Reputation: 551

asynctask cancel onpostexecute

i have a try and catch in "doInBackground", i dont wan the code be run the onPostExecute if the apps execute catch method in "doInBackground". code as below: 

public class DownloadFileAsync extends AsyncTask<String, Integer, Void> {
        @Override
        protected void onPreExecute(){
             super.onPreExecute();
     }

    @Override
    protected Void doInBackground(String... aurl) {
        try{
           //some code, jump to onPostexecute after complete
        }
        catch{
            //some code, don't do onPostExecute after complete
        }
        return null;

        }

    @Override
    protected void onProgressUpdate(Integer... progress) {          
    //some code
    }

    @Override
    protected void onPostExecute(Void unused) {
    //some code
    }
}

Upvotes: 1

Views: 2577

Answers (4)

Ian Warwick
Ian Warwick

Reputation: 4784

Use a Pair so you can return two results

Example, replace ANYTHING with the type that you want to return:

public class DownloadFileAsync extends AsyncTask<String, Integer, Pair<Exception, ANYTHING> > {    
    @Override
    protected Pair<Exception, ANYTHING> doInBackground(String... aurl) {
        try{
           return new Pair<Exception, ANYTHING>(null, /* anything can go here */);

        }
        catch (Exception e) {
             return new Pair<Exception, ANYTHING>(e, null);
        }    
    }

    @Override
    protected void onPostExecute(Pair<Exception, ANYTHING> result) {
        // Evaluate the exception here
        if(result.first != null) {
            // an eror occured, do something about it
        }
    }
}

This way allows you to handle an exception in onPostExecute as well as get the result from result.second if everything went ok.

Upvotes: 1

Arun George
Arun George

Reputation: 18592

You may try using cancel(true) in doInBackground(). Try the following code:

protected Void doInBackground(String... aurl) {
    try{
       //some code, jump to onPostexecute after complete
    }
    catch{
        cancel(true);
    }
    return null;

    }

The official note on cancel()

Calling this method will result in onCancelled(Object) being invoked on the UI thread after doInBackground(Object[]) returns. Calling this method guarantees that onPostExecute(Object) is never invoked. After invoking this method, you should check the value returned by isCancelled() periodically from doInBackground(Object[]) to finish the task as early as possible.

Check this link for further details:

http://developer.android.com/reference/android/os/AsyncTask.html#cancel(boolean)

Upvotes: 6

AggelosK
AggelosK

Reputation: 4341

You can have a boolean variable in your AsyncTask and check for that variable. For example:

public class DownloadFileAsync extends AsyncTask<String, Integer, Void> {

 private boolean run_do_in_background = true;

    @Override
    protected void onPreExecute(){
         super.onPreExecute();
 }

@Override
protected Void doInBackground(String... aurl) {
    try{
       //some code, jump to onPostexecute after complete
    }
    catch{
        //some code, don't do onPostExecute after complete
        run_do_in_background = false;
    }
    return null;

    }

@Override
protected void onProgressUpdate(Integer... progress) {     

//some code
}

@Override
protected void onPostExecute(Void unused) {
 if(run_do_in_background) { //only if this is true will excecute the code in doInBackground
//some code
}
}
}

Upvotes: 1

user370305
user370305

Reputation: 109247

Return boolean data type from your doInBackground() to onPostExecute() of your AsyncTask. And check for its values what you want to do for success,

@Override
    protected boolean doInBackground(String... aurl) {
        try{
           //some code, jump to onPostexecute after complete

         return true;
        }
        catch{
            //some code, don't do onPostExecute after complete

        return false;
        }   
      }

and

@Override
    protected void onPostExecute(boolean flag) {
    if(flag)
     {
      //some code
     }
    }

Upvotes: 3

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