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I am running a task in back ground, and returning a result out of it.The result is coming null as its returned before the async task completes.how can i resolve it

public Result CallServer(String zObjectNameP, String zMethodNameP, String QueryStringP)
{
 aResultM=new Result();
MainAynscTask asyncTask = new MainAynscTask();
try
{
asyncTask.execute(zObjectNameP,zMethodNameP,QueryStringP);
}
catch(Exception ex)
{

}
return aResultM;
}
nks
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  • Try this http://stackoverflow.com/questions/14253421/how-one-interface-can-be-used-for-different-background-android-tasks/14376233#14376233 – Pragnani Apr 01 '13 at 09:57

1 Answers1

1

The 4 steps When an asynchronous task is executed, the task goes through 4 steps:

  1. onPreExecute(), invoked on the UI thread before the task is executed. This step is normally used to setup the task, for instance by showing a progress bar in the user interface.

  2. doInBackground(Params...), invoked on the background thread immediately after onPreExecute() finishes executing. This step is used to perform background computation that can take a long time. The parameters of the asynchronous task are passed to this step. The result of the computation must be returned by this step and will be passed back to the last step. This step can also use publishProgress(Progress...) to publish one or more units of progress. These values are published on the UI thread, in the onProgressUpdate(Progress...) step.

  3. onProgressUpdate(Progress...), invoked on the UI thread after a call to publishProgress(Progress...). The timing of the execution is undefined. This method is used to display any form of progress in the user interface while the background computation is still executing. For instance, it can be used to animate a progress bar or show logs in a text field.

  4. onPostExecute(Result), invoked on the UI thread after the background computation finishes. The result of the background computation is passed to this step as a parameter.

Use a Handler

In your activity

mHandler = new Handler() { 
@Override public void handleMessage(Message msg) { 
  String s=(String)msg.obj;
  tv.setText("Result = "+s);

}
};

In your onPostexecute

protected void onPostExecute(String result)//result returned in doInbackground
{
pd.dismiss();
if(result != null)
 {
 Message msg=new Message();
 msg.obj=result.toString();
 mHandler.sendMessage(msg);
 }
}