Difficulties with dispalying progressdialog

Question

I need to display progrees dialog. It is quite simple, however I am absolutly required to wait untill asynctask will finish. That exopse some difficulties to me. To wait for completion of asynctask method .get() is used. But this method blocks my progress dialog. So, how can I unblock progressdialog with get or what can replace .get()?

I am calling operation in a following way:

Operation o = new Operation();
o.execute(params);
try {
            o.get();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ExecutionException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

class Operation

class Operation extends AsyncTask<String, Void, JSONObject> {
        ProgressDialog pd;
        Context con;

        @Override
        protected void onPreExecute() {
            pd = new ProgressDialog(app);
            pd.setOwnerActivity(app);
            pd.setTitle("Идет загрузка...");
            pd.setCancelable(true);
            pd.show();
        }

        @Override
        protected JSONObject doInBackground(String... option) {
            /*
            some job
            */

            return json;
        }

        @Override
        protected void onPostExecute(JSONObject result) {
            super.onPostExecute(result);
            pd.dismiss();

            /* 
            some job
            */
        }
    }

Answer 1

You might want to change your code to something like this. Wrap the code you want to run afterwards in a runnable and pass it to your async task.

 Runnable onEnd = new Runnable(){
    //code to run after the task has completed
 }
 Operation o = new Operation(onEnd);
 o.execute(params);

And here is the modified Operation class.

class Operation extends AsyncTask<String, Void, JSONObject> {
    ProgressDialog pd;
    Context con;
    Runnable afterwards = null;

    Operation(Runnable afterwards){
      this.afterwards  = afterwards ;
    }

    @Override
    protected void onPreExecute() {
        pd = new ProgressDialog(app);
        pd.setOwnerActivity(app);
        pd.setTitle("Идет загрузка...");
        pd.setCancelable(true);
        pd.show();
    }

    @Override
    protected JSONObject doInBackground(String... option) {
        /*
        some job
        */

        return json;
    }

    @Override
    protected void onPostExecute(JSONObject result) {
        super.onPostExecute(result);
        pd.dismiss();

        /* 
        some job
        */
        if (afterwards  != null)
           afterwards.run();
    }
}

Note the afterwards.run() in onPostExecute.

Answer 2

try to use this way

private ProgressDialog dialog=null;

     @Override
            protected void onPreExecute() {
                dialog = ProgressDialog.show(this, "", "Please! Wait...",true);
            }


            @Override
            protected void onPostExecute(JSONObject result) {
                super.onPostExecute(result);
                dialog.dismiss();
               // use here code
            }

Answer 3

Don't use .get() as you have seen it blocks the UI. You can use getStatus() if you need to check if the task is finished. Removing .get() should allow your ProgressDialog to show. If you have code that must wait until the AsyncTask is finished then put it in onPostExecute() or call a function from there

If you need to reference something in the MainActivity from the AsyncTask after it has finished, simply create a constructor to take a reference of your Activity and pass context to your constructor

Operation o = new Operation(this);

and reference it in constructor

lass Operation extends AsyncTask<String, Void, JSONObject> {
    ProgressDialog pd;
    Context con;
    Activity act;

  public Operator(Activity curAct)
  {
      act = curAct;   // can use this reference to access methods in your Activity  
   }