Android AsyncTask return value

Question

final Dialog Alert_Dialog = new Dialog(MainList.this);
Alert_Dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
Alert_Dialog.setContentView(R.layout.alert_dialog_progressbar);
((TextView)Alert_Dialog.findViewById(R.id.txtMessage)).setText(R.string.please_wait_);
Alert_Dialog.setCancelable(false);
Alert_Dialog.show();
((Button) Alert_Dialog.findViewById(R.id.btnCancel)).setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
    Alert_Dialog.cancel();
   }
});

Then callin AsynTask like :

String res="";
try{
    SendingWebPageTask sendMaster=new SendingWebPageTask();
    res=sendMaster.execute(UrlMaster).get();
}catch (Exception e) {
e.printStackTrace();
}

i am returning value which url responding me on the base of responce i am calling second url but the problem it that when i am returning value from async task in this way it will not display an dialogbox and it will hang device till asynTask cannot complete its task so can any one help me.

so anyother way to display progress bar and return value from AsyncTask? — PankajAndroid, May 23 '13 at 10:52
`so anyother way to display progress bar and return value from AsyncTask` isn't a solution sir? — Pankaj Kumar, May 23 '13 at 11:23
:D ok. I would suggest you to call asynctask from dialog, (at the same place where you canceled the dialog) and then update value of `res` on postexecute of asyntask...... now this is not a joke... — Pankaj Kumar, May 23 '13 at 11:31

ρяσѕρєя K · Answer 1 · 2013-05-23T11:00:08.760

4

In here:

res=sendMaster.execute(UrlMaster).get(); //<<<

you are calling AsyncTask.get() method on UI Thread instead of on other thread so this will freeze UI until doInBackground execution is not completed and then get result back to main ui Thread.

Option 1#

you will need to use onPostExecute for updating UI when doInBackground execution complete because onPostExecute always called on UI thread. for showing ProgressDialog you can use onPreExecute() which called before stating background task

Option 2#

call AsyncTask.get() inside a Thread for getting results from doInBackground and use Activity.runOnUiThread for updating UI from non UI Thread

edited May 23 '13 at 11:00

answered May 23 '13 at 10:54

ρяσѕρєя K

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Thanks for your reply but on the resulet of 1st async task i am calling second url in this case i have to use .get to return value if i cannot use .get() then in second url it will pass null value – PankajAndroid May 23 '13 at 11:01
@Pankaj : ok then see second Option 2 in my answer – ρяσѕρєя K May 23 '13 at 11:02
ok but i cannot do this with AsyncTask? becasuse in Runnable UiThread there is chanse of ANR. – PankajAndroid May 23 '13 at 11:06

Houcine · Answer 2 · 2013-05-23T11:04:28.170

Try this :

 class SendingWebPageTask extends AsyncTask<String, Void, String>
        {
                private Dialog alertDialog;
                private boolean shouldCallTheSecondURL = false;

                public SendingWebPageTask(boolean shouldCallSecondURL) {
                     this.shouldCallSecondURL = shouldCallSecondURL;
                }
            @Override
            protected void onPreExecute() {
               alertDialog = new Dialog(MainList.this);
    alertDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
    alertDialog.setContentView(R.layout.alert_dialog_progressbar);
    ((TextView)alertDialog.findViewById(R.id.txtMessage)).setText(R.string.please_wait_);
    alertDialog.setCancelable(false);
    alertDialog.show();
    ((Button) alertDialog.findViewById(R.id.btnCancel)).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
        alertDialog.dismiss();
       }
    });
            }

            @Override
            protected String doInBackground(String... params) {
                //TODO your code in background...
                            return result;//result is in String format
            }

            @Override
            protected void onPostExecute(String result) {
                            //dismiss the alertDialog after the task finish his background work
                            alertDialog.dismiss();
                super.onPostExecute(result);
                Log.d("SendingWebPageTask", "result task : "+result);
                            String secondUrl = result;
                            if(shouldCallSecondURL)
                                new SendingWebPageTask(false).execute(secondUrl); 
            }
        }

for the fisrt call of your AsyncTask :

SendingWebPageTask sendMaster=new SendingWebPageTask(true);//passing true , so the asyncTask will launch another asynctask for the secondURL retreived from onPostExecute()
sendMaster.execute(UrlMaster);

i had tried this also but on the base of calling first url i am returning value and on return value i am calling second url in this way i have to return value from asynk task so this solution doesnt work in my case — PankajAndroid, May 23 '13 at 10:59
so , in the `onPostExecute()` method you can execute your `AsyncTask` again, and pass to it the second url that you got from the first call of the asyncTask. see my edits — Houcine, May 23 '13 at 11:00
i am continiosly sending data to web server when i call url it will give me reply if it is successfuly store then i am calling second or third url in this way how can i use onPostExecute()?? — PankajAndroid, May 23 '13 at 11:03
Thanksf for this but i have more data inshort i am retriving data from my sqlite and storing on webserver so when i store 1st data it will respond me. on the base of respoce i am sending next to next data — PankajAndroid, May 23 '13 at 11:09
all that treatment you can do it into onPostExecute, you can test your result and check if you should execute the AsyncTask again ,with the next data to send to server, or not — Houcine, May 23 '13 at 11:14

Android AsyncTask return value

2 Answers2