Can't see ProgressDialog while AsyncTask run in background

Question

I use AsyncTask in my App for download a url. I use a ProgressDialog on onPreExecute() for waiting. But I cant see ProgressDialog while process finish and i see it for a moment. want to see it while downloading not after that. can any one help me. thanks my code is like this:

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

    @Override
    protected void onPreExecute() {
        // Showing progress dialog before sending http request
        pDialog = new ProgressDialog(SingleMenuItemActivity.this);
        pDialog.setMessage("Please Wait ...");
        pDialog.isIndeterminate();
        pDialog.setCancelable(false);
        pDialog.show();
    }

    protected Void doInBackground(Void... unused) {
        runOnUiThread(new Runnable() {
            public void run() {

           // do something for downloading

        }
        });

        return (null);
    }


    protected void onPostExecute(Void unused) {
        // closing progress dialog
        pDialog.dismiss();
    }
}

The *whole point* of `doInBackground` is *NOT* to do it on the UI thread. `runOnUiThread` is only for updating the UI from the background process, when necessary. — David Conrad, Sep 09 '14 at 19:44

score 1 · Answer 1 · answered Sep 09 '14 at 19:41

 runOnUiThread(new Runnable() {
            public void run() {
           // do something for downloading
        }

// do something for downloading, inside runOnUiThread, is wrong. runOnUiThread makes "do something for downloading" run on the UI Thread, and your application should crash for NetworkOnMainThreadException, you the app runs on a device with a version of android grater than GingerBread. Differently it will block the ui thread preventing him to draw your progress bar

score 1 · Answer 2 · answered Sep 09 '14 at 20:20

The problem is in

runOnUiThread(new Runnable() {

        public void run() {

       // do something for downloading

    }
    });

ProgressDialog will not update if the UI thread is still busy. There are many examples in SO for that. I don't understand why do you need UIthread. And as a rule of thumb - if you need Progress dialog, you need to let run asynctask in background thread,as it always do.Read the document

http://developer.android.com/reference/android/os/AsyncTask.html

You can use the below example

http://www.androidhive.info/2012/01/android-json-parsing-tutorial/

user3144836 · Accepted Answer · 2014-09-09T20:01:29.893

Firstly notice the "@override" header attached to all the AsyncTask Implemented methods e.g.

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

    ProgressDialog pDialog;

    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        pDialog = new ProgressDialog(SingleMenuItemActivity.this);
        pDialog.setMessage("Please Wait ...");
        pDialog.isIndeterminate();
        pDialog.setCancelable(false);
        pDialog.show();
    }

    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        pDialog.cancel();

    }

}

Also Remove this from doInBackground unless you must do something on the UI.

runOnUiThread(new Runnable() {
        public void run() {

       // do something for downloading

    }
    });

You cannot do something for downloading on the runOnUiThread. doInBackground is meant for running background tasks like downloads etc. not visible to the UI.

Can't see ProgressDialog while AsyncTask run in background

3 Answers3

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