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Question

I want a progress dialog saying "Please Wait" , while my code downloads and parses a xml file but the Progress Dialog is not going, it somehow getting stuck. I am using AsyncTask, downloading of xml file and parsing are done in the background thread, the code is working if i remove the progress dialog, but in that case you have to wait for about 4 sec to click my button that dynamically creates UI.

private class ParseXML extends AsyncTask<Integer, Integer, Document>{

private Context context;
    private Activity activity;
    private ProgressDialog pd;
    public ParseXML(Activity activity) {
        this.activity = activity;
        context = activity;
        pd = new ProgressDialog(context);
    }




    public void onPreExecute(){
        super.onPreExecute();
    /*  ProgressDialog pd=ProgressDialog.show(XML_PARSER.this,"","Please Wait");*/

    }


    @Override
protected Document doInBackground(Integer... params) {

     DocumentBuilderFactory dbf= DocumentBuilderFactory.newInstance();
    Document dom1=null;
    try {

        //InputStream is=getResources().openRawResource(R.raw.options);
        URL requestURL = new URL("my url");
        URLConnection connection = requestURL.openConnection();
        is = connection.getInputStream();


        DocumentBuilder db = dbf.newDocumentBuilder();
        dom1=db.parse(is);
        Log.i(TAG,"parsing done");

    }

    catch(ParserConfigurationException pce){
        pce.printStackTrace();
    }
    catch(SAXException se){
        se.printStackTrace();
    }
    catch(IOException ioe){
        ioe.printStackTrace();
    }


    ParseDocument(dom1); 



    return null;
    }           

    @Override
    public void onPostExecute(Document d){
        if(pd!=null && pd.isShowing()){
               pd.dismiss();
               }
        super.onPostExecute(d);

    }
}

Answer 1

1. Its always advisable to keep the UI work on UI thread, and Non-UI work on Non-UI thread, but from Android version HoneyComb it became a rule.

2. So as you are using AsyncTask , let you ProgressDialog start showing in the Dedicated UI thread , from the onCreate() method.

3. Then dismiss the ProgressDialog from onPostExecute() Method, which is again on the Dedicated UI thread.

Answer 2

You are making mistake here

 public void onPreExecute(){
  super.onPreExecute();
 /*  ProgressDialog pd=ProgressDialog.show(XML_PARSER.this,"","Please Wait");*/
  }

you are declaring ProgressDialog pd a local variable

and when control is coming to

@Override
    public void onPostExecute(Document d){
        if(pd!=null && pd.isShowing()){
               pd.dismiss();
               }
        super.onPostExecute(d);

    }

pd is null here as you have not initialize the global pd variable. that is why alert dialog is not being dismissed.

to make this work just make some changes in onPreExecute

public void onPreExecute(){
      super.onPreExecute();
       pd=ProgressDialog.show(XML_PARSER.this,"","Please Wait");
      }