Question

I have a problem which I don’t understand. I want to show a simple Progress Dialog in Android. So I created an AsyncTask and create the dialog in the constructor. I use the methods onPreExceution to initialise the dialog and the onPostExecute method I destory the dialog. So until now this looks total correct for me. But when I start the App on my Nexus 7 the dialog doesn’t show up till the job is done. So it shows up for a half of a second at the end of the job… What am I doing wrong?

Thank you for your help 😉

public class ParseHTMLCodeNew extends AsyncTask<String, Void, String> {
    ProgressDialog dialog;

    public ParseHTMLCodeNew(Context context) {
        dialog = new ProgressDialog(context);
    }

    @Override
    protected void onPreExecute() {
        //einrichten des Wartedialogs
        dialog.setTitle("Bitte warten!");
        dialog.setMessage("Die Kommentare werden vom Server geladen.");
        dialog.show();
    }

    @Override
    protected String doInBackground(String params) {
        InputStream is = null;
        String data = "";
        try
        {
            URL url = new URL( params[0] ); 
            is = url.openStream(); 
            data = new Scanner(is).useDelimiter("//html//").next(); 
        } 
        catch ( Exception e ) { 
            e.printStackTrace(); 
        } 
        return data;
    }

    @Override
    protected void onPostExecute(String result) {       
        //Dialog beenden RSS Feed ist fertig  geparst
        if (dialog != null && dialog.isShowing()) {
            dialog.dismiss();
        }        
    }
}

UPDATE

This is my new AsyncTask:

public class ParseHTMLCodeNew extends AsyncTask<String, String, String> {
ProgressDialog dialog;
private final OnCompleteTaskListener onCompleteTaskListener;

public interface OnCompleteTaskListener {
        void onComplete(String data);
}

public ParseHTMLCodeNew(Context context, OnCompleteTaskListener taskListener) {
    onCompleteTaskListener = taskListener;
    dialog = new ProgressDialog(context);
}


@Override
protected void onPreExecute() {

    //einrichten des Wartedialogs
    dialog.setTitle("Bitte warten!");
    dialog.setMessage("Die Kommentare werden vom Server geladen.");
    dialog.show();

}

@Override
protected String doInBackground(String... params) {
    InputStream is = null; 
    String data = "";
    try 
    { 
      URL url = new URL( params[0] ); 
      is = url.openStream(); 
      data = new Scanner(is).useDelimiter("//html//").next(); 
    } 
    catch ( Exception e ) { 
      e.printStackTrace(); 
    } 
    return data;
}

@Override
protected void onPostExecute(String result){

  onCompleteTaskListener.onComplete(result);

  //Dialog beenden RSS Feed ist fertig  geparst
  if (dialog != null && dialog.isShowing()) {
      dialog.dismiss();
  }




}
}

And i am calling it this way:

new ParseHTMLCodeNew(this,new OnCompleteTaskListener() {

        @Override
        public void onComplete(String data) {
            gData = data;

        }
    }).execute(url);

As i commented on your post, data has no value.

Answer 1

If you calling this code so:

String data = new ParseHTMLCodeNew(CommentActivity.this).execute(url).get();

Then you do not really see your dialogue because there is a blocking UI.
Method get() waits if necessary for the computation to complete, and then retrieves its result.

Call so:

new ParseHTMLCodeNew(CommentActivity.this).execute(url);

and the result of the work is handled directly in the AsyncTask.

If you need to transfer the data to the main thread, you should tell him that the task was completed.
Wat is the simple code, I just added OnCompleteTaskListener interface

public class ParseHTMLCodeNew extends AsyncTask<String, Void, String> {

    private final OnCompleteTaskListener onCompleteTaskListener;
    private ProgressDialog dialog;

    public interface OnCompleteTaskListener {
        void onComplete(String data);
    }

    public ParseHTMLCodeNew(Context context, OnCompleteTaskListener taskListener) {
        onCompleteTaskListener = taskListener;
        dialog = new ProgressDialog(context);
    }

    @Override
    protected void onPreExecute() {

        // einrichten des Wartedialogs
        dialog.setTitle("Bitte warten!");
        dialog.setMessage("Die Kommentare werden vom Server geladen.");
        dialog.show();

    }

    @Override
    protected String doInBackground(String... params) {
        StringBuilder sb = new StringBuilder();

        // your code here
        try {
            for (int i = 0; i < 100; i++) {
                Thread.sleep(100);
                sb.append(i);
            }

        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return sb.toString();
    }

    @Override
    protected void onPostExecute(String result) {

        // Dialog beenden RSS Feed ist fertig geparst
        if (dialog != null && dialog.isShowing()) {
            dialog.dismiss();
        }

        onCompleteTaskListener.onComplete(result);
    }
}

And the example of a call

new ParseHTMLCodeNew(this,new OnCompleteTaskListener() {

            @Override
            public void onComplete(String data) {
                Toast.makeText(CommentActivity.this, data, Toast.LENGTH_LONG).show();

            }
        }).execute("your_url");

Be careful, this code can produce errors when you rotate your Phone.
When Activity destroyed but task is performed:
– progress dialog will close and will not open again
– local variable to dialog or context is incorrect.

If the operation is performed for a long time can make it through the of the services?