Android show progress bar while image loading dynamically

In one of my project, I am loading images from the dynamic url. Now I need to show the loading dialogue still all the images loads. I am loading the images using the Async task. I am new to android. Please any one give me a little help

My code looks like.

TableLayout table = (TableLayout)findViewById(R.id.tableLayout_1);
        for(Integer i=0;i<2;i++){


            TableRow rowP = new TableRow(this);
            rowP.setBackgroundColor(Color.parseColor("#FFF000"));




            ImageView image = new ImageView(this);
            String ed="http://www.domain.com/image.jpg";
            image.setTag(ed);
            DownloadImagesTask td=new DownloadImagesTask();
            td.execute(image);

            rowP.addView(image);
            table.addView(rowP);
            }
        }


private class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {

    ImageView imageView = null;

    @Override
    protected Bitmap doInBackground(ImageView... imageViews) {
        this.imageView = imageViews[0];
        return download_Image((String)imageView.getTag());
    }

    @Override
    protected void onPostExecute(Bitmap result) {
        imageView.setImageBitmap(result);
    }

    private Bitmap download_Image(String url) {

        Bitmap bmp =null;
        try{
            URL ulrn = new URL(url);
            HttpURLConnection con = (HttpURLConnection)ulrn.openConnection();
            InputStream is = con.getInputStream();
            bmp = BitmapFactory.decodeStream(is);
            if (null != bmp)
                return bmp;

            }catch(Exception e){}
        return bmp;
    }
}

Thanks in advance

Edit

private class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {

        ImageView imageView = null;
        ProgressDialog dialog;
        Context context;

        public DownloadImagesTask(Context context) {
            this.context = context;
        }

        @Override
        protected Bitmap doInBackground(ImageView... imageViews) {
            this.imageView = imageViews[0];
            return download_Image((String)imageView.getTag());
        }

        @Override
        protected void onPostExecute(Bitmap result) {
            imageView.setImageBitmap(result);
            if (dialog != null)
                dialog.dismiss();
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            dialog = ProgressDialog.show(context, "Title","Message");
        }

        private Bitmap download_Image(String url) {

            Bitmap bmp =null;
            try{
                URL ulrn = new URL(url);
                HttpURLConnection con = (HttpURLConnection)ulrn.openConnection();
                InputStream is = con.getInputStream();
                bmp = BitmapFactory.decodeStream(is);
                if (null != bmp)
                    return bmp;

                }catch(Exception e){}
            return bmp;
        }
    }