Q:

How to implement the Progressdialog here?

I am saving the imae from drawing canvas.
It takes some seconds to geting save to the sdcard.
So, During the process of save i want to show the dialog that the Image getting save...
So how to implement the progress dialog for that ?
The code for Image save is as like below:
 case R.id.saveBtn:
            Toast.makeText(getApplicationContext(), "Save", Toast.LENGTH_SHORT).show();
            final Activity currentActivity  = this;
            Handler saveHandler = new Handler(){
                @Override
                public void handleMessage(Message msg) {
                    final AlertDialog alertDialog = new AlertDialog.Builder(currentActivity).create();
                    alertDialog.setTitle("Drawing App");
                    alertDialog.setMessage("Your drawing had been saved :)");
                    alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int which) {
                            return;
                        }
                    });
                    alertDialog.show();
                }
            } ;

           new ExportBitmapToFile(this,saveHandler, drawingSurface.getBitmap()).execute();

        break;

A:

Since you are using AsyncTask (ExportBitmapToFile) you can call ProgressDialog in preExecute() and dismiss it in postExecute method. There are no Handlers required to do this.
edit
class ExportBitmapToFile extends AsyncTask<...> {
    private ProgressDialog  m_progressDialog = null;
    .... 

    @Override
    protected void onPreExecute(){
        m_progressDialog = new ProgressDialog(m_context);
        m_progressDialog.setMessage("please wait...");
        m_progressDialog.setCancelable(false);
        m_progressDialog.show();
    }

    @Override
    protected void onPostExecute(HashMap<String, String> result){
        m_progressDialog.dismiss();
        //your alert dialog with message to user
        AlertDialog.Builder builder = new AlertDialog.Builder(currentActivity);
            builder.setTitle("Drawing App");
            builder.setMessage("Your drawing had been saved :)");
            builder.setButton("OK", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                    return;
                }
            });
        alertDialog = builder.create()
        alertDialog.show();
    } 
}

