Android: Jumping effect of Status Bar

I have a problem with my app. I use the full screen option like so:

public void setFullscreen() {
    requestWindowFeature(Window.FEATURE_NO_TITLE);

    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
        WindowManager.LayoutParams.FLAG_FULLSCREEN);
}

But, later during the game, when I show the AlertDialog for Help / Info, the status bar comes back for a fraction of a second and disappears again creating a flashing or jumping effect. Also, the Dialog itself is not centered as it should, almost as if it thought there was a status bar.

Here is how I display the dialog:

protected Dialog onCreateDialog(int id) {
TextView tv;

switch (id) {
case MENU_HELP:
       tv = new TextView(this);
                   tv.setText(R.strings.help_msg);

       return new AlertDialog.Builder(BlackJackView.this)
       .setIcon(android.R.drawable.ic_menu_help)
       .setTitle("How开发者_运维问答-To")
       .setView(tv)
       .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int whichButton) {
                          /* User clicked OK so do some stuff */
                   }
       })
       .create();
  }

  ………

  }
  return null;
}

Does anyone know what may be causing this appearing / disappearing? How do I make it stop this jumping behavior?

Thanks for all your help.

Simply set dialog's window to fullscreen too

Dialog mPreviewDialog = new Dialog(this);

Window dialog_window = mPreviewDialog.getWindow();
dialog_window.setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);  
mPreviewDialog.show()

It fixes the blinking of status bar.