Well. Thanks. I knew it already, just was wondering. Anyway i created another file for Custom Button control. But now the buttons are created from custom class, doesn't show in the bottom of the screen, instead it is displaying top most place on the screen. Code is something like below ...
CustomControl buttonControl;
add(buttonControl = new CustomControl("Add", ButtonField.CONSUME_CLICK, 20) );
.................................................. ...........
.................................................. ...........
_container.add(mainVerticalManager);
this.add(_container);