blackberry自定义field的滚动条？

                sv = new ScrollView();
Drawable element = new Drawable() {

public void paint(Graphics graphics) {
graphics.drawText("test", 1, 1);
graphics.drawLine(15, 15, 15, 1815);
graphics.drawRect(100, 100, 200, 1200);
}
};
sv.addDrawableElement(element);

VerticalFieldManager manager = new VerticalFieldManager(
VerticalFieldManager.VERTICAL_SCROLL
| VerticalFieldManager.VERTICAL_SCROLLBAR);
manager.add(sv);

怎么样实现自定义field的滚动条呢？ --------------------编程问答-------------------- 是进度条不？

补充：移动开发 ,  BlackBerry