如何在CodeName one中绘制透明笔触来显示背景？

public class TransparentComponent extends com.codename1.ui.Component {
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        
        // 设置透明笔触
        g.setAlpha(100); // 设置透明度，范围为0-255
        g.setColor(0x000000); // 设置笔触颜色
        
        // 绘制透明笔触
        g.drawLine(getX(), getY(), getX() + getWidth(), getY() + getHeight());
    }
}

Form form = new Form("My Form", new BorderLayout());
TransparentComponent transparentComponent = new TransparentComponent();
form.add(BorderLayout.CENTER, transparentComponent);