Java 类javax.swing.plaf.basic.DefaultMenuLayout 实例源码

public void installDefaults() {
    if (popupMenu.getLayout() == null || popupMenu.getLayout() instanceof UIResource) {
        popupMenu.setLayout(new DefaultMenuLayout(popupMenu, BoxLayout.Y_AXIS));
        popupMenu.setOpaque(false);
    }
    updateStyle(popupMenu);
}