java - (JAVA) 添加新组件时如何实现滚动？

Question

如果我添加新组件，滚动 Pane 不会更新。我可以在不创建新的 JScrollPane 的情况下更新它吗？

 public void start(){
        getBox_Topics().setBorder(new TitledBorder(new EtchedBorder(),"Topics of vote"));
        add(new JScrollPane(getBox_Topics(),
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_NEVER));
        pack();
        setHandler(new ClientHandler_Thread(this));
        getHandler().start();
        setVisible(true);
    }

按钮在 Box 中添加新组件:

Answer 1

Box/JPanel 必须是固定大小。或者它必须有MaximumSize。

public void start(){
    getBox_Topics().setBorder(new TitledBorder(new EtchedBorder(),"Topics of vote"));
    setScrollPane(new JScrollPane(getBox_Topics()));
    add(getScrollPane());
    getScrollPane().setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
    getBox_Topics().addContainerListener(new ContainerListener() {
        @Override
        public void componentAdded(ContainerEvent containerEvent) {
            getScrollPane().revalidate();
            getScrollPane().repaint();
        }

        @Override
        public void componentRemoved(ContainerEvent containerEvent) {

        }
    });
    pack();
    setHandler(new ClientHandler_Thread(this));
    getHandler().start();
    setVisible(true);
}