Question

我正在尝试在添加其他选项时将组件从JLabel更改为JComboBox，但由于某种原因，该面板未更新。

SSCCE：

public class SwitchComponent {
    public static void main(String[] args) { 
        JPanel panel = new JPanel();
        JComponent component = new JLabel("This is a test");

        panel.add(component);

        JComboBox<String> comboBox = new JComboBox<String>();
        comboBox.addItem("Testing..");
        comboBox.addItem("1.. 2.. 3..");

        component = comboBox;

        // I have tried with only one of the below lines and without any also...
        // Doesn't seem to have an effect.
        // I've also tried invoking the below methods on the panel instead.
        component.revalidate();
        component.repaint();

        JOptionPane.showConfirmDialog(null, panel, "Test",
                                      JOptionPane.OK_OPTION,
                                      JOptionPane.PLAIN_MESSAGE);
    }
}

为什么会这样？不应panel引用component，以便对component的任何更改都通过panel反映出来了吗？

当组件发生变化时，我真的必须完全重新组装面板吗？

Answer 1

当点击JOptionPane上的YES / NO按钮时，JOptionPane将关闭。

我们需要再次将JComboBox添加到Panel，并使用JOptionPane在您的代码中再次显示Panel。

试试这个：

public class SwitchComponent {
public static void main(String[] args) { 
    JPanel panel = new JPanel();
    JComponent component = new JLabel("This is a test");

    panel.add(component);

    JOptionPane.showConfirmDialog(null, panel, "Test",
                                  JOptionPane.OK_OPTION,
                                  JOptionPane.PLAIN_MESSAGE);

    panel.remove(component);

    JComboBox<String> comboBox = new JComboBox<String>();
    comboBox.addItem("Testing..");
    comboBox.addItem("1.. 2.. 3..");
    panel.add(comboBox);

    // I have tried with only one of the below lines and without any also...
    // Doesn't seem to have an effect.
    // I've also tried invoking the below methods on the panel instead.
    panel.revalidate();
    panel.repaint();

    JOptionPane.showConfirmDialog(null, panel, "Test",
            JOptionPane.OK_OPTION,
            JOptionPane.PLAIN_MESSAGE);

}
}

Answer 2

即。标签可能是三个系列中的第二个，当组件更改为组合框时，我希望组合框保持第二。因此，为什么我试图改变参考

使用Card Layout。它将替换同一位置的组件。

Java更改现有组件

2 个答案: