在另一个类中添加组件时，JPanel不会更新

Question

我对Java Swing还很陌生，遇到了一些问题。

public class Main {

private static void createAndShowGUI() {
    //Create and set up the window.
    JFrame frame = new JFrame("MathMaker");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Create the menu bar.  Make it have a green background.
    //MainToolBar mainTB = new MainToolBar();
    MainPanel mainPanel = new MainPanel();

    frame.getContentPane().add(mainPanel.getGUI(), BorderLayout.CENTER);
    frame.pack();
    frame.setVisible(true);
}

public static void main(String[] args) {
    //Schedule a job for the event-dispatching thread:
    //creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI();
        }
    });
}

}

public class MainPanel implements ActionListener{
JPanel mPanel;
JToolBar mToolBar;
JButton addQuestion;
    public MainPanel() {
        mPanel = new JPanel(new BorderLayout());
        mToolBar = new JToolBar();
        addQuestion = new JButton("test");
}
                

Answer 1

您应该重新验证面板

@Override
public void actionPerformed(ActionEvent e) {
   JButton temp = new JButton("temp");
   mPanel.add(temp);
   mPanel.revalidate();
   mPanel.repaint();
}