您可以将JPanel添加到actionPerformed类吗？

Question

我是新来的，所以我真的瞎了。因此，我想在单击开始按钮后添加一个移动球。但是我不知道如何。下面的代码是我遇到的问题。特别是在公共场合无效Actionperformed（）。

我也尝试了几种方法来达到预期的结果，但我一无所获。 这是代码：

public static JFrame f1;
public JFrame f2;
public JLabel lstr, labu;
public JPanel screen;
public JButton btstr, btabu;
public Timer t;

public menu() {
    f1.add(lstr = createLabel("Welcome to Quizzer Ball!", 227, 25, 400, 30));
    f1.add(btstr = createButton("Start", 250, 50, 100, 30 ));
    f1.add(btabu = createButton("About Us", 250, 90, 100, 30 ));

    btstr.addActionListener(this);
    btabu.addActionListener(this);
}
public JButton createButton(String string, int i, int j, int k, int l) {
    // TODO Auto-generated method stub

    JButton btn = new JButton(string);
    btn.setBounds(i, j, k, l);

    return btn;
}

public JLabel createLabel(String string, int i, int j, int k, int l) {
    // TODO Auto-generated method stub

    JLabel lb = new JLabel(string);
    lb.setBounds(i, j, k, l);

    return lb;
}
game gamescrn = new game();
public JPanel createPanel(String string, int i, int j, int k, int l) {
    // TODO Auto-generated method stub

    JPanel panel = new JPanel();
    panel.setBounds(i, j, k, l);
    btstr.setVisible(false);
    btabu.setVisible(false);
    lstr.setVisible(false);
    gamescrn.paint(getGraphics());

    return screen;
}
public static void main (String[]args) {
    f1 = new JFrame ("Quizzer Ball");
    f1.setLayout(null);
    f1.setSize(600, 400);
    f1.setVisible(true);
    new menu();
}
@Override
public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    if(e.getSource()==btstr) {
        createPanel();
    }
    }
}      

game.java在哪里

    Timer t = new Timer(10, this);
    int x = 0, y = 0, velX = 2, velY = 2;

    Random r = new Random();

    public Ball ball = new Ball(this);

    public void paint (Graphics g) {
    super.paint(g);
    g.setColor(Color.red);
    ball.paint(g);

    t.start();
    }


public void move() {
    ball.move();
}

    class Ball{
    public int x = r.nextInt(540), y = r.nextInt(320), velX=2, velY=2;
    public game anim;

    public Ball(game anim) {
        this.anim = anim;
    }
    public void move() {
        if (x<0 || x>540) {
            velX = -velX;
        }
        if (y<0||y>320) {
            velY = -velY;
        }
        x += velX;
        y += velY;

    }

    public void paint (Graphics g) {
        g.fillOval(x, y, 40, 40);
    }
}


@Override
public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    move();
    repaint();
}

}

我希望createPanel代码段位于actionPerformed内部。但它不会首先运行。