看看其他答案,我完全按照他们的说法,但我只是不断收到nullPointerException错误。我有4个类,下面的2个,一个GUI类和主菜单类。主要管理卡布局,我希望Insert类中的按钮将“活动”卡更改为主菜单类。Java,改变另一个类的活动卡
主营:
public class Main extends JPanel implements ChooserListener{
MainMenu mm;
Insert InsertCustomer;
public JPanel mPanel;
CardLayout cl;
private String c;
public Main(){
super();
//add mPanel, set to CardLayout and add the Main
mPanel = new JPanel();
this.add(mPanel);
cl = new CardLayout();
mPanel.setLayout(cl);
//add classes
mm = new MainMenu(this);
InsertCustomer = new Insert();
//add classes to mPanel
mPanel.add(mm, "mm");
mPanel.add(InsertCustomer, "InsertCustomer");
}
public void tell(Object o) {
c = o.toString();
cl.show(mPanel, c);
}
public void swapView(String key) {
CardLayout cl = (CardLayout)(mPanel.getLayout());
cl.show(mPanel, key);
}
}
插入:
public class Insert extends JPanel{
private JButton logoutbutton;
private LogoutListener lListener;
public Insert() {
super();
//BUTTONS
//logout button
JButton logoutbutton = new JButton("Main Menu");
this.add(logoutbutton);
lListener = new LogoutListener(null);
logoutbutton.addActionListener(lListener);
}
private class LogoutListener implements ActionListener{
private Main main;
public LogoutListener(Main main){
this.main = main;
}
public void actionPerformed(ActionEvent e) {
main.swapView("mm");
}
}
}
你可以在这里添加stackTrace吗? – ItachiUchiha
你在哪里有NullPointerException? –
一个非常简单的空指针异常。这个问题不可能在将来帮助任何人。 –