Java Swing-为什么我的第一个窗口没有布置/关闭？

Question

So I'm creating an application. I want main to initialize a login window, which I've done. And for now I want the login window to close whenever I click on the button, and when it closes, a new window (called MainWindow) opens with different buttons/info/text.

All these classes are separate, but in the same package.

The problem is: The main window opens when I click login, however the login window doesn't terminate/close.

My main method, from which I call the login window:

import javax.swing.*;

public class Main {

    // Display Login Window
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            new LoginWindow();
            LoginWindow.createAndShowLoginGUI();
        });
    }
}

My login window class:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class LoginWindow extends JFrame implements ActionListener {

    public void prepareLoginGUI() {

        // Frame with GridBagLayout
        JFrame loginFrame = new JFrame("Login Window");
        loginFrame.setSize(1200, 800);
        loginFrame.setLayout(new GridBagLayout());


        // Button for logging in, with respective GridBagConstraint
        // setFocusable is set to false to take out the border around the text
        JButton loginButton = new JButton("Login");
        loginButton.addActionListener(this::actionPerformed);
        loginButton.setActionCommand("Open");
        GridBagConstraints lButtonC = new GridBagConstraints();
        loginButton.setFocusable(false);


        // Username text-field and JLabel with respective GridBagConstraints
        JTextField tfUsername = new JTextField(15);
        GridBagConstraints tfUserC = new GridBagConstraints();
        JLabel txtUser = new JLabel("Username: ");
        GridBagConstraints txtUserC = new GridBagConstraints();


        // Password text-field and JLabel with respective GridBagConstraints
        JPasswordField tfPassword = new JPasswordField(15);
        GridBagConstraints tfPassC = new GridBagConstraints();
        JLabel txtPassword = new JLabel("Password: ");
        GridBagConstraints txtPassC = new GridBagConstraints();


        // Add all components to the JFrame
        // Making sure to add the text before the text-fields
        loginFrame.add(txtUser, txtUserC);
        loginFrame.add(tfUsername, tfUserC);
        loginFrame.add(txtPassword, txtPassC);
        loginFrame.add(tfPassword, tfPassC);
        loginFrame.add(loginButton, lButtonC);

        // Show and set close parameters
        loginFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        loginFrame.setVisible(true);
    }

    // Instructions for when the login button is clicked
    // Close this window, if button == open, which it does
    @Override
    public void actionPerformed(ActionEvent e) {
        String cmd = e.getActionCommand();
        if (cmd.equals("Open")) {
            this.dispose();
            this.setVisible(false);
            new MainWindow();
            MainWindow.createAndShowMainWGUI();
        }
    }

    // Callable from Main class
    public static void createAndShowLoginGUI() {
        LoginWindow loginW = new LoginWindow();
        loginW.prepareLoginGUI();

    }

}

My Main Window Class:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class MainWindow extends JFrame implements ActionListener {

    public void prepareMainWGUI(){
        // Frame with GridBagLayout
        JFrame loginFrame = new JFrame("Main Window");
        loginFrame.setSize(1200, 800);
        loginFrame.setLayout(new GridBagLayout());


        // Username text-field and JLabel with respective GridBagConstraints
        JLabel txtUser = new JLabel("It worked!");
        GridBagConstraints txtUserC = new GridBagConstraints();

        loginFrame.add(txtUser, txtUserC);

        loginFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        loginFrame.setVisible(true);
    }

    // Callable from Main class
    public static void createAndShowMainWGUI() {
        MainWindow mainWind = new MainWindow();
        mainWind.prepareMainWGUI();
    }

}

If you use this code, when the main window opens, the login window will be right behind it.

Answer 1

You can use when pressing button

System.exit(0);

This will terminate your application. To close one window use(if you have open multiple windows) without affecting to others,

setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE)

Then, to open new one,

new frameName().setvisible(true);

Example:

JButton closeButton = new JButton("Close");

closeButton .addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e)
    {
        this.dispose();//current(close only this) frame
        new frameName().setvisible(true);
    }
});

Take a look at this question .

UPDATE:

In below line you have extends JFrame but you didnot use it.

public class LoginWindow extends JFrame implements ActionListener {

Rather than that you have create new object from JFrame

JFrame loginFrame = new JFrame("Login Window");

All the component you are adding to the loginFrame . But when actionPerformed trying to this.dispose() , since you are not using extended JFrame nothing will happen.

Solution:

Declare your JFrame as a instance variable:

public class LoginWindow implements ActionListener {
    JFrame loginFrame;
    public void prepareLoginGUI() {

Then change,

this.dispose();

To:

loginFrame.dispose();

In this this.dispose(); call to the extended JFrame , no effect for your JFrame object( loginForm ).

And one last thing, make sure to remove extends JFrame . Because you are not doing anything with extended JFrame . Read this post about extended JFrame .