Question

I am new to Java Swing. I am creating a frame with some components.

I have to close the frame and open another frame when the button is clicked. I had tried setVisible(false) but it only hides the frame, not closing it. When I use System.exit(0), it closed all the frames.

I had tried in another way, i.e. add all the components to panel, and add the panel at first. When the frame has to close I just remove those components in actionListener and add the other components for the corresponding next process.

My entire code is as follows:

package JavaApp;

import java.awt.Component;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.IllegalBlockSizeException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;


public class Login extends JFrame {

    public static JLabel labelUser;
    public static JLabel labelPass;
    public static JTextField textFieldUser;
    public static JPasswordField passwordField;
    public static JButton clear;
    public static JButton buttonLogin;
    public static JButton ChangePassword;
    public static JButton MasterKey;
    public static JButton AppKey;
    public static JPanel panelGnereate;
    public static JPanel panelLogin;
    public static JFrame frame;
    public static JLabel UserName;
    public static JTextField UserTxt;
    public static JButton GenerateKey;
    public static JPanel panelMaster;

    private static void designUI() {

        frame = new JFrame("Instalation");

        frame.setLayout(new GridLayout(2, 1));

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        panelLogin = new JPanel();
        panelLogin.setLayout(null);
        labelUser = new JLabel("Enter UserName");
        textFieldUser = new JTextField(10);
        labelPass = new JLabel("Enter Password");
        passwordField = new JPasswordField(10);
        buttonLogin = new JButton("Login");
        clear = new JButton("Cancel");
        panelLogin.add(buttonLogin);
        panelLogin.add(clear);
        panelLogin.add(labelUser);
        panelLogin.add(textFieldUser);
        panelLogin.add(labelPass);
        panelLogin.add(passwordField);
        textFieldUser.setBounds(200, 120, 100, 20);
        labelUser.setBounds(50, 120, 120, 20);
        labelPass.setBounds(50, 150, 120, 20);
        passwordField.setBounds(200, 150, 100, 20);
        buttonLogin.setBounds(70, 180, 100, 20);
        clear.setBounds(200, 180, 100, 20);
        buttonLogin.addActionListener(actionEvent);
        clear.addActionListener(actionEvent);
        frame.add(panelLogin);
        //Login frame ends...

        //Gnereate frame starts here..

        panelGnereate = new JPanel();
        panelGnereate.setLayout(null);
        ChangePassword = new JButton("Change Password");
        MasterKey = new JButton("Create Master Key");
        AppKey = new JButton("Create Application key");
        panelGnereate.add(ChangePassword);
        panelGnereate.add(MasterKey);
        panelGnereate.add(AppKey);
        ChangePassword.setBounds(150, 100, 200, 25);
        MasterKey.setBounds(150, 150, 200, 25);
        AppKey.setBounds(150, 200, 200, 25);

        ChangePassword.addActionListener(actionEvent);
        MasterKey.addActionListener(actionEvent);
        AppKey.addActionListener(actionEvent);
        //Gnerate Frame ends here..


        //MasterKey Generate Starts Here..

        panelMaster = new JPanel();
        panelMaster.setLayout(null);
        UserName = new JLabel("Text");
        UserTxt = new JTextField(20);
        GenerateKey = new JButton("Generate Key");
        panelMaster.add(UserName);
        panelMaster.add(UserTxt);
        panelMaster.add(GenerateKey);
        UserName.setBounds(150, 150, 50, 25);
        UserTxt.setBounds(220, 150, 100, 25);
        GenerateKey.setBounds(180, 180, 150, 25);
        GenerateKey.addActionListener(actionEvent);


        frame.setSize(500, 500);
        frame.setVisible(true);
    }


    public static void main(String args[]) {

         designUI();

    }
    private static ActionListener actionEvent = new ActionListener() {

        public void actionPerformed(ActionEvent e) {
            String action = e.getActionCommand();
            if ("Login".equals(action)) {
                System.out.println("Login action" + e.getActionCommand());
                if ("".equals(textFieldUser.getText()) || "".equals(passwordField.getText())) {
                    JOptionPane.showMessageDialog(null,
                            "Enter Both UserName and Password");

                } else if ("admin".equals(textFieldUser.getText()) && "admin".equals(passwordField.getText())) {


                    System.out.println("login value" + textFieldUser.getText() + "     " + passwordField.getText());
                    frame.remove(panelLogin);
                    frame.add(panelGnereate);
                    frame.setVisible(true);
                } else {
                    JOptionPane.showMessageDialog(null,
                            "Wrong Password");

                }
            } else if ("Cancel".equals(action)) {
                System.out.println(e.getActionCommand());
                System.exit(0);

            } else if ("Change Password".equals(action)) {

            } else if ("Create Master Key".equals(action)) {
                frame.remove(panelGnereate);
               frame.add(panelMaster);

                frame.setVisible(true);
            } else if ("Create Application key".equals(action)) {
                System.out.println("Message " + UserTxt.getText());

                frame.setVisible(false);
            }else if("Generate Key".equals(action))
            {
                try {
                    new GenerateTxt(UserTxt.getText());
                } catch (NoSuchAlgorithmException ex) {
                    Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
                } catch (IllegalBlockSizeException ex) {
                    Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
                } catch (IOException ex) {
                    Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
                }

                frame.remove(panelMaster);
                frame.add(panelGnereate);
                 frame.setVisible(true);
            }
        }
        ;

    };
}

It’s not working for throughout the process. When I click the master key it showing relevant textbox after clicking genearteKey it showing same panel not the previous one. But when I am moving the mouse over there it is showing the components of the both panels.

Answer 1

looking at your code, you’ll probably need something like this:

            if(frame == null)
                frame = new JFrame();
            else {
                //remove the previous JFrame
                frame.setVisible(false);
                frame.dispose();
                //create a new one
                frame = new JFrame();
            }

you’ll have to put this inside the actionperformed method so that the frame can be removed..
btw, it would be a gd idea to change your class variables from public to private, in accordance with good programming practice..

EDIT: To answer the “flickering” problem.
you’re accessing the swing component from outside the event thread. swing widgets arent generally thread safe. as such, u need to modify your main method:

public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            designUI();
        }
    });
}

also, refer to Swing component flickering when updated a lot for further queries.