Problems with exiting application

Hello,

I have been creating a GUI and there is an exit JButton that can be clicked and when it is clicked the screen disappears and I thought that the application had exited, but after running it a few times I noticed that my RAM had gone up to more than usual for what I have running on my system. So I opened up my task manager and noticed that there were many instances of javaw.exe running. I know one of them is eclipse and I guess that the others are from where I repeatedly test my application and it isn't closing like I thought it was when I click the exit JButton. If I use the windows close button I don't have the same problem, it only happens when I use the JButton to close. I guess that just by using setVisible(false); to set the visibility of the window to false is not enough and I need to find another command to actually exit rather than making it invisible. I'm sure one of you intelligent folk will see at a glance what iswrong. I'm still new to Java so I haven't got a clue what I should use instead.

Here is the code for the handler of the exit JButton.

Code:

---

exit.addActionListener(
        new ActionListener(){
                public void actionPerformed(ActionEvent e){
                        setVisible(false);
                }
        }
);

---

You're making the frame invisible but its still running.

Instead use:

Code:

---

System.exit(1);

---

I would call dispose() on the JFrame and be sure to set its setDefaultCloseOperation to whatever I desired for that window, JFrame.EXIT_ON_CLOSE if you desire to exit at the time of closing.

Thanks for getting back so quickly, just tested it and it works. no more excessive RAM usage :)

My thanks was for solarsonic but now I have a question for Fubarable.

so by calling dispose(); Java would automatically call the default close operation for that frame?

Quote:

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Originally Posted by JohnPringle83

My thanks was for solarsonic but now I have a question for Fubarable.

so by calling dispose(); Java would automatically call the default close operation for that frame?

---

Try it and see! :)

I have just tested dispose(); in place of System.exit(1); but it fails to terminate the process, only the frame disappears which is the same result that I had originally.

Quote:

---

Originally Posted by JohnPringle83

I have just tested dispose(); in place of System.exit(1); but it fails to terminate the process, only the frame disappears which is the same result that I had originally.

---

show the code with code tags so we can see. It works fine for me.

Calling System.exit() is fine for simple programs. But keep in mind that if you have any resources open (files, sockets, etc.) it would be better to have your close button call a method that closes everything down neatly. Likewise, write an event handler for clicks on the JFrame's close button and have it call that same method.

Here is the code for the login screen, as you can see, I have used both the System.exit(1); for the exit button and dispose(); for the cancel button.

Code:

---

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

public class LoginScreen extends JFrame {
        private JLabel usernamelabel = new JLabel("Enter your username:");
        private JTextField username = new JTextField(20);
        private JLabel passwordlabel = new JLabel("Enter your password:");
        private JPasswordField password = new JPasswordField(20);
        private JButton login = new JButton("Login");
        private JButton cancel = new JButton("Cancel");
        private JButton exit = new JButton("Exit");
       
        public LoginScreen(){
                super("Login");
                setLayout(new FlowLayout());
               
                add(usernamelabel);
                add(username);
                add(passwordlabel);
                add(password);
                add(login);
                add(cancel);
                add(exit);
               
                login.addActionListener(
                                new ActionListener(){
                                        public void actionPerformed(ActionEvent e){
                                                //You still need to build the login process
                                                JOptionPane.showMessageDialog(null, "You still need to build the login process");
                                        }
                                }
                );
               
                cancel.addActionListener(
                                new ActionListener(){
                                        public void actionPerformed(ActionEvent e){
                                                StartScreen startscreen = new StartScreen();
                                                startscreen.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                                                startscreen.setSize(240,75);
                                                startscreen.setLocationRelativeTo(null);
                                                startscreen.setVisible(true);
                                                dispose(); //???
                                        }
                                }
                );

                exit.addActionListener(
                                new ActionListener(){
                                        public void actionPerformed(ActionEvent e){
                                                System.exit(1);
                                        }
                                }
                );
        }
}

---

Hm, I would think that a login screen would be more of a dialog window rather than an application window. Something else would ask it to pop up, and if opened, nothing else in the application would be accessible. Then if the user presses exit, I would have the main application get this information from the login object, and then the main app would handle the exiting.

Would I do that by setting an exit variable to 1 when the exit button is clicked and then getting the main application to check to see if the login objects exit variable is set to 1? I'm still new to Java but it's slowly starting to sink in.

Quote:

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Originally Posted by JohnPringle83

Would I do that by setting an exit variable to 1 when the exit button is clicked and then getting the main application to check to see if the login objects exit variable is set to 1? I'm still new to Java but it's slowly starting to sink in.

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You could, but I would avoid so-called "magic numbers". You could steal some Java constants, for example I sometimes have used JOptionPane constants even when not using JOptionPanes, or I've created my own enums for something like this. For e.g.,

Code:

---

public enum LoginState {
  LOGIN, EXIT, CANCEL
}

---

Code:

---

public class LoginScreen2 extends JPanel {
  public static final LoginState DEFAULT_LOGIN_STATE = LoginState.CANCEL;
  private LoginState loginState = DEFAULT_LOGIN_STATE;
  private String userName;
  private char[] password;

  public LoginState getLoginState() {
      return loginState;
  }

  public String getUserName() {
      return userName;
  }

  public char[] getPassword() {
      return password;
  }

  // etc.....

}

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To be honest, that didn't really make much sense to me, but thanks for your help, I'm thinking I need to do a bit of research into enums. I did watch a couple of tutorials about enums on youtube but not enough to understand what you just did. It would be nice to get my knowledge of Java to the point where I know what to do to achieve almost everything. I'm off to learn enums.

peace out :)

Quote:

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Originally Posted by JohnPringle83

I have just tested dispose(); in place of System.exit(1); but it fails to terminate the process, only the frame disappears which is the same result that I had originally.

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It fails to terminate the process because you didn't follow fubarable's instructions "be sure to set its [the frame's] setDefaultCloseOperation to whatever you desire for that window, JFrame.EXIT_ON_CLOSE if you desire to exit at the time of closing".