Closing JFrame with button inside JPanel not working

Question

I'm trying to close a JFrame from a button on a JPanel which is in my JFrame. I searched around and everything I tried doesn't work.

Here is my code in my JPanel:

public class warningPanel extends JPanel{

    //Klassen
    warning warningClass = new warning();
    loginGeneral loginGen = new loginGeneral();

    //Buttons
    buttons btnOk;

    //JLabels
    JLabel lblText;

    public warningPanel(){
        setLayout(null);

        this.setBounds(0, 0, 300, 150);

        btnOk = new button.buttons(110, 100, 60, 30, "000003006", "120090040", "255255255");
        btnOk.setText("OK");
        btnOk.setFont(new Font("default", Font.BOLD, 12));      

        add(btnOk);


        btnOk.addMouseListener(new MouseAdapter() {
            public void mouseClicked(MouseEvent e) {                
                warningClass.close();
            }

            public void mouseEntered(MouseEvent e) {
                btnOk.setBackground(loginGen.clGold);
            }

            public void mouseExited(MouseEvent e) {
                btnOk.setBackground(loginGen.clDarkBlue);
            }
        });

    }
}

Then here's my JFrame

public class warning extends JFrame{

    public void warningMessage(String warningtext){

        this.setSize(300, 150);
        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        this.setLocation(dim.width / 2 - this.getSize().width / 2, dim.height / 2 - this.getSize().height / 2);     
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.getContentPane().setBackground(new Color(1, 10, 19));
        this.setUndecorated(true);          

        this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);


        warningPanel panel = new warningPanel();
        panel.setOpaque(false);
        panel.setBounds(0, 0, 300, 150);

        this.setVisible(true);
        this.add(panel);
    }       

    public void close(){
        this.setVisible(false);
        this.dispose();
    }

}

I really have no idea why this doesn't work

Answer 1

To answer the question:

The instance of warning frame is not the same instance which is been displayed, meaning when you try and close it, it's not the one on the screen.

can't teach myself everything

Okay, a little lesson then ;)

What responsibility does your warningPanel have to close the window (or change the window at all)? None. It's only responsibility is to present information from your program to the user and get information from the user for your program.

I've lost count of the situations where I've developed, had a colleague develop or wanted to use a 3rd party component, which is been presented in a dialog in a large UI and had it contain the "okay" and "cancel" buttons ... well, so much for reuse :P

In most cases, it's not the responsibility of the component (warningPanel in your case) to even deal with these things. Let it focus on the single job it has to do, that's probably hard enough.

So, in your case warningPanel does one job, shows a message...

public class WarningPanel extends JPanel {

    //JLabels
    private JLabel lblText;

    public WarningPanel(String text) {
        setLayout(new GridBagLayout());
        add(new JLabel(text));
    }
}

That's it.

Every now and again, I might have a special case, where it's obvious that the panel should be shown in a dialog, when this occurs, I usually provide some utility method to generate the dialog and wrap up the management into a simple to use method, for example...

public class WarningPanel extends JPanel {

    //JLabels
    private JLabel lblText;

    public WarningPanel(String text) {
        setLayout(new GridBagLayout());
        add(new JLabel(text));
    }

    public enum DialogAction {
        OK, CANCEL, CLOSED
    }

    public static DialogAction showDialog(JComponent parent, String title, String message) {
        JDialog dialog = new JDialog(parent == null ? null : SwingUtilities.windowForComponent(parent));
        dialog.setTitle(title);
        WarningPanel pane = new WarningPanel(message);
        pane.setBorder(new EmptyBorder(4, 4, 4, 4));
        dialog.add(pane);

        JPanel buttonPane = new JPanel(new GridBagLayout());
        buttonPane.setBorder(new EmptyBorder(4, 4, 4, 4));

        State state = new State();

        JButton okBtn = new JButton("Ok");
        JButton cancelBtn = new JButton("Cancel");

        buttonPane.add(okBtn);
        buttonPane.add(cancelBtn);

        dialog.add(buttonPane, BorderLayout.SOUTH);

        DialogAction action = DialogAction.CLOSED;

        okBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                state.setState(DialogAction.OK);
                dialog.dispose();
            }
        });
        cancelBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                state.setState(DialogAction.CANCEL);
                dialog.dispose();
            }
        });

        dialog.pack();
        dialog.setLocationRelativeTo(parent);
        dialog.setVisible(true);

        return state.getState();
    }
}

Which allows you to use it something like this...

switch (WarningPanel.showDialog(null, "Warning", "Something wicked this way comes")) {
    case OK:
        // Everything is okay
        break;
    case CANCEL:
        // User cancelled
    case CLOSED:
        // Window was closed
        break;

}

Now, this is a demonstration of an idea, personally, I typically fall back to JOptionPane as it basically does the same thing

You might want to have a look at:

• How to Use Buttons, Check Boxes, and Radio Buttons
• How to use ActionListeners
• Code Conventions for the Java Programming Language