从JButton问题打开一个新的类（JFrame）

Question

just a disclaimer: I already checked most of Stack Overflow and couldn't find an answer on the website. I also asked some nice people on Reddit, but only fixed it halfway through.

So, I am trying the create a GUI application and I am new to the Java language (very, very new - so there is a big chance I am making a rookie mistake). I already designed my interface for my 'StartScreen' and I wanted to make button1 to open my second class ('NewUsers').

I was using the GUI Editor and I think this is probably the cause of my problems, as an answer to my question online I just saw people add

this.dispose();
new JFrame().setVisible(true);

This doesn't work on me however. I managed to fix it until a certain point and now I am able to close the frame on a click, but I still can't figure out how to open another frame from the button :(. Here is my code for Frame1('StartScreen'). Frame2 is just an empty window for now, but it's for testing purposes.

 import javax.swing.*; import java.awt.*; import java.awt.event.ActionEvent; public class StartScreen { private final JFrame frame; private JButton newUserButton; private JButton existingUserButton; private JButton nonUserBookingButton; private JPanel panell; public StartScreen() { this.frame = new JFrame("StartScreen"); frame.setContentPane(panell); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.pack(); frame.setVisible(true); newUserButton.addActionListener(this::onNewUserClicked); } public static void newuserscall () { NewUsers newuserscall = new NewUsers(); } private void onNewUserClicked(ActionEvent event) { frame.setVisible(false); } public static void main(String[] args) { new StartScreen(); } { // GUI initializer generated by IntelliJ IDEA GUI Designer // >>> IMPORTANT!! <<< // DO NOT EDIT OR ADD ANY CODE HERE! $$$setupUI$$$(); } /** * Method generated by IntelliJ IDEA GUI Designer * >>> IMPORTANT!! <<< * DO NOT edit this method OR call it in your code! * * @noinspection ALL */ private void $$$setupUI$$$() { panell = new JPanel(); panell.setLayout(new GridBagLayout()); panell.setPreferredSize(new Dimension(600, 400)); final JPanel spacer1 = new JPanel(); GridBagConstraints gbc; gbc = new GridBagConstraints(); gbc.gridx = 0; gbc.gridy = 4; gbc.fill = GridBagConstraints.VERTICAL; gbc.insets = new Insets(30, 0, 0, 0); panell.add(spacer1, gbc); newUserButton = new JButton(); newUserButton.setText("Button"); gbc = new GridBagConstraints(); gbc.gridx = 1; gbc.gridy = 2; gbc.gridwidth = 2; gbc.fill = GridBagConstraints.BOTH; panell.add(newUserButton, gbc); existingUserButton = new JButton(); existingUserButton.setText("Button"); gbc = new GridBagConstraints(); gbc.gridx = 1; gbc.gridy = 4; gbc.gridwidth = 2; gbc.fill = GridBagConstraints.BOTH; panell.add(existingUserButton, gbc); nonUserBookingButton = new JButton(); nonUserBookingButton.setText("Button"); gbc = new GridBagConstraints(); gbc.gridx = 1; gbc.gridy = 6; gbc.gridwidth = 2; gbc.fill = GridBagConstraints.BOTH; panell.add(nonUserBookingButton, gbc); final JPanel spacer2 = new JPanel(); gbc = new GridBagConstraints(); gbc.gridx = 1; gbc.gridy = 3; gbc.gridwidth = 2; gbc.fill = GridBagConstraints.VERTICAL; panell.add(spacer2, gbc); final JPanel spacer3 = new JPanel(); gbc = new GridBagConstraints(); gbc.gridx = 2; gbc.gridy = 5; gbc.fill = GridBagConstraints.VERTICAL; gbc.insets = new Insets(0, 250, 0, 0); panell.add(spacer3, gbc); final JPanel spacer4 = new JPanel(); gbc = new GridBagConstraints(); gbc.gridx = 1; gbc.gridy = 5; gbc.fill = GridBagConstraints.VERTICAL; panell.add(spacer4, gbc); final JPanel spacer5 = new JPanel(); gbc = new GridBagConstraints(); gbc.gridx = 2; gbc.gridy = 1; gbc.fill = GridBagConstraints.VERTICAL; gbc.insets = new Insets(25, 0, 0, 0); panell.add(spacer5, gbc); final JLabel label1 = new JLabel(); label1.setText("Label"); gbc = new GridBagConstraints(); gbc.gridx = 2; gbc.gridy = 0; panell.add(label1, gbc); final JPanel spacer6 = new JPanel(); gbc = new GridBagConstraints(); gbc.gridx = 0; gbc.gridy = 6; gbc.fill = GridBagConstraints.VERTICAL; gbc.insets = new Insets(30, 0, 0, 0); panell.add(spacer6, gbc); final JPanel spacer7 = new JPanel(); gbc = new GridBagConstraints(); gbc.gridx = 0; gbc.gridy = 2; gbc.fill = GridBagConstraints.VERTICAL; gbc.insets = new Insets(30, 0, 0, 0); panell.add(spacer7, gbc); } /** * @noinspection ALL */ public JComponent $$$getRootComponent$$$() { return panell; } } 

Thanks in advance! I hope some of you can figure out a way I can fix my code :(

Regards

Answer 1

Well what I'll start out saying is that you are correct: never use a GUI Builder. I don't even mean when you're trying to learn, I mean never use it. It's mainly there for prototyping a concept and not meant for you to use it for learning or production code. Below is a cleaned up more precise example for you, but in your particular example, you need to add your

new JFrame().setVisible(true);

inside of your onNewUserClicked function. Also, note that when you do that, you're creating an empty frame, that will be the absolute minimum amount of size that it takes for your OS to create it because there's nothing in it, you never packed the frame, and never manually and explicitly set the size, so check around your top left area of your monitor - it's there.

Here is probably closer to what you want in terms of cleanliness.

public class Foo {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                final JFrame jf = new JFrame();
                JPanel jp = new JPanel();
                JButton jb = new JButton("New Frame");
                jb.addActionListener(new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        jf.setVisible(false);
                        new JFrame().setVisible(true);
                    }
                });
                jp.setLayout(new FlowLayout());
                jp.add(jb);
                jf.setContentPane(jp);
                jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                jf.setVisible(true);
                jf.pack();
            }
        }
    }
}

The reason why I say cleaner at all, is because of the control of a LayoutManager. GUI builders like the one you use always tend to use GridBagLayout because it's easier for it to dynamically (from your user input) place things precisely. But the code it generates is unmanageable. And things get worse when you consider that if you expand or contract your GUI, that the GridBagLayout is not flexible with this so now your Components are stuck exactly where you placed them when dragging them from the GUI Builder. Proper use of the correct LayoutManager will give you a flexible and manageable GUI. Check out this Oracle guide for more info and help: https://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html

Answer 2

That is because you are disposing the parent frame before showing the new one.

In this scenario your parent frame, from which you are calling

new JavaFrame2().SetVisibility(true);

contains the handle to the new JavaFrame. By disposing the parent frame you technically delete the parent -> you cant do something with it any more.

Try hiding the startscreen by calling .SetVisibility(false) instead of this.dispose(); .