Question

I have been working on an app, where you set up a list of categories with items in it, which will then be made into a text file. But the GUI I’ve made for it doesn’t work entirely. I think the error is situated in the JMenuItem called Cat (or “add category”) or in the way I display the Categories (Update() method). It is supposed to ask for a name, make a Category named after that and display it in a JScrollPane, but nothing comes up. Here is the code:

public class GUIBuilder {
    public JFrame frame;
    public JPanel LeftPanel;
    public JPanel RightPanel;
    public JScrollPane scroll;
    public JMenuBar bar;
    public JMenu File;
    public JMenu Add;
    Inventory inv;

    public void go() {
        frame = new JFrame();

        scroll = new JScrollPane();

        bar = new JMenuBar();
        File = new JMenu("File");
        Add = new JMenu("Add...");
        bar.add(File);
        bar.add(Add);

        JMenuItem Save = new JMenuItem(new AbstractAction("Save") {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent arg0) {

            }
        });
        JMenuItem Load = new JMenuItem(new AbstractAction("Load") {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent arg0) {

            }
        });
        JMenuItem Generate = new JMenuItem(new AbstractAction("Generate Text File") {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent arg0) {

            }
        });
        File.add(Save);
        File.add(Load);
        File.add(Generate);

        JMenuItem Cat = new JMenuItem(new AbstractAction("Add Category") {
            private static final long serialVersionUID = 1L;
            JFrame Cat;

            public void actionPerformed(ActionEvent arg0) {
                Cat = new JFrame("Add Category");
                final JTextField name = new JTextField(15);
                JButton Submit = new JButton(new AbstractAction("Submit") {
                    private static final long serialVersionUID = 1L;

                    public void actionPerformed(ActionEvent arg0) {
                        String n = name .getText();
                        if (n != null) {
                            inv.addCategory(new Category(n));
                            pullThePlug();
                            GUIBuilder.this.Update();
                        }
                    }
                });
                Cat.setLayout(new BorderLayout());
                Cat.add(name, BorderLayout.CENTER);
                Cat.add(Submit, BorderLayout.SOUTH);
                Cat.setSize(250, 150);
                Cat.setVisible(true);
            }
            public void pullThePlug() {
                WindowEvent wev = new WindowEvent(Cat, WindowEvent.WINDOW_CLOSING);
                Toolkit.getDefaultToolkit().getSystemEventQueue().postEvent(wev);
            }
        });
        JMenuItem item = new JMenuItem(new AbstractAction("Add Item") {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent arg0) {

            }
        });
        Add.add(Cat);
        Add.add(item);

        frame.setJMenuBar(bar);
        frame.setSize(500, 800);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.add(scroll);

        inv = new Inventory();
    }

    public void Update() {
        for (int i = 0; i < inv.categories.size(); i++) {
            Category cat = inv.categories.get(i);
            JPanel p = new JPanel();
            JTextPane name = new JTextPane();
            name.setText(cat.getName());
            scroll.add(p);
        }
    }
}

Thanks in advance 😉

Answer 1

You need to add your JTextPane name to your JPanel p.

(It also seems to me that you’re missing a main method that will construct a GUIBuilder – but maybe that’s in another file that you haven’t shown in your question?)

---

Also, if you create an empty JScrollPane, you need to add components via scrollpane.getViewport().add(yourcomponent);.

You also need some layout management. The easiest way (and probably what you intended to do anyways) is:

    public void Update() {
        JPanel p = new JPanel();
        for (int i = 0; i < inv.categories.size(); i++) {
            Category cat = inv.categories.get(i);
            JTextPane name = new JTextPane();
            p.add(name);        
            name.setText(cat.getName());                
        }
        scroll.getViewport().add(p);       
    }