Question

Can someone work out why my JScrollPane is not working. Perhaps something I may have missed. I realize this might be silly without any more context than what I’ve shown but please ask and I shall be happy to provide more.

public ApplicationFrame(String title, int x, int y, int width, int height) {
        // Constructor for the ApplicationFrame, no implicit Construc.
        setTitle(title);
        setResizable(true);
        setBounds(x, y, width, height);
                    setLayout(new BorderLayout());
        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        setIconImage(new ImageIcon(getClass().getResource("resources/topLeft.png")).getImage());
        topMostMenuBar = new TopMenuBar(this);
        setJMenuBar(topMostMenuBar.getMyJMenuBar());
        paneEdge = BorderFactory.createLineBorder(Color.gray);
        blackline = BorderFactory.createLineBorder(Color.black);
        this.frameContent = new ApplicationPanel() {
            //@Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.drawImage(TI, 0, 0, null);
            }
        };
        mainImageScrollPane = new JScrollPane(frameContent);
        statusPanel = new ApplicationPanel(new Color(0xfff0f0f0));
        leftPanel = new ApplicationPanel(new Color(0xfff0f0f0));
        testPanel = new ColorPanel(new Color(0xfff0f0f0));
        testPanel.setPreferredSize(new Dimension(50,300));
        add(mainImageScrollPane, BorderLayout.CENTER );
        add(statusPanel, BorderLayout.SOUTH);
        add(leftPanel, BorderLayout.WEST);
        Container visibleArea = getContentPane();
        visibleArea.add(frameContent);
        setVisible(true);
        do {
            loadImageIn();
        } while (!initLoadSuccess);
        initButtons();
        leftPanel.add(testPanel, BorderLayout.SOUTH);
    } // end Constructor **

This is a big piece of code so I’m not sure how to make an SSCCE out of it. What youre looking at is the constructor to my subclass of a JFrame, which holds 3 panels. The ApplicationPanel is at this point just a JPanel. The loadImageIn() method opens a filechooser and then loads the chosen image which is painted onto frameContent. The image displays fine, everything works, except when I resize the window, there are no scrollbars.

Answer 1

You have this line, which adds the ApplicationPanel to the visibleArea…

visibleArea.add(frameContent);

Maybe you actually mean this, which adds the JScrollPane to the visibleArea (and the JScrollPane already contains the ApplicationPanel)…

visibleArea.add(mainImageScrollPane);

When you call new JScrollPane(frameContent), it doesn’t do anything to the panel inside it, it just adds a wrapper around the outside. So, if you want the ability to scroll, you need to refer to the JScrollPane wrapper, rather than the panel itself.