Question

I have JScrollPane which contains only one instance of JTree. How can I set margin around JTree inside of JScrollPane?

I have such a code

tree.setPreferredSize(new Dimension(200, 200));
    JScrollPane scrollerTree = new JScrollPane(tree, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
    scrollerTree.setPreferredSize(new Dimension(200, 199));
    scrollerTree.getVerticalScrollBar().setUnitIncrement(16);

I want to achieve, that margin would be scrollable with scrollpane content.

Answer 1

Update: From your updated question I reckon that you are actually after JComponent.setBorder, example screenshot:

Code:

public static void main(String[] args) {

    JTree tree = new JTree();
    tree.setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));

    JFrame frame = new JFrame("Test");
    frame.add(new JScrollPane(tree));
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setVisible(true);
}

---

Original answer, if you want a border around the view port, use JScrollPane.setViewportBorder:

Code:

public static void main(String[] args) {

    JScrollPane scroll = new JScrollPane(new JTree());
    scroll.setViewportBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

    JFrame frame = new JFrame("Test");
    frame.add(scroll);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setVisible(true);
}