Java ScrollPane overlapping contents

Question

I'm having what I am sure is very much a beginners problem with my JScrollPanes. The problem is that the vertical scrollbar overlaps the components within the enclosed panel (on the right hand side). It becomes a bit of a pain when the scrollbar overlaps the drop-down bit of JComboBoxes.

I have boiled the problem down to this little snippet - I hope it illustrates the issue.

public class ScrollTest extends JFrame
{
    public ScrollTest()
    {
        super("Overlap issues!");
        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(100,0));

        for(int b=0;b<100;++b)
        {
            panel.add(new JButton("Small overlap here ->"));
        }

        JScrollPane scrollpane = new JScrollPane(panel);
        add(scrollpane);
        pack();
        setVisible(true);
    }

    public static void main(String[] args) 
    {
        new ScrollTest();
    }
}

I had a look first but couldn't see if anyone else had already addressed this problem. Sorry if it's a duplicate and many thanks for any help anyone can offer a java-newb like me!

Answer 1

The problem is that the default for a JScrollPane is to layout the components with a default of JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED which in turn adds the scrollbar without laying out the components again.

In your example you know you will need a scrollbar so change it to always display the scrollbar

public class ScrollTest extends JFrame
{
    public ScrollTest()
    {
        super("Overlap issues!");
        JPanel panel = new JPanel();
        //Insets insets = panel.getInsets();
        //insets.set(5, 5, 5, 25);
        //insets.set(top, left, bottom, right);
        panel.setLayout(new GridLayout(100,0));

        for(int b=0;b<100;++b)
        {
            panel.add(new JButton("Small overlap here ->"));
        }

        JScrollPane scrollpane = new JScrollPane(panel);
        scrollpane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
        add(scrollpane);
        pack();
        setVisible(true);
    }

    public static void main(String[] args) 
    {
        new ScrollTest();
    }
}