Java JPanel inside JScrollPane?

Question

I have a JFrame, in this JFrame I have a JPanel that I draw on, this Panel can be any size and so I placed it into a JScrollpane to let me scroll when the panel is larger th

Answer 1

As far as I remember there are 2 options:

• define the preferredSize of _ImageCanvas
• create a subclass of JPanel and implement Scrollable: http://docs.oracle.com/javase/7/docs/api/javax/swing/Scrollable.html

For more details, see the Javadoc: http://docs.oracle.com/javase/7/docs/api/javax/swing/JScrollPane.html

Answer 2

// suggest a size of 'canvas'
_ImageCanvas.setPreferredSize(new Dimension(100,100));

// Scroll pane smaller then the size of the canvas so we should get scroll bars right?
_ScrollPane.setPreferredSize(new Dimension(50,50)); 

// ..later 
_Frame.pack();

Answer 3

Check out the Scrollable interface, this may help with the sizing issues.

These two method maybe helpful:

boolean getScrollableTracksViewportWidth();

boolean getScrollableTracksViewportHeight();

Answer 4

• Set preferred size on the canvas.
• Increase dimensions 100,100 is too small atleast on my computer.
• You may want to use new GridLayout(1,1); for you JFrame if you want the scrollpane to expand when you expand the frame.

Answer 5

setPreferredSize() is the trick, setMinimumSize() and even setSize() on the component will be ignored by JScrollPane. Here's a working example using a red border.

import java.awt.*;

import javax.swing.*;

public class Scroller extends JFrame {

    public Scroller() throws HeadlessException {
        final JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createLineBorder(Color.red));
        panel.setPreferredSize(new Dimension(800, 600));

        final JScrollPane scroll = new JScrollPane(panel);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());
        add(scroll, BorderLayout.CENTER);
        setSize(300, 300);
        setVisible(true);
    }

    public static void main(final String[] args) throws Exception {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Scroller().setVisible(true);
            }
        });
    }
}