Re: JScrollPane doesn't resize properly

Andrew Thompson wrote:


Below is an example of an SSCCE. It has a JPanel in a JScrollPane in a
JFrame. clicking the panel randomly resizes it, causing scrollbars to
appear as needed.

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import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;

public class PanelScroller extends JPanel implements MouseListener {

    JPanel drawing;

    JLabel sizeLabel = new JLabel(" Click Me! ");

    Random r = new Random();

    PanelScroller() {
        drawing = new JPanel();
        drawing.add(sizeLabel);
        drawing.setBackground(Color.BLUE);
        drawing.addMouseListener(this);
        setPanelSize(300, 200);

        JScrollPane scroller = new JScrollPane(drawing);
        add(scroller);
    }

    void setPanelSize(int w, int h) {
        sizeLabel.setText(w + " x " + h);
        Dimension d = new Dimension(w, h);
        drawing.setPreferredSize(d);
        drawing.setMaximumSize(d);
        drawing.setMinimumSize(d);
        drawing.setSize(d);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JFrame f = new JFrame("App Title");
                f.add(new PanelScroller());
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.pack();
                f.setVisible(true);
            }
        });
    }

    public void mouseClicked(MouseEvent arg0) {
        int width = 250 + r.nextInt(100);
        int height = 150 + r.nextInt(75);
        setPanelSize(width, height);
    }

    public void mousePressed(MouseEvent arg0) {}
    public void mouseReleased(MouseEvent arg0) {}
    public void mouseEntered(MouseEvent arg0) {}
    public void mouseExited(MouseEvent arg0) {}
}
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Making it work sensibly when the JFrame is resized is left as an exercise
for the reader :-)