Java (Swing): JScrollPane.setBounds() does not apply?

Question

I'm trying to create a simple JList with a scrollbar, and therefore i need to have the JList within a JScrollPane. So far, so good. However, for some reason i can't resize/position the JScrollPane!? It sounds logic that everything inside it should stretch to 100%, so if i set the JScrollPane to be 300px wide, the elements inside will be as well. Is that correct?

While you're at it, please critisize and give me hints if i should change something or optimize it.

Anyhow, here's the code:

package train;
import java.awt.*;
import javax.swing.*;

public class GUI {

    private DefaultListModel loggerContent = new DefaultListModel();
    private JList logger = new JList(loggerContent);

    GUI() {
        JFrame mainFrame = new JFrame("title");


        this.addToLog("testing testing");
        this.addToLog("another test");


        // Create all elements
        logger = new JList(loggerContent);

        JScrollPane logWrapper = new JScrollPane(logger);
        logWrapper.setBounds(10, 10, 20, 50);


        // Add all elements
        mainFrame.add(logWrapper);


        // Show everything
        mainFrame.setSize(new Dimension(600, 500));
        mainFrame.setVisible(true);
    }

    public void addToLog(String inputString) {
        int size = logger.getModel().getSize();
        loggerContent.add(size, inputString);
    }

}

Thanks in advance, qwerty

EDIT: Here's a screenshot of it running: http://i.stack.imgur.com/sLGgQ.png

Answer 1

The setVisibleRowCount() method of JList is particularly convenient for this, as suggested in the relevant tutorial . ListDemo is a good example.

Addendum:

please critisize and give me hints…

Well, since you ask: Don't invoke public methods in the constructor; make them private or invoke them after the constructor finishes. There's no need to find the last index for add() , when addElement() is available. Also, be sure to construct your GUI on the event dispatch thread .

import java.awt.*;
import javax.swing.*;

/** @see http://stackoverflow.com/questions/5422160 */
public class ListPanel extends JPanel {

    private DefaultListModel model = new DefaultListModel();
    private JList list = new JList(model);

    ListPanel() {
        list.setVisibleRowCount(5);
    }

    public void append(String inputString) {
        model.addElement(inputString);
    }

    private void init() {
        for (int i = 0; i < 10; i++) {
            this.append("String " + String.valueOf(i));
        }
        JFrame mainFrame = new JFrame("GUI");
        mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JScrollPane jsp = new JScrollPane(list);
        mainFrame.add(jsp);
        mainFrame.pack();
        mainFrame.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new ListPanel().init();
            }
        });
    }
}

Answer 2

Try to put your JScrollPane inside a JPanel and add the panel to the frame.

JPanel panel = new JPanel();
panel.add (logWrapper);
mainFrame.add(panel);

Then set the bounds of the panel instead of the JScrollpane

panel.setBounds(10, 10, 20, 50);

The probles is that Swing uses layout managers to control child bounds property. Adding a JScrollpane directly to the main frame, doesn't allow you to choose right bounds properly.

Answer 3

The bounds & size of a component are generally ignored over that of it's preferred size and the constraints of the layout being used by the container.

To solve this problem, learn how to use layouts & apply them appropriately.