Question

How can I get the scroller around my JList component in the code given below? It doesn’t seem to work properly 🙁

 public class JButtonO extends JFrame{

String[] values = {"henry", "Michael","Uche","John","Ullan","Nelly",
                              "Ime","Lekan","Austine","jussi","Ossi","Imam","Empo","Austine","Becky",
                             "Scholar","Ruth", "Anny"};

 public JButtonO()
{
   super("the button");
   this.setSize(400,200);
   JPanel panel =  new JPanel();
   JLabel label = new JLabel("Output Items:");
   label.setAlignmentX(1);
   label.setAlignmentY(1);
   JList conList = new JList(values);
   conList.setVisibleRowCount(3);
   JScrollPane scroller = new JScrollPane(conList);
   panel.add(label);
   panel.add(scroller);
   panel.add(conList);

   this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   this.add(panel);
   this.setVisible(true);


}

Answer 1

Look, I may not answering what you need, because I don´t remember to much of swing layout. I don´t work with it a long time ago…

But removing setting a layout (I remember) on your JPanel it works with this code:

public JButtonO() {
    super("the button");
    this.setSize(400, 200);

    // Create a panel with a borderlayout
    JPanel jpanel = new JPanel(new BorderLayout());

    JLabel label = new JLabel("Output Items:");
    label.setAlignmentX(1);
    label.setAlignmentY(1);
    // Add Label to top of layout
    jpanel.add(label, BorderLayout.NORTH);

    JList conList = new JList(values);
    conList.setVisibleRowCount(3);
    JScrollPane scroller = new JScrollPane(conList);
    //AddScroll to center
    jpanel.add(scroller);

    //Add Panel to JFrame
    this.add(jpanel);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setVisible(true);

  }

I think the problems is the default layoutmaneger of JPanel. Because of how it works your scroll was not “srink” enough to create scrolls…

Hope it helps, even without too much explanation…

ACTUALLY: After I post the answer I saw your mistake. Now I can explain what is wrong. You already added your JList inside your JScrollPane here:

JScrollPane scroller = new JScrollPane(conList);

But after that you put it inside the JPanel:

panel.add(conList);

this changes where yout JList will be displayed, and let the JScroll empty again. Without components it will be displayed with size 0x0 and will not be draw (even being there).

Now I think I helped =D