Question

Looking round Stack exchange I can’t find a good answer to this. Most of the code in similar questions I’ve seen look massive and bloated where an error could easily creep in; I can’t see if I’m making the same mistake or not.

I only have two classes (and an interface), my probelm being is that my JTable is blank:

Here is my code:

Launch the program

public class Launcher {


    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                IViewManager.Util.getInstance();
            }
        });
    }
}

Start the ViewManager frame

public class ViewManager implements IViewManager {

    JFrame frame = null;
    JTabbedPane myListTabs = null;
    ComicsListPane myComicsListPane = null;

    public ViewManager(){

    //Create and set up the window.
    frame = new JFrame("My List Agregator");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Add the Tabbed pane for lists.
    myListTabs = new JTabbedPane();
    myComicsListPane = new ComicsListPane();
    myListTabs.add(myComicsListPane);
    myListTabs.setTitleAt(myListTabs.getTabCount()-1, "title");
    frame.getContentPane().add(myListTabs);

    //Display the window.
    frame.pack();
    frame.setVisible(true);
    }
}

The Comics List Pane

public class ComicsListPane extends JPanel {
    /**
     * 
     */
    private static final long serialVersionUID = -5207104867199042105L;
    JTable myComicsTable = null;

        public ComicsListPane() {
                //Create the column names and data
            String[] columnNames = {"Comic Title",
                    "Volume",
                    "Edition",
            "Purchased"};

            Object[][] data = {
                    {"The Amazing Spider-man", new Integer(3),
                        new Integer(679), new Boolean(false)},
                        {"The Amazing Spider-man", new Integer(3),
                            new Integer(680), new Boolean(false)}
            };
            //Create the table
            myComicsTable = new JTable(data, columnNames);
            myComicsTable.setPreferredScrollableViewportSize(new Dimension(750, 110));
            myComicsTable.setFillsViewportHeight(true);
            myComicsTable.setFillsViewportHeight(true);

            JScrollPane scrollPane = new JScrollPane(myComicsTable);        
            scrollPane.add(myComicsTable);
            scrollPane.setPreferredSize(new Dimension(450, 110));
            this.add(scrollPane, BorderLayout.CENTER);
        }
    }

I can’t see where I’ve gone wrong, mostly I’ve copied form the Java Doc Tutorials.

Could someone help point out the error, to a java novice?

Answer 1

It looks like your problem is when you create the JScrollPane.

JScrollPane scrollPane = new JScrollPane(myComicsTable);        
scrollPane.add(myComicsTable);

The second line here is not needed – you’ve already constructed the JScrollPane with the JTable, there’s no need to then add it to the JScrollPane. Indeed – this is using the add() method from Container. Exactly why it’s causing the behaviour you are seeing is not clear to me without looking at the javadocs/source in more detail.

As an aside, when you’re working with GUIs (and indeed, generally) it’s best to narrow your code down to the smallest chunks. i.e. a method to create the JTable – can that be displayed? Then, a method to wrap it in a JScrollPane – does display as you would wish? etc. etc.