Java - Updating JList after changing an object

Question

I have a JList which uses a DefaultListModel.

I then add values to the model which then appear in the JList. I have created a MouseListener which (when double clicked) allows the user to edit the current user number of that person they have selected.

I have checked that the actual object of that record is being changed, and it is. The only issue I'm having is getting the actual Jlist to update to show the new values of that object.

Snippets of the current code I have are:

Creating the JList and DefaultTableModel:

m = new DefaultListModel();
m.addListDataListener(this);
jl = new JList(m);
jl.addMouseListener(this);

Updating the object:

String sEditedNumber = JOptionPane.showInputDialog(this, "Edit number for " + name, number);
if (sEditedNumber != null) {
    directory.update (name, sEditedNumber);
}

And (when jl is the JList and m is the DefaultTableModel):

public void contentsChanged(ListDataEvent arg0) {
        jl.setModel(m);
    }

Answer 1

You need to call fireContentsChanged() on the ListModel.

Answer 2

Instead of setModel(), update your existing model using one of the DefaultListModel methods such as setElementAt(), which will fireContentsChanged() for you.

Answer 3

You need to call DefaultListModel.fireContentsChanged(). But since this method is protected (I really wonder why), you can't do that directly. Instead, make a small subclass:

class MinoListModel<T> extends DefaultListModel<T>
{
    public void update(int index)
    {
        fireContentsChanged(this, index, index);
    }
}

Use it as your list model:

m = new MinoListModel<>();
jl = new JList(m);

After updating a user number, update the corresponding entry: m.update(theIndex);

Alternatively, if you don't want a subclass, you can just replace the JList element after the user number changed: m.setElementAt(theSameElement, theIndex);. Though this is somewhat cumbersome and having a subclass seems the cleaner approach.