List Models

• It is surprisingly difficult to add an item to a JList that already exists.  You have to get into the guts of the JList, into the Model - View - Controller design.
• The JList only displays data.  It does not actually store data.  It knows how to get the data, though.
• It is the job of the ListModel to actually store the data.
• If you pass an Array or Vector of data to a JList, it creates a model for you.
• But, if you need to perform more complex tasks, such as adding or removing data dynamically, you'll need to develop your own model.
• The ListModel interface has four methods that the JList uses to get data:
• public int getSize() returns the number of elements in the list.
• public Object getElementAt(int i) gets the ith element from the model.
• public void addListDataListener(ListDataListener l) adds a ListDataListener to the model.
• public void removeListDataListener(ListDataListener l) removes the ListDataListener from the model.
• The JList uses these methods to count and retrieve the elements in the model.  It can also add itself as a listener so that it can repaint the list when items are added or removed.
• The use of the ListModel allows you to store the items any way you wish.  You can store them in a more complex object than a Vector, perhaps add some logic to the get methods as well.  This gives you the liberty of complete flexibility.

Created by:  Brandan Jones December 17, 2001