Java™ Application Development on Linux - Dator

366Chapter 16Getting in the Swing of Things: Designing a GUI for BudgetProThis call tells our table (list) that we want to allow the user to select onlya single row or column at a time. Valid options are:ListSelectionModel.SINGLE_SELECTIONListSelectionModel.SINGLE_INTERVAL_SELECTIONListSelectionModel.MULTIPLE_INTERVAL_SELECTIONThe latter two allow the user to select more than one row at a time; multipleintervals mean that the selected rows can be discontinuous. (Think“Shift+click” versus “Control+click” as the user action that selects these.)So what will our program do, once the user has made a selection? The selectedrow is a subaccount of the current account and we will allow the user todisplay that account and its subaccount, if any. Think of it as “changingdirectory” into that account, to look at or change its status.For a table to take an action when a selection is made you need anotherlistener called a selection listener. We wrote:196 list.getSelectionModel().addListSelectionListener(197 new ListSelectionListener()198 {199 public void200 valueChanged(ListSelectionEvent e)201 {202 ListSelectionModel lsm =(ListSelectionModel)e.getSource();203 if (lsm.isSelectionEmpty()) {204 view.setEnabled(false);205 } else {206 view.setEnabled(true);207 }208 } // valueChanged209 }210 );Similar to how a table has a table model behind it, it also has a selectionmodel behind it. We don’t need to reimplement an entire selection model; wejust retrieve the default one from our table (list.getSelectionModel())and add a listener to it so that it will notify us when something has changed.The javax.swing.event.ListSelectionListener is an interface withonly one method, so it’s easy to extend and override it in place, as we do, beginningat line 197. When called, it will be handed an event (e) and we take thesource of that event and coerce it to a ListSelectionModel. That’s safe to