Java™ Application Development on Linux - Dator

368Chapter 16Getting in the Swing of Things: Designing a GUI for BudgetProAs long as this returned Account is not null (line 66), we can make it thecurrent account (line 67). At that point the display needs to be updated, so we:1) call our own setStatus() method, to update the upper portion of ourGUI, and 2) tell the table that its data has changed (line 71).16.7.2.11 Ready, aim, fire!A word about the fire...() methods. They are not part of the TableModelinterface definition. Rather, they are part of the AbstractTableModel class.When a Java class is declared abstract it means that some methods need to beimplemented by those classes that use (extend) this class. An abstract class canstill have lots of intact, completely implemented methods, and that is the casewith AbstractTableModel.The TableModel interface defines methods for adding and removing listeners.Any implementation of the TableModel interface needs to supportthese, and to notify any listeners when a change occurs. Such listeners will receivea call to their tableChanged() method when such a change occurs. Butit doesn’t tell us how such notification is triggered. Moreover, the change event,when received by the listener, needs to define the extent of the change—just asingle cell? a whole row? a column? all columns? and so on.The AbstractTableModel provides some methods for us to call when achange in the data has occurred, methods that will then notify all the registeredlisteners (Table 16.1). Moreover, it has different methods depending on theextent of the change, so that the TableModelEvent, sent to allTableModelListeners, can be constructed with the appropriate definition ofwhat has changed.We used (line 71) the fireTableDataChanged() since the content ofthe table will change with a change of accounts, but the structure remains thesame. It is also a handy all-purpose method for you to use if you’d rather notadd the complexity of determining which rows have changed to your code.Finally, remember that anyone who uses (extends) AbstractTableModel,including the DefaultTableModel class, gets these methods for their use.There are several other interactions that are supported by JTables, onesthat don’t require you to do anything to provide them to your application’send user. When running the BudgetPro GUI, did you try to drag the columnheadings? You can also rearrange and resize columns. This is the default behaviorfor JTables. You can turn it off, however, if you want your columns tobe fixed: