Java Reference
In-Depth Information
Command (Chapter 24)
SOLUTION 24.1
Java Swing applications commonly apply the M
EDIATOR
pattern, registering a single object to
receive all GUI events. This object mediates the interaction of the components and translates
user input into commands for business domain objects.
SOLUTION 24.2
Your code should look something like:
protected JMenu fileMenu()
{
if (fileMenu == null)
{
fileMenu = new JMenu("File");
Font f = SwingFacade.getStandardFont();
fileMenu.setFont(f);
JMenuItem save = new JMenuItem("Save");
save.setFont(f);
fileMenu.add(save);
save.addActionListener
(
new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
save();
}
}
);
JMenuItem load = new JMenuItem("Load");
load.setFont(f);
fileMenu.add(load);
load.addActionListener
(
new ActionListener()
{
public void actionPerformed(ActionEvent e) {
load();
}
}
);
}
return fileMenu;
}
Although the
actionPerformed()
method requires an
ActionEvent
argu-ment, you can
safely ignore it. The
fileMenu()
code registers a single in-stance of an anonymous class
with the Save menu item and a single instance of another anonymous class with the Load
menu item. When these methods are called, there is no doubt about the source of the event.
