Sorry for the title, probably too generic.
I already read How to Write an Action Listener tutorial by Java and I already read this question, but I still have some doubts: I was wondering which solution is the best when I have to perform the same action multiple time.
I'd want to reuse the same ActionListener, but I am not sure on how to achieve this in the best way (speaking in term of: code readability, code mantainability, performance and code style).
First the "standard" code (which I would use if I'm not going to reuse the action listener):
btnMenu.addActionListener(
new ActionListener() {
public void actionPerformed(ActionEvent e) {
Navigator.showMenu();
}
}
);
This way I can't reuse anything obv, since it's an anonymous inner class...
Now, I can think of the following solutions:
- Store a reference of an Anonymous Inner Class in a field (that will most likely be
static final); - Write a new class that implements
ActionListenerinterface.
Example code for solution 1:
public static final MENU_ACTION_LISTENER = new ActionListener() {
public void actionPerformed(ActionEvent e) {
Navigator.showMenu();
}
};
btnMenu.addActionListener(MENU_ACTION_LISTENER);
Example code for solution 2:
// package-private, only GUI-package classes should be able to use it.
// most likely I won't ever need to subclass it, so why not making it final?
final class MenuActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
Navigator.showMenu();
}
}
// now, wherever I need to use it:
btnMenu.addActionListener(new MenuActionListener());
I have some doubts about both solutions:
Where to store references to Anonymous Action Listeners? I could have a sort of utility class (e.g.
ActionListenersUtil) where store all action listeners I want to reuse instatic finalfields, but I don't like it... it seems to me poor design.It makes more sense, probably best follows the Command Pattern... I initially had some doubt about the packages... I'd like to have all listeners in a separate package (e.g.
com.myapp.guifor gui elements andcom.myapp.gui.listenersfor listeners. But when I wrote down this I realized that I have no choice: the only place where it make sense is in the same package (because they must be package-private), even if for the sake of order I would have like to put them all in a separate package. I still have some doubt though, because most action listeners may be reusable even in case GUI changes; it still would be a good idea to have it in the same package?
Another question: what's the difference between calling btnMenu.addActionListener(MENU_ACTION_LISTENER); and btnMenu.addActionListener(new MenuActionListener()); (speaking in term of JVM, class loading, class compiling, memory occupied by each class, garbage collection and so on)?
Please help, I'm so confused right now! :(