Java Reference
In-Depth Information
The
AbstractAction
class definition already provides the mechanism for storing action properties. For
the last two constructors, the argument values are stored using the standard keys in the
Action
interface that
I described earlier. For the moment, you use the constructor with just a name argument and leave icons until
a little later.
Actions for File Menu Items
You can define the
FileAction
inner class as follows:
// Inner class defining Action objects for File menu items
class FileAction extends AbstractAction {
// Create action with a name
FileAction(String name) {
super(name);
}
// Create action with a name and accelerator
FileAction(String name, char ch, int modifiers) {
super(name);
putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke(ch, modifiers));
// Now find the character to underline
int index = name.toUpperCase().indexOf(ch);
if(index != -1) {
putValue(DISPLAYED_MNEMONIC_INDEX_KEY, index);
}
}
// Event handler
public void actionPerformed(ActionEvent e) {
// You will add action code here eventually...
}
}
Directory "Sketcher 6 using Action objects"
You have two constructors. The first just stores the name for the action as the
NAME
property by calling
the base class constructor. The second stores the name by calling the first constructor and then creates
and stores the accelerator keystroke in the
Action
object as the value for the
ACCELERATOR_KEY
property.
You create the
KeyStroke
object from the
ch
and
modifiers
arguments. The character,
ch
, must always
be an uppercase letter because lowercase letters are used to identify non-alphabetic keys in a keystroke.
You find the index of the character in the name that corresponds to
ch
and use that as the value for the
DISPLAYED_MNEMONIC_INDEX_KEY
property. This causes the character at that index position in the name to
be underlined.
Because the class is an action listener, you have implemented the
actionPerformed()
method in it. You
don't yet know what you are going to do with the File menu item actions, so you can leave it open for
now and let the
actionPerformed()
method do nothing. Alternatively you could add a statement to output
