Java Reference
In-Depth Information
fileMenu.setMnemonic('F'); // Create shortcut
elementMenu.setMnemonic('E'); // Create shortcut
The
setMnemonic()
method is inherited from the
AbstractButton
class, so all subclasses of this
class inherit this method. The argument is a character in the
String
that is the label for the item that is
to be the shortcut character - under Windows the
File
menu would then pop up if you key
Alt+F
. The
effect of
setMnemonic()
is to implement the shortcut and underline the shortcut character letter in
the menu label.
An
accelerator
is a key combination that you can enter to select an item from a menu. Under Windows, the
Ctrl
key is frequently used in combination with a letter as an accelerator for a menu item, so
Ctrl+L
might be
the combination for the
Line
item in the
Elements
menu. For menu items you call the
setAccelerator()
method to define an accelerator. For example, for the
Line
menu item you could write:
lineItem.setAccelerator(KeyStroke.getKeyStroke('L', Event.CTRL
_
MASK ));
The
KeyStroke
class defines a keystroke combination. The static method,
getKeyStroke()
returns
the
KeyStroke
object corresponding to the arguments. The first argument is the character and the
second argument specifies the modifier key. The
Event
class (in
java.awt
) defines
Event.SHIFT
_
MASK
,
Event.ALT
_
MASK
, and what we used here,
Event.CTRL
_
MASK
. If you want to
combine the
Alt
and
Ctrl
keys for instance, you can add them -
Event.ALT
_
MASK +
Event.CTRL
_
MASK.
Let's see how this works in practice.
Try It Out - Adding Menu Shortcuts
We can add some shortcuts to Sketcher by amending the statements that add the items to the
File
menu
in the
SketchFrame
class constructor:
// Frame for the Sketcher application
import javax.swing.*;
import java.awt.Event;
public class SketchFrame extends JFrame {
// Constructor
public SketchFrame(String title) {
setTitle(title); // Call the base constructor
setDefaultCloseOperation(EXIT
_
ON
_
CLOSE);
setJMenuBar(menuBar); // Add the menu bar to the window
JMenu fileMenu = new JMenu("File"); // Create File menu
JMenu elementMenu = new JMenu("Elements"); // Create Elements menu
fileMenu.setMnemonic('F'); // Create shortcut
elementMenu.setMnemonic('E'); // Create shortcut
// Construct the file pull down menu as before...
// Add File menu accelerators
newItem.setAccelerator(KeyStroke.getKeyStroke('N',Event.CTRL
_
MASK ));
