Using InputMap and ActionMap

Question

Referring to an earlier post "Listening to Keystrokes", I already know how to
trap keystrokes in a JPanel. I use this line of code:
this.registerKeyboardAction(this,
      "Exit Task", KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE, 0),
      JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);[/cpde]
However, the documentation for registerKeyboardAction() states:
This method is now obsolete, please use a combination of getActionMap() and
getInputMap() for similiar behavior. For example, to bind the KeyStroke
aKeyStroke to the Action anAction now use:
   component.getInputMap().put(aKeyStroke, aCommand);
component.getActionMap().put(aCommmand, anAction);
Therefore, I attempt to use the getInputMap() and getActionMap() method. Since the documentation for registerKeyboardAction is:public void registerKeyboardAction(ActionListener anAction,
                                   String aCommand,
                                   KeyStroke aKeyStroke,
                                   int aCondition)I thought inside the JPanel, I only have to add these lines:
this.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE, 0), "Exit Task");
this.getActionMap().put("Exit Task", this);Unfortunately, the second line will give compilation errors. Note that the JPanel already implements ActionListener. So I check the documentation for ActionMap and realise that the put() method has two parameters, Object key and Action anAction. It seems that I have to this (a JPanel class) to Action. I thought casting should work since ActionListener is a superinterface to Action, but when I run the program, it will throw a ClassCastException.
Therefore, I ended up implementing ActionListener AND Action. I also have to implement two abstract methods from Action.
Did I miss anything? Does the JPanel really need to implement Action? Why can't I cast an ActionListener class to Action?
Finally, is there a more elegant solution?
Thank you in advance.

Answer 1

Hi,
Hi Shannon,
Another problem... When we use
registerKeyboardAction() for a toolbar button, its
tool tip displays the key stroke used along with any
text you may have set as the tool tip. So if I have
JButton oBtn = new JButton();
oBtn.setIcon(new ImageIcon("SomeIcon.gif"));
oBtn.setToolTipText("Button Tool Tip");
oBtn.registerKeyboardAction(handler, null,
KeyStroke.getKeyStroke(KeyEvent.VK_N,
InputEvent.CTRL_MASK,
true),
JComponent.WHEN_IN_FOCUSED_WINDOW);when I try to view the tool tip, I actually see
"Button Tool Tip Ctrl-N" with the 'Ctrl-N' in a
different font and color than the remaining text. But
when I use the getActionMap() and getInputMap()
methods, this extra information is not seen in the
tool tip.Actually, even using getActionMap() and getInputMap(), you will see the control text. For example, the following is the equivalent of your code using getActionMap() and getInputMap():
oBtn.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
        KeyStroke.getKeyStroke(KeyEvent.VK_N,
        InputEvent.CTRL_MASK,
        true), "handler");
oBtn.getActionMap().put("handler", new AbstractAction(.....));As you'll see, it also shows the Ctrl-N in the tooltip text.
Since this behavior has been around since the very early days of Swing, I cannot give you the exact reason for it. However, I suspect it was assumed at the time that if a keystroke is added to a component for WHEN_IN_FOCUSED_WINDOW, then that keystroke is one that will activate the component.
Now, can I ask why you're adding this keyboard action to the button? Since its WHEN_IN_FOCUSED_WINDOW, you could add it to the contentpane or the rootpane. It doesn't need to be on the button.
Any help in this case??? My team leader
would prefer a function that is said to be outdated
but works so much better, rather than some new fangled
technique that doesn't give the same help....Just so you know, here's the implementation of registerKeyboardAction:
public void registerKeyboardAction(ActionListener anAction,
                                   String aCommand,
                                   KeyStroke aKeyStroke,
                                   int aCondition) {
    InputMap inputMap = getInputMap(aCondition, true);
    if (inputMap != null) {
        ActionMap actionMap = getActionMap(true);
        ActionStandin action = new ActionStandin(anAction, aCommand);
        inputMap.put(aKeyStroke, action);
            if (actionMap != null) {
                actionMap.put(action, action);
    }What am I trying to say? That the old technique simply uses the new technique internally. And it creates an action per keystroke. You might want to reconsider moving over to the new technique. I'd be happy to address any concerns you might have.
Thanks,
Shannon Hickey (Swing Team)
>
PLEASE HELP!!!
Regards,
Shefali