How to use Action/Input maps

Question

It seems to me that the move to sharing actions menus, buttons, and other components is a logical one, given that it is desirable to have all references to the action reflect its enabled state.
The question that arises is: which ActionMap object to use as the central store? Do you create your own and pass it on somewhere?
And, if you try to do anything with homegrown InputMaps then the components stop seeing the events. I wish there was a definitive YOU MUST DO IT THIS WAY tutorial.
Why is there no factory API that can create UI components pre-attached to actions and with accelerators or mnemonics already set? Then we would not need to write half the code we do now. My solution:
public class ComponentFactory {
   ActionMap myMap;
   public ComponentFactory(ActionMap map) {
      myMap = map;
   public JButton createButton(String actioncommand) {
       Action a = myMap.get(actioncommand)
       if(a==null)
          return null;
       return new JButton(a);
   public JMenuItem createMenuItem(String actioncommand) {
    // etc...
   public void setAction(Action a) {
       myMap.put(a.getValue(ACTION_COMMAND_KEY),a);
   public void setEnabled(String actioncommand, boolean state) {
       Action a = myMap.get(actioncommand);
       if(a!=null)
           a.setEnabled(state);
}Is there any concensus as to the best way to handle ActionMaps/InputMaps?

Answer 1

Hugh,
>
The tutorial is a touch short on this subject, whilst
it is good on how to create and use actions with
toolbars and the like, the section on InputMaps and
ActionMaps is far too brief to get the wider picture.
The API docs on the same is about one paragraph's
worth.okay, I just checked the tutorial - it's a bit short on the inputMap/actionMap indeed.
>
You are mixing up two different issues:
a) customize a button with an action
b) bind a keyStroke to an action for an arbitrary
jComponent
a) has nothing to do with b)If b) has nothing to do with a) why have MNEMONIC_KEY
and ACCELERATOR_KEY on the action?Hmm... where do you see a contradiction to my statement? Those keys are part of a) as they are used for customization of the AbstractButtons: the button's mnenmonic/accelerator properties are set to the corresponding values of the action. This propertyChange triggers an update of the keyBinding to the button's "pressed"/"doClick" actions as registered in the actionMap. They are never used (at least not internally by Swing) for b)
Historically the action is older than the inputMap/actionMap: basically it's an ActionListener (which is more or less a command pattern) plus some (view) state. This "plus" was designed right in the beginning of Swing for a) to enable state sharing between different "buttons" but not really integrated until version 1.4. parallel to that the need for a general mechanism of binding between keyStrokes and "commands" became obvious and inputMap/actionMap were introduced in 1.3. The only action state that's needed for this mechanism to work is the enabled property. All values are ignored - so currently they somehow appear to be overloaded in the context of the inputMap/actionMap. Personally I think they are very powerful because of this extra flexibility.
>
There is still not a single diagram; and I maintain
that it is less than useful to beginners who are not
familiar with the terminology used. Well, IMO diagrams are not everything - I still think it much easier to understand than the dnd spec or the focus spec f.i.
>
you are free to use whatever object you want as akey
- write a utility method to use the name, if feellike
doeing so. There is nothing in the framework that
would single out the name as "the" key to use, The keybindings document specifically states:
"New actions can be added to a component equally
easily."
"The conventional key for an action is it's
name." If there is a conventional way then it
should be encouraged with an appropriate API. I get your point. And I definitely agree on following a convention if there is one. Except when the convention is quite immature (to formulate mildly) - and not even followed by Swing internally: most of the default actions registered in the actionMap don't even have a name, the binding is done by string literals ... duplicated in at least two places: the XXLookAndFeel and the ui-delegates.
Greetings
Jeanette