* needs-more-work: canDoIt, canUndoIt predicates control graying.
* needs-more-work: Editor will keep a history of recent actions for * undo.
* * FEATURE: editing_actions * * FEATURE: undo_and_redo * @see Editor * @see ExecuteActionWindow */ public abstract class Action implements GEF { //////////////////////////////////////////////////////////////// // instance variables /** Arguments that configure the Action instance. */ protected Hashtable _args; //////////////////////////////////////////////////////////////// // constructors /** Construct a new Action with the given arguments */ public Action(Hashtable args) { _args = args; } /** Construct a new Action with no arguments */ public Action() { this(null); } //////////////////////////////////////////////////////////////// // accessors /** Return a name for this action suitable for display to the user */ public String name() { return this.getClass().getName(); } /** Get the object stored as an argument under the given name. */ protected Object getArg(String key) { if (_args == null) return null; else return _args.get(key); } /** Get an argument by name. If it's not defined then use the given * default. */ protected Object getArg(String key, Object defaultValue) { if (_args == null) return defaultValue; Object res = _args.get(key); if (res == null) return defaultValue; return res; } /** Store the given argument under the given name. */ protected void setArg(String key, Object value) { if (_args == null) { _args = new Hashtable(); } _args.put(key, value); } /** Reply true if this Action instance has the named argument defined. */ protected boolean containsArg(String key) { return _args != null && _args.containsKey(key); } //////////////////////////////////////////////////////////////// // Action API /** Return a URL that has user and programmer documentation. * * FEATURE: view_action_documentation */ public String about() { return "http://www.ics.uci.edu/~jrobbins/gef/Docs.html#" + getClass().getName(); } /** Perform whatever action this Action is meant to do. Subclasses * should override this to do whatever is intended. When the action * executes, it should store enough information to undo itself later * if needed. * @param e The event that caused this Action to be * performed. Generally it is a bad idea to depend on the * contents of this event too much. */ public abstract void doIt(java.awt.Event e); /** Undo the action using information stored during its * execution.
* needs-more-work: This is not currently implemented. */ public abstract void undoIt(); // needs-more-work: do I need a separate redo()? Should doIt() take // flag to indicate if this is the first time the action is being // done, or it it is actually being redone? What information does // undoIt() need to store to support redo? //////////////////////////////////////////////////////////////// // registered actions /** A list of Action instances that should appear in lists for the * user to pick from. Registered actions server mainly to support * user interface prototyping: you can add actions to the * ExecuteActionWindow and not have to woory about where it should * eventually go in the user interface. */ private static Vector _registeredActions = new Vector(); /** Return a list of "well-known" Action instances that should * appear in lists for the user to pick from. * @see ExecuteActionWindow */ public static Enumeration registeredActions() { return _registeredActions.elements(); } /** Add a "well-known" Action */ public static void register(Action a) { _registeredActions.addElement(a); } /** Return the "well-known" action at a given index. Useful for * displaying a list of "well-known" actions. */ public static Action actionAtIndex(int i) { return (Action) _registeredActions.elementAt(i); } } /* end class Action */