javax.swing.undo: public class: StateEdit

javax.swing.undo
public class: StateEdit [javadoc | source]

java.lang.Object
   javax.swing.undo.AbstractUndoableEdit
      javax.swing.undo.StateEdit

All Implemented Interfaces:
UndoableEdit, Serializable

StateEdit is a general edit for objects that change state. Objects being edited must conform to the StateEditable interface.

This edit class works by asking an object to store it's state in Hashtables before and after editing occurs. Upon undo or redo the object is told to restore it's state from these Hashtables.

A state edit is used as follows:

     // Create the edit during the "before" state of the object
     StateEdit newEdit = new StateEdit(myObject);
     // Modify the object
     myObject.someStateModifyingMethod();
     // "end" the edit when you are done modifying the object
     newEdit.end();

Note that when a StateEdit ends, it removes redundant state from the Hashtables - A state Hashtable is not guaranteed to contain all keys/values placed into it when the state is stored!

Also see:

StateEditable

author: Ray - Ryan

Field Summary
protected static final String	RCSID
protected StateEditable	object	The object being edited
protected Hashtable<Object, Object>	preState	The state information prior to the edit
protected Hashtable<Object, Object>	postState	The state information after the edit
protected String	undoRedoName	The undo/redo presentation name

Fields inherited from javax.swing.undo.AbstractUndoableEdit:
UndoName, RedoName, hasBeenDone, alive

Constructor:

Constructor:
public StateEdit(StateEditable anObject) { super(); init (anObject,null); } Create and return a new StateEdit. Parameters: `anObject` - The object to watch for changing state Also see: StateEdit
public StateEdit(StateEditable anObject, String name) { super(); init (anObject,name); } Create and return a new StateEdit with a presentation name. Parameters: `anObject` - The object to watch for changing state `name` - The presentation name to be used for this edit Also see: StateEdit

 public StateEdit(StateEditable anObject) {
        super();
        init (anObject,null);
}

Create and return a new StateEdit.

Parameters:

anObject - The object to watch for changing state

Also see:

StateEdit

 public StateEdit(StateEditable anObject,
    String name) {
        super();
        init (anObject,name);
}

Create and return a new StateEdit with a presentation name.

Parameters:

anObject - The object to watch for changing state

name - The presentation name to be used for this edit

Also see:

StateEdit

Method from javax.swing.undo.StateEdit Summary:
end, getPresentationName, init, redo, removeRedundantState, undo

Methods from javax.swing.undo.AbstractUndoableEdit:
addEdit, canRedo, canUndo, die, getPresentationName, getRedoPresentationName, getUndoPresentationName, isSignificant, redo, replaceEdit, toString, undo

Methods from java.lang.Object:
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from javax.swing.undo.StateEdit Detail:
public void end() { this.postState = new Hashtable< Object, Object >(11); this.object.storeState(this.postState); this.removeRedundantState(); } Gets the post-edit state of the StateEditable object and ends the edit.
public String getPresentationName() { return this.undoRedoName; } Gets the presentation name for this edit
protected void init(StateEditable anObject, String name) { this.object = anObject; this.preState = new Hashtable< Object, Object >(11); this.object.storeState(this.preState); this.postState = null; this.undoRedoName = name; }
public void redo() { super.redo(); this.object.restoreState(postState); } Tells the edited object to apply the state after the edit
protected void removeRedundantState() { Vector< Object > uselessKeys = new Vector< Object >(); Enumeration myKeys = preState.keys(); // Locate redundant state while (myKeys.hasMoreElements()) { Object myKey = myKeys.nextElement(); if (postState.containsKey(myKey) && postState.get(myKey).equals(preState.get(myKey))) { uselessKeys.addElement(myKey); } } // Remove redundant state for (int i = uselessKeys.size()-1; i >= 0; i--) { Object myKey = uselessKeys.elementAt(i); preState.remove(myKey); postState.remove(myKey); } } Remove redundant key/values in state hashtables.
public void undo() { super.undo(); this.object.restoreState(preState); } Tells the edited object to apply the state prior to the edit

Method from javax.swing.undo.StateEdit Detail:

 public  void end() {
        this.postState = new Hashtable< Object, Object >(11);
        this.object.storeState(this.postState);
        this.removeRedundantState();
}

Gets the post-edit state of the StateEditable object and ends the edit.

 public String getPresentationName() {
        return this.undoRedoName;
}

Gets the presentation name for this edit

 protected  void init(StateEditable anObject,
    String name) {
        this.object = anObject;
        this.preState = new Hashtable< Object, Object >(11);
        this.object.storeState(this.preState);
        this.postState = null;
        this.undoRedoName = name;
}

 public  void redo() {
        super.redo();
        this.object.restoreState(postState);
}

Tells the edited object to apply the state after the edit

 protected  void removeRedundantState() {
        Vector< Object > uselessKeys = new Vector< Object >();
        Enumeration myKeys = preState.keys();
        // Locate redundant state
        while (myKeys.hasMoreElements()) {
            Object myKey = myKeys.nextElement();
            if (postState.containsKey(myKey) &&
                postState.get(myKey).equals(preState.get(myKey))) {
                uselessKeys.addElement(myKey);
            }
        }
        // Remove redundant state
        for (int i = uselessKeys.size()-1; i  >= 0; i--) {
            Object myKey = uselessKeys.elementAt(i);
            preState.remove(myKey);
            postState.remove(myKey);
        }
}

Remove redundant key/values in state hashtables.

 public  void undo() {
        super.undo();
        this.object.restoreState(preState);
}

Tells the edited object to apply the state prior to the edit