UndoableEdit,
* implementing simple responses to all boolean methods in
* that interface.
*
* @author Ray Ryan
*/
public class AbstractUndoableEdit implements UndoableEdit, Serializable {
private static final long serialVersionUID = 580150227676302096L;
/**
* String returned by getUndoPresentationName;
* as of Java 2 platform v1.3.1 this field is no longer used. This value
* is now localized and comes from the defaults table with key
* AbstractUndoableEdit.undoText.
*
* @see javax.swing.UIDefaults
*/
protected static final String UndoName = "Undo";
/**
* String returned by getRedoPresentationName;
* as of Java 2 platform v1.3.1 this field is no longer used. This value
* is now localized and comes from the defaults table with key
* AbstractUndoableEdit.redoText.
*
* @see javax.swing.UIDefaults
*/
protected static final String RedoName = "Redo";
/**
* Defaults to true; becomes false if this edit is undone, true
* again if it is redone.
*/
boolean hasBeenDone;
/**
* True if this edit has not received die; defaults
* to true.
*/
boolean alive;
/**
* Creates an AbstractUndoableEdit which defaults
* hasBeenDone and alive to true.
*/
public AbstractUndoableEdit() {
super();
hasBeenDone = true;
alive = true;
}
/**
* Sets alive to false. Note that this
* is a one way operation; dead edits cannot be resurrected.
* Sending undo or redo to
* a dead edit results in an exception being thrown.
*
* Typically an edit is killed when it is consolidated by
* another edit's addEdit or replaceEdit
* method, or when it is dequeued from an UndoManager.
*/
public void die() {
alive = false;
}
/**
* Throws CannotUndoException if canUndo
* returns false. Sets hasBeenDone
* to false. Subclasses should override to undo the
* operation represented by this edit. Override should begin with
* a call to super.
*
* @exception CannotUndoException if canUndo
* returns false
* @see #canUndo
*/
public void undo() throws CannotUndoException {
if (!canUndo()) {
throw new CannotUndoException();
}
hasBeenDone = false;
}
/**
* Returns true if this edit is alive
* and hasBeenDone is true.
*
* @return true if this edit is alive
* and hasBeenDone is true
*
* @see #die
* @see #undo
* @see #redo
*/
public boolean canUndo() {
return alive && hasBeenDone;
}
/**
* Throws CannotRedoException if canRedo
* returns false. Sets hasBeenDone to true.
* Subclasses should override to redo the operation represented by
* this edit. Override should begin with a call to super.
*
* @exception CannotRedoException if canRedo
* returns false
* @see #canRedo
*/
public void redo() throws CannotRedoException {
if (!canRedo()) {
throw new CannotRedoException();
}
hasBeenDone = true;
}
/**
* Returns true if this edit is alive
* and hasBeenDone is false.
*
* @return true if this edit is alive
* and hasBeenDone is false
* @see #die
* @see #undo
* @see #redo
*/
public boolean canRedo() {
return alive && !hasBeenDone;
}
/**
* This default implementation returns false.
*
* @param anEdit the edit to be added
* @return false
*
* @see UndoableEdit#addEdit
*/
public boolean addEdit(UndoableEdit anEdit) {
return false;
}
/**
* This default implementation returns false.
*
* @param anEdit the edit to replace
* @return false
*
* @see UndoableEdit#replaceEdit
*/
public boolean replaceEdit(UndoableEdit anEdit) {
return false;
}
/**
* This default implementation returns true.
*
* @return true
* @see UndoableEdit#isSignificant
*/
public boolean isSignificant() {
return true;
}
/**
* This default implementation returns "". Used by
* getUndoPresentationName and
* getRedoPresentationName to
* construct the strings they return. Subclasses should override to
* return an appropriate description of the operation this edit
* represents.
*
* @return the empty string ""
*
* @see #getUndoPresentationName
* @see #getRedoPresentationName
*/
public String getPresentationName() {
return "";
}
/**
* Retreives the value from the defaults table with key
* AbstractUndoableEdit.undoText and returns
* that value followed by a space, followed by
* getPresentationName.
* If getPresentationName returns "",
* then the defaults value is returned alone.
*
* @return the value from the defaults table with key
* AbstractUndoableEdit.undoText, followed
* by a space, followed by getPresentationName
* unless getPresentationName is "" in which
* case, the defaults value is returned alone.
* @see #getPresentationName
*/
public String getUndoPresentationName() {
String name = getPresentationName();
if (!"".equals(name)) {
name = UIManager.getString("AbstractUndoableEdit.undoText") +
" " + name;
} else {
name = UIManager.getString("AbstractUndoableEdit.undoText");
}
return name;
}
/**
* Retreives the value from the defaults table with key
* AbstractUndoableEdit.redoText and returns
* that value followed by a space, followed by
* getPresentationName.
* If getPresentationName returns "",
* then the defaults value is returned alone.
*
* @return the value from the defaults table with key
* AbstractUndoableEdit.redoText, followed
* by a space, followed by getPresentationName
* unless getPresentationName is "" in which
* case, the defaults value is returned alone.
* @see #getPresentationName
*/
public String getRedoPresentationName() {
String name = getPresentationName();
if (!"".equals(name)) {
name = UIManager.getString("AbstractUndoableEdit.redoText") +
" " + name;
} else {
name = UIManager.getString("AbstractUndoableEdit.redoText");
}
return name;
}
/**
* Returns a string that displays and identifies this
* object's properties.
*
* @return a String representation of this object
*/
public String toString()
{
return super.toString()
+ " hasBeenDone: " + hasBeenDone
+ " alive: " + alive;
}
}