An example that shows lots of little UndoManager details
/*
Java Swing, 2nd Edition
By Marc Loy, Robert Eckstein, Dave Wood, James Elliott, Brian Cole
ISBN: 0-596-00408-7
Publisher: O'Reilly
*/
// UndoManagerDetails.java
//An example that shows lots of little UndoManager details
//
import java.util.Enumeration;
import java.util.Vector;
import javax.swing.undo.AbstractUndoableEdit;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;
import javax.swing.undo.UndoableEdit;
public class UndoManagerDetails {
public static void main(String[] args) {
UndoManager mgr = new UndoManager();
// Show how insignificant edits are skipped over.
//
// # adds? sig? replace?
mgr.addEdit(new SampleUndoableEdit(1, false, true, false));
mgr.addEdit(new SampleUndoableEdit(2, false, true, false));
mgr.addEdit(new SampleUndoableEdit(3, false, false, false));
mgr.addEdit(new SampleUndoableEdit(4, false, false, false));
System.out.println("--------------------------");
System.out.println("Insignificant edit example");
System.out.println("--------------------------");
mgr.undo();
mgr.redo();
System.out.println(mgr.canRedo()); // No more sig. edits
// Show how edits that call add/replace are used.
//
// # adds? sig? replace?
mgr.addEdit(new SampleUndoableEdit(5, true, true, false));
mgr.addEdit(new SampleUndoableEdit(6, false, true, false));
System.out.println("----------------------------------");
System.out.println("Absorbed (by addEdit) edit example");
System.out.println("----------------------------------");
mgr.undo();
mgr.discardAllEdits();
// # adds? sig? replace?
mgr.addEdit(new SampleUndoableEdit(1, false, true, false));
mgr.addEdit(new SampleUndoableEdit(2, false, true, true));
System.out.println("--------------------------------------");
System.out.println("Absorbed (by replaceEdit) edit example");
System.out.println("--------------------------------------");
mgr.undo();
System.out.println(mgr.canUndo());
// Show how changing limit works.
mgr.discardAllEdits();
// # adds? sig? replace?
mgr.addEdit(new SampleUndoableEdit(1, false, true, false));
mgr.addEdit(new SampleUndoableEdit(2, false, true, false));
mgr.addEdit(new SampleUndoableEdit(3, false, true, false));
mgr.addEdit(new SampleUndoableEdit(4, false, true, false));
mgr.addEdit(new SampleUndoableEdit(5, false, true, false));
mgr.addEdit(new SampleUndoableEdit(6, false, true, false));
System.out.println("----------------------");
System.out.println("Changing limit example");
System.out.println("----------------------");
mgr.undo();
mgr.undo();
mgr.undo(); // Now 3 undoable, 3 redoable
mgr.setLimit(4); // Now 2 undoable, 2 redoable!
while (mgr.canUndo())
mgr.undo();
while (mgr.canRedo())
mgr.redo();
// undoOrRedo example
mgr.discardAllEdits();
mgr.setLimit(1);
// # adds? sig? replace?
mgr.addEdit(new SampleUndoableEdit(1, false, true, false));
System.out.println("------------------");
System.out.println("undoOrRedo example");
System.out.println("------------------");
System.out.println(mgr.getUndoOrRedoPresentationName());
mgr.undoOrRedo();
System.out.println(mgr.getUndoOrRedoPresentationName());
mgr.undoOrRedo();
// Show how UndoManager becomes a CompositeEdit.
mgr.discardAllEdits();
mgr.setLimit(100);
// # adds? sig? replace?
mgr.addEdit(new SampleUndoableEdit(1, false, true, false));
mgr.addEdit(new SampleUndoableEdit(2, false, true, false));
mgr.addEdit(new SampleUndoableEdit(3, false, true, false));
System.out.println("------------------------------");
System.out.println("Transform to composite example");
System.out.println("------------------------------");
mgr.end();
mgr.undo();
mgr.redo();
// Show that adds are no longer allowed. Note that addEdit() returns
// true in
// pre-JDK 1.2 Swing releases. This is fixed in JDK 1.2.
System.out.println(mgr.addEdit(new SampleUndoableEdit(4, false, true,
false)));
mgr.undo(); // note that edit 4 is not there
}
}
//SampleUndoableEdit.java
//A simple (?) example of an undoable edit.
//
class SampleUndoableEdit extends AbstractUndoableEdit {
private boolean isSignificant;
private boolean isReplacer;
private int number;
private boolean allowAdds;
private Vector addedEdits;
private UndoableEdit replaced;
// Create a new edit with an identifying number. The boolean arguments
// define
// the edit's behavior.
public SampleUndoableEdit(int number, boolean allowAdds,
boolean isSignificant, boolean isReplacer) {
this.number = number;
this.allowAdds = allowAdds;
if (allowAdds)
addedEdits = new Vector();
this.isSignificant = isSignificant;
this.isReplacer = isReplacer;
}
// "Undo" the edit by printing a message to the screen.
public void undo() throws CannotUndoException {
super.undo();
System.out.print("Undo " + number);
dumpState();
}
// "Redo" the edit by printing a message to the screen.
public void redo() throws CannotRedoException {
super.redo();
System.out.print("Redo " + number);
dumpState();
}
// If allowAdds is true, we store the input edit. If not, just return false.
public boolean addEdit(UndoableEdit anEdit) {
if (allowAdds) {
addedEdits.addElement(anEdit);
return true;
} else
return false;
}
// If isReplacer is true, we store the edit we are replacing.
public boolean replaceEdit(UndoableEdit anEdit) {
if (isReplacer) {
replaced = anEdit;
return true;
} else
return false;
}
// Significance is based on constructor parameter.
public boolean isSignificant() {
return isSignificant;
}
// Just return our identifier.
public String toString() {
return "<" + number + ">";
}
// Debug output.
public void dumpState() {
if (allowAdds && addedEdits.size() > 0) {
Enumeration e = addedEdits.elements();
System.out.print(" (absorbed: ");
while (e.hasMoreElements()) {
System.out.print(e.nextElement());
}
System.out.print(")");
}
if (isReplacer && replaced != null) {
System.out.print(" (replaced: " + replaced + ")");
}
System.out.println();
}
}
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