怎么写重做和撤消的代码？

Question

javax.swing.undo包下面有这方面的类，你看一下。《java2图形设计卷IISWING》P895有例子。

Answer 1

从我的一个程序中节选过来，你应该看得懂protected UndoManager undo = new UndoManager();
protected ActionListener undoRedo = new DocumentUndoRedoManager();textArea.getDocument().addUndoableEditListener((UndoableEditListener));
toolBar.undoButton.addActionListener(undoRedo);
toolBar.undoButton.setActionCommand(UNDO_COMMAND);
........//an inner class
     class DocumentUndoRedoManager implements UndoableEditListener, ActionListener{
public void undoableEditHappened(UndoableEditEvent e){
undo.addEdit(e.getEdit());
check();
}
public void actionPerformed(ActionEvent e){
String cmd = e.getActionCommand();
if(cmd.equals(UNDO_COMMAND)){
undo.undo();
}else if(cmd.equals(REDO_COMMAND)){
undo.redo();
}
check();
textArea.requestFocus();
}
public void check(){
boolean canUndo=undo.canUndo(), canRedo=undo.canRedo();
menuBar.undoMenuItem.setEnabled(canUndo);
menuBar.redoMenuItem.setEnabled(canRedo);
toolBar.undoButton.setEnabled(canUndo);
toolBar.redoButton.setEnabled(canRedo);
}
}