Construct a GUI that demonstrates use of UndoManager
Container cp = getContentPane();
cp.add(ta = new JTextArea(20, 60), BorderLayout.CENTER);
JPanel bp;
cp.add(bp = new JPanel(), BorderLayout.SOUTH);
// Create a javax.swing.undo.UndoManager; this is an amazing class that
// keeps a Stack of UndoableEdits and lets you invoke them;
// by registering it as a Listener on the TextComponent.Document,
// the Document will create the UndoableEdit objects and send them
// to the UndoManager. Between them they do ALL the work!
um = new UndoManager();
ta.getDocument().addUndoableEditListener(um);
// Create the buttons
JButton cutButton, copyButton, pasteButton, undoButton, redoButton;
bp.add(cutButton = new JButton("Cut"));
cutButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
ta.cut();
}
});
bp.add(copyButton = new JButton("Copy"));
copyButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
ta.copy();
}
});
bp.add(pasteButton = new JButton("Paste"));
pasteButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
ta.paste();
}
});
bp.add(undoButton = new JButton("UnDo"));
undoButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (um.canUndo()) {
um.undo();
} else {
warn("Can't undo");
}
}
});
bp.add(redoButton = new JButton("ReDo"));
redoButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (um.canRedo()) {
um.redo();
} else {
warn("Can't redo");
}
}
});
pack();
setDefaultCloseOperation(EXIT_ON_CLOSE);
