Java Reference
In-Depth Information
public UndoableDrawingPanel() {
MouseListener mouseListener = new MouseAdapter() {
public void mouseReleased(MouseEvent mouseEvent) {
undoableEditSupport.postEdit(
new UndoableDrawEdit(UndoableDrawingPanel.this));
polygon.addPoint(mouseEvent.getX(), mouseEvent.getY());
repaint();
}
};
addMouseListener(mouseListener);
}
public void addUndoableEditListener(
UndoableEditListener undoableEditListener) {
undoableEditSupport.addUndoableEditListener(undoableEditListener);
}
public void removeUndoableEditListener(
UndoableEditListener undoableEditListener) {
undoableEditSupport.removeUndoableEditListener(undoableEditListener);
}
public void setPolygon(Polygon newValue) {
polygon = newValue;
repaint();
}
public Polygon getPolygon() {
Polygon returnValue;
if (polygon.npoints == 0) {
returnValue = new Polygon();
} else {
returnValue = new Polygon(
polygon.xpoints, polygon.ypoints, polygon.npoints);
}
return returnValue;
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawPolygon(polygon);
}
}
When defining the custom implementation of the
UndoableEdit
interface, you can choose
to implement the complete interface, or you can subclass the
AbstractUndoableEdit
class and
override any appropriate methods. More typically, you'll just subclass
AbstractUndoableEdit
.
