
12.13 Layout Managers: GridLayout 887
At lines 21–23, we register this TreasureHunt object on itself as a Mouse-
MotionListener. In this game, the only event we want to handle is the user
moving the mouse. Because TreasureHuntClient implements the Mouse-
MotionListener interface, however, we must implement both the mouse-
Moved and the mouseDragged methods. We are interested in the
mouseMoved method only; thus, we implement mouseDragged with an
empty body (lines 29–30). Note that we could not use the MouseMotion-
Adapter class because our application (which is the listener) already
extends the JFrame class. Remember that a class can extend only one class, ...