Java 6 Illuminated: An Active Learning Approach, 2nd Edition

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, ...