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JDK 1.1 Event Examples

This simple demo contains four applets that get progressively better at handling events. The final result is a simple-minded game.

This code was used in Hans Muller's exposition on 1.1 event handling, which was part of the AWT Advanced Tutorial at JavaOne.

Note: The following applets rely on 1.1 code. They do not run in 1.0-based browsers. You can run them in the latest JDK Applet Viewer or HotJava.

Using Anonymous Classes to Implement an Event Listener

The red box at the bottom of the game screen tracks the mouse because the panel that contains is handling MouseMotion events. The handler is an anonymous class that implements MouseMotionListener.

Using a Static Nested Class to Implement an Event Listener

Each column of boxes, the targets, at the top of the game screen is a Panel. By adding a listener that handles enter/exit events to each panel we can make it highlight when the mouse passes over. In this case we've used instances of a static listener class to handle the enter/exit events. Unfortunately there's a bug here: the red "puck" isn't tracking the mouse correctly anymore!

Redispatching Events to Another Component

The target panels are consuming (and discarding) the MouseMotion events that should be delivered to the game Panel. To redispatch the events we translate their coordinates to the Panels origin and pass them along with dispatchEvent().

Complete Example

Click the mouse as many times as there are boxes in a column to get a satisfying "beep" and to make the boxes disappear. To win the game clear the entire panel. If you find yourself playing this game more than once, seek professional help immediately.

Hans Muller

Last modified: Tue Mar 11 11:33:42 PST