Applets and the Java 1.0 Event Model

The AWT event model changed dramatically between Java 1.0 and 1.1. Chapter 11 described the Java 1.1 event-handling model exclusively, since the Java 1.0 event model is now deprecated. However, because there is still a (dwindling) installed base of web browsers that support only the Java 1.0 event model, applets are sometimes still written using this model. This section briefly describes Java 1.0 event handling and includes an example applet that uses the model.[1]

In Java 1.0, all events are represented by the java.awt.Event class. This class has a number of instance fields that describe the event. One of these fields, id, specifies the type of the event. Event defines a number of constants that are the possible values for the id field. The target field specifies the object (typically a Component) that generated the event, or on which the event occurred (i.e., the source of the event). The other fields may or may not be used, depending on the type of the event. For example, the x and y fields are defined when id is BUTTON_EVENT, but not when it is ACTION_EVENT. The arg field can provide additional type-dependent data.

Java 1.0 events are dispatched first to the handleEvent( ) method of the Component on which they occurred. The default implementation of this method checks the id field of the Event object and dispatches the most commonly used types of events to various type-specific methods, listed in Table 16-1.

Table 16-1. Java 1.0 event-processing ...

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