Adapter Classes Java provides a special feature, called an adapter class, that call simplify the creation of event handlers in certain situations. An adapter class provides an empty implementation of all me mods in an event listener interface. Masterclasses are useful when you want to receive and process only some of the events that are handled by a…
Handling Mouse Events To handle mouse events, you must implement tile Mouse Listener and the Mouse Motion Listener interfaces. The following applet demonstrates the process. It displays the current coordinates of the mouse in the applet’s status window. Each lime .a button is pressed, the word ‘.’Down” is displayed at the location of the mouse pointer. Each time the…
EVENT LISTENER INTERFACE As explained, the delegation event model has two parts: sources and listeners. Listeners are created by implementing one or more of the interfaces defined by the java awt event package. When an event occurs, the event source invokes the appropriate method defined by the listener and provides an event object as its argument. Table 20-3…
The Mouse Event Class There are seven types of mouse events. The Mouse Event class defines the following integer constants that can be used to identify them: Here, src is a reference to the component that generated the event. The type of the event is specified by type. The system time at which the mouse event…
The Container Event Class A Focus Event is generated when a component gains or loses input focus. These events are identified by the integer constants FOCUS_GAINED and FOCUS_LOST. Focus Event is a subclass of Component Event and has these constructors: Event(Component int type) Focus Event(Component Flag Here, is a reference to the component that generated this event. The type…
Events In the delegation model, an cu cut is an object that describes a stall’ change in a source. It can be generated as a consequence of a person interacting with the elements in a graphical user interface. Some of the activities that cause events to be generated are pressing a button, entering a character via the keyboard,…
Event Handling T’his cpapter examines an important aspect of Java that relates to’ applet events. As explained in Chapter 19, applets are event-driven programs. Thus, event handling is at the core of successful applet programming. Most events to which your appletwill respond are generated by the user. These events are passed to your applet in a variety of ways,…
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