Java AWT: Delegation Event Model
Your problem requires some study of the Delegation Event Model Please adjust your displayed name to meet the import 572233.info In the event delegation model, a class represents each event type. Event objects are all defined in the 572233.infobject subclasses. Event Delegation. • Java runtime system generates events. (AWTEvent objects) when user does something with mouse or keyboard. • UI components (event.
TableCellRenderer An interface that a class must implement if its objects are to render table component cells.
Event delegation ~ Java Tutorials
TableColumn A class whose objects describe the attributes such as width, editor, and renderer of individual table component columns. TableColumnModel An interface that a class must implement if its objects are to manage the columns of various table components. TableModel An interface that a class must implement if its objects are to manage the cell values of various table components.
BasicLookAndFeel The base class of all look-and-feel classes. Among other things, BasicLookAndFeel associates keystroke names with tasks that a table component must perform such as initiating an editing session. After reading Table 1, you might be wondering what the terms look and feel and UI delegates mean. The next section explores those terms.
As you will discover, the concepts of look and feel and UI delegates are important to understanding the architecture of table components. That architecture splits a component into a model, one or more views, and a controller.
A component's state is maintained by a model. For example, button press information is maintained by a button model. A visual representation of that model's state is provided by a view. The view gives a component its look. For example, a button view draws a button so that it appears to be either pressed or not pressed, depending on the press information contained in the model. The controller determines whether a component can respond to input events that originate from input devices such as keyboards and miceand it gives a component its feel.
For example, when you press a mouse button over some view of a button component, the button component's controller contacts the button component's model to have that model update itself. In turn, the model contacts the button component's view with a request for the view to redraw itself.Java Programming Tutorial - 52 - Event Handling
It is much easier to customize a component by changing its model, view, or controller than it is to change the entire component. To change a Swing component's model, either Swing usually through a constructor or your own code calls that component's setModel method. For example, the JTable class declares a setModel TableModel m method that either you or one of JTable's constructors calls to establish a table component's model.
The TableModel interface argument m references the object that will serve as that model.
- Exploring Swing's Table Component
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The listener is responsible for generating a response to an event. From the point of view of Java implementation, the listener is also an object. The listener waits till it receives an event.
SWING - Event Handling
Once the event is received, the listener processes the event and then returns. The benefit of this approach is that the user interface logic is completely separated from the logic that generates the event. The user interface element is able to delegate the processing of an event to a separate piece of code.
In this model, the listener needs to be registered with the source object so that the listener can receive the event notification. This is an efficient way of handling the event because the event notifications are sent only to those listeners who want to receive them. Points to Remember About the Listener In order to design a listener class, you have to develop some listener interfaces.
These Listener interfaces forecast some public abstract callback methods, which must be implemented by the listener class. If you do not implement any of the predefined interfaces, then your class cannot act as a listener class for a source object.
Understanding and Using the Java Delegation Event Model
Callback Methods These are the methods that are provided by API provider and are defined by the application programmer and invoked by the application developer. Here the callback methods represent an event method.
In response to an event, java jre will fire callback method. All such callback methods are provided in listener interfaces. If a component wants some listener to listen ot its events, the source must register itself to the listener. Run the program using the following command.