ej.fp.util

Class WidgetWithListener

java.lang.Object

ej.fp.Widget

ej.fp.util.WidgetWithListener

Direct Known Subclasses:

Button, Joystick, Pointer, Wheel

public abstract class WidgetWithListener
extends Widget

This extension of widget holds several methods to instanciate a listener to the widget.

This listener is set in the front panel file (*.fp) using the method setListenerClass(Class, String). This user listener (front panel project user class) is checked (exists, implements right interface or extends right class, can be instanciated etc.) before using it.

The listener must be instanciated in Widget.start() method calling the method newListener(Class). It should not be instanciated earlier because user code may call Device.getDevice(): this method throws an exception until the device is fully created.

Setting an user class (using setListenerClass(Class, String) is optional. When not set, this class asks to subclass to create a default listener. This default listener cannot be null. At least, it should describes the widget event printing something in the standard output stream (FrontPanel.out).

Nested Class Summary

Nested classes/interfaces inherited from class ej.fp.Widget

Widget.WidgetAttribute, Widget.WidgetDescription

Field Summary

Fields inherited from class ej.fp.Widget

DEFAULT_LABEL

Constructor Summary

Constructors

Constructor and Description
WidgetWithListener()

Method Summary

Modifier and Type	Method and Description
protected Object	newDefaultListener() Lets subclass creates a default listener.
protected <T> T	newListener(Class<T> expectedType) Creates a new listener which has to implement / extend the given type.
void	setListenerClass(Class<?> expectedType, String listenerClassName) Sets the listener class name (package + class).

Methods inherited from class ej.fp.Widget

dispose, finalizeConfiguration, getAbsoluteX, getAbsoluteY, getCurrentSkin, getFilter, getHeight, getLabel, getParent, getSkin, getWidth, getX, getY, isOver, repaint, repaint, setCurrentSkin, setFilter, setHeight, setLabel, setOverlay, setSkin, setWidth, setX, setY, showYourself, start

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

WidgetWithListener

public WidgetWithListener()

Method Detail

newDefaultListener

protected Object newDefaultListener()

Lets subclass creates a default listener. This method must not return null. The listener should at least prints some traces in the standard output stream.

Returns:

a default listener.

newListener

protected <T> T newListener(Class<T> expectedType)

Creates a new listener which has to implement / extend the given type.

First, the implementation tries to create the listener whose class name has been set by setListenerClass(Class, String). On class loading error, an exception is thrown: the user class must be valid.

If the user class name has not been set, the implementation asks the subclass to create a default listener. This listener must not be null and has to implement / extend given class.

Parameters:

expectedType - the class the listener has to implement / extend.

Returns:

the created listener.

setListenerClass

public void setListenerClass(Class<?> expectedType,
                             String listenerClassName)

Sets the listener class name (package + class). This class must exist otherwise an IllegalArgumentException is thrown.

Parameters:

expectedType - the class the listener has to implement or extends.

listenerClassName - the class name to load.