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Copyright © 2006 Sun Microsystems, Inc. All rights reserved.

Package javax.microedition.xlet

Provides interfaces used by applications and the application manager to communicate.

See:
Description

Interface Summary

Xlet	This interface allows an application manager to create, initialize, start, pause, and destroy an Xlet.
XletContext	An interface that provides methods allowing an Xlet to discover information about its environment.

Exception Summary

UnavailableContainerException	Signals that no Container can be provided for the Xlet to use at this time.
XletStateChangeException	Signals that a requested Xlet state change failed.

Package javax.microedition.xlet Description

Provides interfaces used by applications and the application manager to communicate. This package defines two entities: the Xlet and the XletContext. The central function of this set of interfaces is to model and manage the states an application can be in. Xlet is an interface that must be implemented by the primary class of an application. When an application is loaded, one instance of this primary class is created. The application is controlled via method calls on this instance. Methods of Xlet are used by the application manager to deliver state change requests to the application. An application is provided with an instance of XletContext, which it can use to deliver state change notifications to the application manager. Each Xlet receives its own instance of XletContext. An application might have a graphical representation, or it might be a headless "service."

This interface allows an application manager to create, initialize, start, pause, and destroy an application.

The following is a description of the Xlet state model. Note that an Xlet is not required to maintain an explicit internal model of its state; however it must nonetheless behave as described by the following model.

State Name	Description
Loaded	The application has been loaded but has not been initialized. This state is entered: After the application's Xlet instance has been created. This causes the xlet's no-argument constructor to be called. The application typically does little or no initialization in this step. If an exception is thrown from the constructor, the application is considered to be destroyed; it will receive no further Xlet callbacks, and its resources will be eligible for reclamation. Note: This state is entered only once per application instance.
Paused	The application is initialized and quiescent. It should keep itself ready to become active quickly. As a secondary goal, it should attempt to minimize resource usage. This state is entered: From the Loaded state after the initXlet method returns successfully. From the Active state after the pauseXlet method returns successfully. From the Active state upon entering the XletContext.notifyPaused method.
Active	The application is functioning normally and executing. This state is entered: From the Paused after the startXlet() method returns successfully. Note: Applications that are in the Paused state may identify to the application manager that they would like to be brought into the Active state by calling XletContext.resumeRequest. Calling this method provides no guarantee that their startXlet method will be called.
Destroyed	The application has released all of its resources and terminated. This state is entered: When the Xlet's destroyXlet() method returns successfully. The destroyXlet() method shall release all resources held and perform any necessary clean up so the application may be garbage collected. Upon entering the XletContext.notifyDestroyed() method. The Xlet perform its clean up actions before calling the notifyDestroyed() method. When the Xlet fails to respond to a state change notification within a reasonable amount of time. The precise length of time is implementation dependent. Note: This state is only entered once, and is the terminal state. Once an application is in the destroyed state, all of its resources are eligible for reclamation.

This Profile supports the simultaneous execution of multiple Xlets. Each xlet is loaded by a unique class loader, and receives a distinct copy of each user defined class. Therefore it is impossible for xlets to communicate by sharing instances through static data members of user defined classes.

If a suitable API is available on the target platform, applications may create their own additional classloaders. Each such classloader must have its application's classloader as an ancestor.