javax.microedition.xlet

Interface XletContext

public interface XletContext

An interface that provides methods allowing an Xlet to discover information about its environment. An XletContext is passed to an Xlet when the Xlet is initialized. It provides an Xlet with a mechanism to retrieve properties, as well as a way to signal internal state changes.

See Also:

Xlet

Field Summary

Fields

Modifier and Type	Field and Description
static String	ARGS The property key used to obtain initialization arguments for the Xlet.

Method Summary

Methods

Modifier and Type	Method and Description
ClassLoader	getClassLoader() Returns the base class loader of the Xlet.
Container	getContainer() Get the parent container for an Xlet to put its AWT components in.
Object	getXletProperty(String key) Provides an Xlet with a mechanism to retrieve named properties from the XletContext.
void	notifyDestroyed() Used by an application to notify its manager that it has entered into the Destroyed state.
void	notifyPaused() Notifies the manager that the Xlet does not want to be active and has entered the Paused state.
void	resumeRequest() Provides the Xlet with a mechanism to indicate that it is interested in entering the Active state.

Field Detail

ARGS

static final String ARGS

The property key used to obtain initialization arguments for the Xlet. The call XletContext.getXletProperty(XletContext.ARGS) will return the arguments as an array of Strings. If there are no arguments, then an array of length 0 will be returned.

See Also:

getXletProperty(java.lang.String), Constant Field Values

Method Detail

notifyDestroyed

void notifyDestroyed()

Used by an application to notify its manager that it has entered into the Destroyed state. The application manager will not call the Xlet's destroy method, and all resources held by the Xlet will be considered eligible for reclamation. Before calling this method, the Xlet must have performed the same operations (clean up, releasing of resources etc.) it would have if the Xlet.destroyXlet() had been called.

notifyPaused

void notifyPaused()

Notifies the manager that the Xlet does not want to be active and has entered the Paused state. Invoking this method will have no effect if the Xlet is destroyed, or if it has not yet been started.

If an Xlet calls notifyPaused(), in the future it may receive an Xlet.startXlet() call to request it to become active, or an Xlet.destroyXlet() call to request it to destroy itself.

getXletProperty

Object getXletProperty(String key)

Provides an Xlet with a mechanism to retrieve named properties from the XletContext.

Parameters:

key - The name of the property.

Returns:

A reference to an object representing the property. null is returned if no value is available for key.

Throws:

NullPointerException - If key is null.

IllegalArgumentException - If key is an empty string.

resumeRequest

void resumeRequest()

Provides the Xlet with a mechanism to indicate that it is interested in entering the Active state. Calls to this method can be used by an application manager to determine which Xlets to move to Active state. If the request is fulfilled, the application manager will subsequently call Xlet.startXlet() via a different thread than the one used to call resumeRequest().

See Also:

Xlet.startXlet()

getContainer

Container getContainer()
                       throws UnavailableContainerException

Get the parent container for an Xlet to put its AWT components in. Xlets without a graphical representation need not call this method. If successful, this method returns an instance c of java.awt.Container that is initially invisible, with an arbitrary size and position. Calling c.setVisible(true) will make the container visible.

If this method is called multiple times on the same XletContext instance, the same container will be returned each time. Note that the platform need not support more than a single displayable Xlet at a time, however, at least the first call to this method platform-wide is guaranteed to succeed. The behavior for subsequent calls to this method is implementation-dependent.

The methods for setting the size and position of the xlet's parent container shall attempt to change the shape of the container, but they may fail silently or make platform specific approximations. To discover if a request to change the size or position has succeeded, the Xlet should query the container for the result.

Because the container is initially invisible, an xlet that makes the container visible and that wishes to receive the AWT focus should request this explicitly, i.e. by calling Component.requestFocus().

In order to protect UI elements that are shared between multiple xlets, implementations must prohibit access to resources that belong to a different application context than the calling thread. Therefore, xlets should be aware that an enclosing Container whose getParent() and getFocusCycleRootAncestor() methods return null may not actually be the top of the AWT containment hierarchy.

This method throws UnavailableContainerException If policy or screen real estate does not permit a Container to be granted to the Xlet, or if GraphicsEnvironment.isHeadless() returns true.

Note: Personal Basis Profile permits only a single instance of Frame per GraphicsDevice. In the case of Xlets, this single Frame instance is created in advance by the xlet manager to serve as the parent of the containers returned by this method. Therefore, attempts by an Xlet to create an instance of Frame will always fail.

Returns:

A container with an arbitrary size and position.

Throws:

UnavailableContainerException - If a Container cannot be granted to the Xlet.

See Also:

Component.getParent(), Component.getFocusCycleRootAncestor()

getClassLoader

ClassLoader getClassLoader()

Returns the base class loader of the Xlet. This class loader will be dedicated exclusively to the xlet. All the xlet's classes are loaded by this classloader or by a classloader that has this classloader as its ancestor.