Java Reference
In-Depth Information
An Xlet has an accompanying
XletContext
object, which gives the Xlet access to criti-
cal information about the application management environment, including the class
loader used by the Xlet, the root container into which it should place its GUI elements,
and runtime properties. An Xlet can also access any launch arguments provided by the
application management system as a property of the
XletContext
.
Multiple Xlets can run at one time; the application manager partitions the screen
into separate containers, giving a root container to each Xlet. Unlike the MIDP, which
defines a user-interface hierarchy, the PBP requires only the presence of lightweight AWT
components that an Xlet and its supporting classes may override to create a user inter-
face. This can pose challenges for cross-platform Xlets, because different Java ME devices
supporting the CDC may have different user interfaces, spanning the gamut from custom
GUIs based on the lightweight AWT hierarchy to the AGUI implementing much of Java
Swing, to other Java packages such as those that provide SVG and 3D graphics.
Xlets can share data through an interface based on the Java RMI; the runtime for
PBP-enabled devices includes a system-wide registry for remoted objects that implement
the
java.rmi.Remote
interface. Using this interface, you can write classes that implement
objects that share data through methods, or you can offload computational tasks to
another running Xlet.
