In Web Dynpro, the UI elements are defined as interfaces. All independent elements are derived from the abstract base class IWDUIElement, whereas the aggregated elements are derived from the abstract base class IWDViewElement.
BarCodeReader, FunctionKey and RFIDReader only can be used with Pocket PCs, for documentation on these UI elements, refer to Developing Mobile Always Connected Applications.
For documentation on interactive Adobe forms, refer to Development of Interactive Adobe Forms for the Web Dynpro UI.
JavaDocs: http://help.sap.com/javadocs