The SDK is composed of several key classes illustrated in the image below.
The class Voice is the entry point into the SDK and does the following:
The class Call represents an outgoing or incoming call.
The class CallInvite represents an invitation to an incoming call. You can accept or reject the call invitation using this class.
The class CancelledCallInvite represents an invitation to a call that has been subsequently cancelled. A call can be cancelled for several reasons and this is detailed further in the documentation for Voice.handleMessage(...)