Android listens to telephoney

* Registers a listener object to receive notification of changes * in specified telephony states. * to register a listener, pass a {@ link phonestatelistener} * and specify at least one telephony state of interest in * The events argument. * At registration, and when a specified telephony state * changes, the Telephony Manager invokes the appropriate * callback method on the listener object and passes the * Current (udpated) values. * To unregister a listener, pass the listener object and set the * Events argument to {@ link phonestatelistener # listen_none} (0) telmanager = (telephonymanager) getsystemservice (context. telephony_service); pslistener = new phonestatuslistener (); telmanager. listen (pslistener, phonestatelistener. listen_call_state); // listens to telmanager. listen (pslistener, phonestatelistener. listen_none); // cancel the listener