onCall property
An event channel for monitoring sensor events.
Stream<CallsData>
allow us to monitor the sensor update
events as follows:
sensor.onCall.listen((data) {
print(data)
}
[Creating Streams](https://www.dartlang.org/articles/libraries/creating-streams)
Implementation
Stream<CallsData> get onCall {
onCallStreamController.close();
onCallStreamController = StreamController<CallsData>();
return onCallStreamController.stream;
}