Summary - Location

Combine getLocation and onLocationChanged to make a map view.

Map application

A map application combines getLocation and onLocationChanged. On launch, getLocation reads the initial position and centers the map there. Then the onLocationChanged stream is listened to so the map updates as the device moves.

final initial = await location.getLocation();
print(initial.latitude);
location.onLocationChanged.listen((data) {
  print(data.latitude);
});

Exercise Write a map flow

Create a Location instance. First await the initial position with getLocation and print its latitude. Then listen to the onLocationChanged stream and print the incoming latitude. Wait 10 milliseconds.

Show example solution

class LocationData {
  final double latitude;
  LocationData(this.latitude);
}

class Location {
  Future<LocationData> getLocation() async => LocationData(41.0);
  Stream<LocationData> get onLocationChanged => Stream.value(LocationData(41.5));
}

void main() async {
  final location = Location();
  final initial = await location.getLocation();
  print(initial.latitude);
  location.onLocationChanged.listen((data) {
    print(data.latitude);
  });
  await Future.delayed(Duration(milliseconds: 10));
}

Test yourself

How are getLocation and onLocationChanged used together in a map application?
- onLocationChanged replaces getLocation
- Both cannot be called at the same time
- Only getLocation is used, the stream is ignored
- getLocation gives the initial position, onLocationChanged tracks movement
Show answer

getLocation gives the initial position, onLocationChanged tracks movement — getLocation reads the initial position once, while onLocationChanged emits continuously as the device moves; they are used together.

Get the initial position

final initial = await location.____;

Show answer

final initial = await location.getLocation();

Map parts

getLocation

Initial position
onLocationChanged

Continuous tracking
LocationData

Location data
listen

Listens to the stream

Next lesson: What is workmanager?

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies