4⃣
Controller
The
mapController property takes a MapController, and whilst it is optional, it is strongly recommended for any map other than the most basic. It allows you to programmatically interact with the map, such as panning, zooming and rotating.To use a
MapController, it must initialised and then passed to the FlutterMap. This attaches them until the widget is destroyed/disposed.final mapController = MapController();
@override
Widget build(BuildContext context) =>
FlutterMap(
mapController: mapController,
...
);
It is a fairly common requirement to need to use the
MapController before the map has been built, or to initialise a listener for one of it's streams inside the initState() StatefulWidget method. Unfortunately, this is not possible, as the map must be built for the controller to be attached.Luckily, Flutter provides methods to wait until the first frame has been built, which usually means the
FlutterMap widget will have been built (see exception circumstances below). This makes it trivially easy to implement the desired behaviour.Recommended Usage
@override
void initState(){
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) {
// Use `MapController` as needed
});
}
For simplicity and readability, it is not recommended to use this method unless needed in your situation, although there should be little technical difference.
In some cases, the
FlutterMap widget may not have been built on the first frame - for example when using a FutureBuilder around the map.In this case, an alternative method is required to use the
MapController on build. This method uses the When Map Ready (onMapReady) callback.Alternative Usage
@override
Widget build(BuildContext context) =>
FlutterMap(
mapController: mapController,
options: MapOptions(
onMapReady: () {
// Use `MapController` as needed
},
),
);
MapController class - flutter_map library - Dart API
Full API Reference
Last modified 2mo ago