onTap property Null safety

VoidCallback? onTap
final

Callback to receive tap event for this circle.

You can customize the appearance of the tapped circle based on the index passed on it as shown in the below code snippet.

 late List<MapLatLng> _circles;
 late MapShapeSource _mapSource;
 int _selectedIndex = -1;

 @override
 void initState() {
   _circles = const <MapLatLng>[
     MapLatLng(-14.235004, -51.92528),
     MapLatLng(51.16569, 10.451526),
     MapLatLng(-25.274398, 133.775136),
     MapLatLng(20.593684, 78.96288),
     MapLatLng(61.52401, 105.318756)
   ];

   _mapSource = MapShapeSource.asset(
     'assets/world_map.json',
     shapeDataField: 'name',
   );
   super.initState();
 }

 @override
 Widget build(BuildContext context) {
   return Scaffold(
     body: Center(
         child: Container(
       height: 350,
       child: Padding(
         padding: EdgeInsets.only(left: 15, right: 15),
         child: SfMaps(
           layers: <MapLayer>[
             MapShapeLayer(
               source: _mapSource,
               sublayers: [
                 MapCircleLayer(
                   circles: List<MapCircle>.generate(
                     _circles.length,
                     (int index) {
                       return MapCircle(
                         center: _circles[index],
                         color: _selectedIndex == index
                           ? Colors.blue
                           : Colors.red,
                         onTap: () {
                           setState(() {
                            _selectedIndex = index;
                         });
                       });
                     },
                   ).toSet(),
                 ),
               ],
             ),
           ],
         ),
       ),
     )),
   );
 }

Implementation

final VoidCallback? onTap;