added from string constructor

lib/model/latlng.dart

@@ -5,6 +5,15 @@ class LatLng {
   LatLng(this.lat, this.lng);
   LatLng.empty() : lat = 0, lng = 0;
 
+  /// must be formatted 'double, double'. For example 35.35217, 89.19659
+  factory LatLng.fromString(String latLng) {
+    final splitString = latLng.split(',');
+    final lat = double.parse(splitString[0].trim());
+    final lng = double.parse(splitString[1].trim());
+
+    return LatLng(lat, lng);
+  }
+
   factory LatLng.fromJson(Map<String, dynamic> json) {
     return LatLng(json['lat'] as double, json['lng'] as double);
   }