flutter_maps_demo/lib/main.dart

import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

void main() {
  runApp(MaterialApp(
    home: new Scaffold(
      appBar: AppBar(title: const Text('Google Maps demo')),
      body: MapsDemo(),
    ),
  ));
}

class MapsDemo extends StatefulWidget {
  @override
  State createState() => MapsDemoState();
}

class MapsDemoState extends State<MapsDemo> {

  GoogleMapController mapController;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.all(15.0),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: <Widget>[
          Center(
            child: SizedBox(
              width: 300.0,
              height: 200.0,
              child: GoogleMap(
                options: GoogleMapOptions(
                  mapType: MapType.hybrid,
                ),
                onMapCreated: _onMapCreated,
              ),
            ),
          ),
          RaisedButton(
            child: const Text('Go to London'),
            onPressed: mapController == null ? null : () {
              mapController.animateCamera(CameraUpdate.newCameraPosition(
                const CameraPosition(
                  bearing: 270.0,
                  target: LatLng(51.5160895, -0.1294527),
                  tilt: 30.0,
                  zoom: 17.0,
                ),
              ));
              mapController.addMarker(MarkerOptions(
                position: LatLng(51.5160895, -0.1294527),
                infoWindowText: InfoWindowText('London', 'Eine schöne Stadt')
              ));
            },
          ),
        ],
      ),
    );
  }

  void _onMapCreated(GoogleMapController controller) {
    setState(() { mapController = controller; });
  }
}