Add a marker to a map

// Copyright 2025 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

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

/// Shows advanced options of markers.
class CustomMarkerSample extends StatefulWidget {
  const CustomMarkerSample({super.key});

  @override
  State<CustomMarkerSample> createState() => _CustomMarkerSampleState();
}

class _CustomMarkerSampleState extends State<CustomMarkerSample> {
  late Marker _marker = Marker(
    markerId: MarkerId('my_marker'),
    // Start with the default Google Maps pin, except yellow.
    // (Note: Hue isn't supported on all platforms.)
    icon: BitmapDescriptor.defaultMarkerWithHue(BitmapDescriptor.hueYellow),
    onTap: _changeIcon,
  );

  @override
  Widget build(BuildContext context) {
    return GoogleMap(
      initialCameraPosition: CameraPosition(target: LatLng(0, 0)),
      markers: {_marker},
    );
  }

  void _changeIcon() async {
    // Set up the image configuration for the new icon, including its size.
    final imageConfiguration = createLocalImageConfiguration(
      context,
      size: Size(42, 52),
    );

    // Load the icon image from an asset.
    // Alternatively, you can create the icon with BitmapDescriptor.bytes(),
    // which allows loading from network or using a CustomPainter.
    final assetIcon = await BitmapDescriptor.asset(
      imageConfiguration,
      'assets/icon_flutter.png',
    );

    setState(() {
      // Modify the existing marker with the new icon and set its anchor
      // to center.
      _marker = _marker.copyWith(
        iconParam: assetIcon,
        anchorParam: const Offset(0.5, 0.5),
      );
    });
  }
}
marker_custom.dart