How to Add Custom Markers on Google Maps in Flutter?

Google Maps is one of the popular apps used nowadays for navigation or locating markers on Google Maps. We have seen markers on Google Maps for various locations. But In this article, we are going to see how to implement multiple custom markers on Google Maps in Flutter.

Step By Step Implementation

Step 1: Create a New Project in Android Studio

To set up Flutter Development on Android Studio please refer to Android Studio Setup for Flutter Development, and then create a new project in Android Studio please refer to Creating a Simple Application in Flutter.

Step 2: Generating API Key for Using Google Maps

Check out the below article on How to generate an API key for using Google Maps. After developing that key we have to use it within our project to integrate Google Maps. 

Now, follow the Steps to Implement Google Maps in the Flutter Application

Step 3: Adding Dependency to pubspec.yaml File

dependencies:
    flutter: 
    google_maps_flutter: ^2.1.8

Now click on pub.get to configure.

Step 4: Update build.gradle File

Navigate to android>app>build.gradle file and update code on below line. 

Change Compile SDK Version

android {
    compileSdkVersion 31

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

Change Min SDK Version

defaultConfig {
    // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
    applicationId "com.example.google_maps"
    minSdkVersion 20
    targetSdkVersion 30
    versionCode flutterVersionCode.toInteger()
    versionName flutterVersionName
}

Step 5: Add API Key to Android Manifest File

Navigate to android > app > src > main > AndrodManifest.xml file and add the below code in the manifest tag. Make sure to add your Google Maps API key in the value. 

<meta-data android:name="com.google.android.geo.API_KEY"
        android:value="Enter your API key here"/>

Step 6: Add Images in pubspec.yaml File for displaying Custom Markers

Add images in the assets folder in pubspec.yaml file

# To add assets to your application, add an assets section, like this
assets:
    - images/bus.png
    - images/car.png
    - images/travelling.png
    - images/bycicle.png
    - images/food-delivery.png

Step 7: Working with main.dart File

Navigate to lib > main.dart file and add the below code to it. Comments are added in the code to get to know in detail. 

Dart

import 'package:flutter/material.dart';
import 'package:google_maps/Convert_Lat_Long.dart';
import 'package:google_maps/HomePage.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'GFG',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      // First screen of our app
      home: const HomePage(),
    );
  }
}

Step 8: Creating a new Dart File for Home Page

Navigate to lib > Right click on it > New > Dart File and name it as HomePage.dart. After creating that file add the below code to it. Comments are added in the code to get to know in detail.

Dart

import 'dart:async';
import 'dart:typed_data';
import 'dart:ui' as ui;
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:geolocator/geolocator.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {

  // created controller for displaying Google Maps
  Completer<GoogleMapController> _controller = Completer();

  // given camera position
  static final CameraPosition _kGoogle = const CameraPosition(
      target: LatLng(19.0759837, 72.8776559),
    zoom: 15,
  );

  Uint8List? marketimages;
  List<String> images = ['images/car.png','images/bus.png', 'images/travelling.png', 'images/bycicle.png', 'images/food-delivery.png'];

  // created empty list of markers
  final List<Marker> _markers = <Marker>[];

  // created list of coordinates of various locations
  final List<LatLng> _latLen = <LatLng>[

    LatLng(19.0759837, 72.8776559),
    LatLng(28.679079, 77.069710),
    LatLng(26.850000, 80.949997),
    LatLng(24.879999, 74.629997),
    LatLng(16.166700, 74.833298),
    LatLng(12.971599, 77.594563),
  ];

  // declared method to get Images
  Future<Uint8List> getImages(String path, int width) async{
    ByteData data = await rootBundle.load(path);
    ui.Codec codec = await ui.instantiateImageCodec(data.buffer.asUint8List(), targetHeight: width);
    ui.FrameInfo fi = await codec.getNextFrame();
    return(await fi.image.toByteData(format: ui.ImageByteFormat.png))!.buffer.asUint8List();

  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    // initialize loadData method
    loadData();
  }

  // created method for displaying custom markers according to index
  loadData() async{
    for(int i=0 ;i<images.length; i++){
      final Uint8List markIcons = await getImages(images[i], 100);
      // makers added according to index
      _markers.add(
        Marker(
          // given marker id
          markerId: MarkerId(i.toString()),
          // given marker icon
          icon: BitmapDescriptor.fromBytes(markIcons),
          // given position
          position: _latLen[i],
          infoWindow: InfoWindow(
            // given title for marker
            title: 'Location: '+i.toString(),
          ),
        )
      );
      setState(() {
      });
    }
  }

 @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Color(0xFF0F9D58),
        // on below line we have given title of app
        title: Text("GFG"),
      ),
      body: Container(
        child: SafeArea(
          child: GoogleMap(
            // given camera position
              initialCameraPosition: _kGoogle,
            // set markers on google map
            markers: Set<Marker>.of(_markers),
            // on below line we have given map type
            mapType: MapType.normal,
            // on below line we have enabled location
            myLocationEnabled: true,
            myLocationButtonEnabled: true,
            // on below line we have enabled compass
            compassEnabled: true,
            // below line displays google map in our app
            onMapCreated: (GoogleMapController controller){
                _controller.complete(controller);
            },
          ),
        ),
      ),
    );
  }
}

Output: