Method Channel in Flutter | Full Explanation With Examples

Method Channel in Flutter in Flutter is used to communicate with platform-specific code. You can use the native languages (Java/Kotlin for Android and Objective-C/Swift for iOS). This allows you to access platform-specific features, such as getting the device’s location. Here’s a complete example of how to use the Method Channel to get the device’s location:

Steps to use Method Channel in Flutter

Set up the Flutter project: Create a new Flutter project or use an existing one.
Add the required dependencies: In your pubspec.yaml file, or add the following dependencies:

We will fetch the location of the device using method channel so for that we can have the “geolocator” depedency. fluttertoast is used to show the toast.


dependencies:
  flutter:
    sdk: flutter

  # Add these dependencies for location services and method channel
  geolocator: ^7.6.2
  fluttertoast: ^8.0.8

Then, run > “flutter pub get" to install the new dependencies.

Implement the Flutter Code


import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:geolocator/geolocator.dart';
import 'package:fluttertoast/fluttertoast.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: LocationScreen(),
    );
  }
}

class LocationScreen extends StatefulWidget {
  @override
  _LocationScreenState createState() => _LocationScreenState();
}

class _LocationScreenState extends State<LocationScreen> {
  static const platformChannel = MethodChannel('your_channel_name_here');

  String _locationText = 'Press the button to get location';

  Future<void> _getLocation() async {
    try {
      final result = await platformChannel.invokeMethod('getLocation');
      setState(() {
        _locationText = 'Location: $result';
      });
    } on PlatformException catch (e) {
      Fluttertoast.showToast(msg: "Error: ${e.message}");
      setState(() {
        _locationText = "Error getting location";
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Location Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              _locationText,
              style: TextStyle(fontSize: 18),
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _getLocation,
              child: Text('Get Location'),
            ),
          ],
        ),
      ),
    );
  }
}

Implement platform-specific code (Android/iOS):

Now, you need to implement platform-specific code for getting the device’s location. For the sake of this example, we will provide the code for Android only.

In your Android project, navigate to android/app/src/main/java/com/example/your_app_name_here/ and create a new Java file (if not already created) named MainActivity.java. Then, add the following code:

For Android:


package com.example.your_app_name_here;

import android.os.Bundle;
import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugins.GeneratedPluginRegistrant;
import android.location.Location;
import android.location.LocationManager;
import android.os.Build;
import android.content.Context;

public class MainActivity extends FlutterActivity {
    private static final String CHANNEL = "your_channel_name_here";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        GeneratedPluginRegistrant.registerWith(this);
    }

    @Override
    public void configureFlutterEngine(FlutterEngine flutterEngine) {
        super.configureFlutterEngine(flutterEngine);

        new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
                .setMethodCallHandler((call, result) -> {
                    if (call.method.equals("getLocation")) {
                        try {
                            LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
                            Location lastKnownLocation = null;
                            if (locationManager != null) {
                                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
                                    if (checkSelfPermission(android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
                                        lastKnownLocation = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                                    }
                                } else {
                                    lastKnownLocation = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                                }
                            }

                            if (lastKnownLocation != null) {
                                double latitude = lastKnownLocation.getLatitude();
                                double longitude = lastKnownLocation.getLongitude();
                                result.success("Latitude: " + latitude + ", Longitude: " + longitude);
                            } else {
                                result.error("LOCATION_UNAVAILABLE", "Location data is not available.", null);
                            }
                        } catch (Exception e) {
                            result.error("ERROR", e.getMessage(), null);
                        }
                    } else {
                        result.notImplemented();
                    }
                });
    }
}

For IOS:

In your AppDelegate.swift file (located at ios/Runner/), update the application(_:didFinishLaunchingWithOptions:) method to implement the location retrieval functionality and communicate with Flutter using the MethodChannel. Here’s how:


import UIKit
import Flutter
import CoreLocation

@UIApplicationMain
class AppDelegate: FlutterAppDelegate {
    override func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        let controller: FlutterViewController = window?.rootViewController as! FlutterViewController

        // Register the MethodChannel
        let channel = FlutterMethodChannel(name: "your_channel_name_here", binaryMessenger: controller.binaryMessenger)
        channel.setMethodCallHandler { [weak self] call, result in
            if call.method == "getLocation" {
                self?.getLocation(result: result)
            } else {
                result(FlutterMethodNotImplemented)
            }
        }

        GeneratedPluginRegistrant.register(with: self)
        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
    }

    func getLocation(result: @escaping FlutterResult) {
        let locationManager = CLLocationManager()
        locationManager.delegate = self
        locationManager.requestWhenInUseAuthorization()

        if CLLocationManager.locationServicesEnabled() {
            locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters
            locationManager.startUpdatingLocation()
            // Note: You can use the `CLLocationManager` delegate methods to handle the location updates.
            // For simplicity, we'll use the last known location in this example.
            if let location = locationManager.location {
                let latitude = location.coordinate.latitude
                let longitude = location.coordinate.longitude
                result("Latitude: \(latitude), Longitude: \(longitude)")
            } else {
                result("Location data is not available.")
            }
        } else {
            result("Location services are not enabled.")
        }
    }
}

Now run the app to test your application.