Flutter and iOS Swift: How to Interact and Add Platform-Specific Code

Flutter is a powerful framework for building cross-platform mobile apps with a single codebase. However, there may be times when you need to add platform-specific code to your app to access features that are not available in Flutter. In this blog post, we will show you how to add platform-specific code to a Flutter app to detect system uptime on iOS.

Prerequisites

Before we begin, make sure you have the following installed:

• Flutter SDK
• Xcode (for iOS development)

Creating the Method Channel

To add platform-specific code to a Flutter app, we need to create a method channel that connects the Flutter code to the native code. In this case, we will create a method channel named my_channel that will be used to call a method that returns the system uptime on iOS.

In AppDelegate.swift, add the following code to create the method channel:

import UIKit
import Flutter

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
  var window: UIWindow?

  func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    let controller = window?.rootViewController as! FlutterViewController
    let channel = FlutterMethodChannel(name: "my_channel", binaryMessenger: controller.binaryMessenger)
    channel.setMethodCallHandler { (call, result) in
      if call.method == "getSystemUptime" {
        let uptime = ProcessInfo.processInfo.systemUptime
        result(uptime)
      } else {
        result(FlutterMethodNotImplemented)
      }
    }

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

This code creates a new method channel named my_channel and adds a handler for the getSystemUptime method. When this method is called from Flutter, it returns the system uptime using ProcessInfo.processInfo.systemUptime.

Creating the Flutter Class

Next, we will create a new Flutter class named SystemUptime that connects to AppDelegate.swift and returns the system uptime using the getSystemUptime method.

In system_uptime.dart, add the following code:

import 'package:flutter/services.dart';

class SystemUptime {
  static const platform = const MethodChannel('my_channel');

  static Future<double> getUptime() async {
    try {
      final double uptime = await platform.invokeMethod('getSystemUptime');
      return uptime;
    } on PlatformException catch (e) {
      print("Failed to get system uptime: ${e.message}");
      return 0.0;
    }
  }
}

This code creates a new class named SystemUptime that connects to AppDelegate.swift using a method channel named my_channel. The getUptime method calls the getSystemUptime method in AppDelegate.swift and returns the system uptime.

Using the Flutter Class

Finally, we will use the SystemUptime class in our Flutter code to display the system uptime in the app.

In main.dart, add the following code:

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

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  double _uptime = 0.0;

  @override
  void initState() {
    super.initState();
    _getSystemUptime();
  }

  Future<void> _getSystemUptime() async {
    final uptime = await SystemUptime.getUptime();
    setState(() {
      _uptime = uptime;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('System Uptime'),
        ),
        body: Center(
          child: Text('System uptime: $_uptime seconds'),
        ),
      ),
    );
  }
}

This code creates a new Flutter app that displays the system uptime in the app. The initState method calls the _getSystemUptime method to get the system uptime using the SystemUptime class. The build method displays the system uptime in the app.

Conclusion

In this blog post, we showed you how to add platform-specific code to a Flutter app to detect system uptime on iOS. We created a method channel in AppDelegate.swift, a Flutter class in system_uptime.dart, and used the class in main.dart to display the system uptime in the app. With this knowledge, you can now add platform-specific code to your Flutter app to access features that are not available in Flutter.