Kotlin Multiplatform vs. React Native vs. Flutter: Building Your First App

Choosing the right framework for your first cross-platform app can be challenging, especially with so many great options available. To help you decide, let’s compare Kotlin Multiplatform (KMP), React Native, and Flutter by building a simple “Hello World” app with each framework. We’ll also evaluate them across key aspects like setup, UI development, code sharing, performance, community, and developer experience. By the end, you’ll have a clear understanding of which framework is best suited for your first app.

Building a “Hello World” App

1. Kotlin Multiplatform (KMP)

Kotlin Multiplatform allows you to share business logic across platforms while using native UI components. Here’s how to build a “Hello World” app:

Steps:

1. Set Up the Project:
   • Install Android Studio and the Kotlin Multiplatform Mobile plugin.
   • Create a new KMP project using the “Mobile Library” template.
2. Shared Code:In the shared module, create a Greeting class with a function to return “Hello World”.

   // shared/src/commonMain/kotlin/Greeting.kt
   class Greeting {
       fun greet(): String {
           return "Hello, World!"
       }
   }

3. Platform-Specific UIs:For Android, use Jetpack Compose or XML layouts in the androidApp module. For iOS, use SwiftUI or UIKit in the iosApp module.Android (Jetpack Compose):

   // androidApp/src/main/java/com/example/androidApp/MainActivity.kt
   class MainActivity : ComponentActivity() {
       override fun onCreate(savedInstanceState: Bundle?) {
           super.onCreate(savedInstanceState)
           setContent {
               Text(text = Greeting().greet())
           }
       }
   }

   iOS (SwiftUI):

   // iosApp/iosApp/ContentView.swift
   struct ContentView: View {
       var body: some View {
           Text(Greeting().greet())
       }
   }

4. Run the App:Build and run the app on Android and iOS simulators/emulators.

Pros and Cons:

2. React Native

React Native allows you to build cross-platform apps using JavaScript and React. Here’s how to build a “Hello World” app:

Steps:

1. Set Up the Project:
   • Install Node.js and the React Native CLI.
   • Create a new project:

     npx react-native init HelloWorldApp

2. Write the Code:Open App.js and replace the content with the following:

   import React from 'react';
   import { Text, View } from 'react-native';
   
   const App = () => {
       return (
           <View style={{ flex: 1, justifyContent: 'center', alignItems: 'center' }}>
               <Text>Hello, World!</Text>
           </View>
       );
   };
   
   export default App;

3. Run the App:Start the Metro bundler:

   npx react-native start

   Run the app on Android or iOS:

   npx react-native run-android
   npx react-native run-ios

Pros and Cons:

3. Flutter

Flutter is a UI toolkit for building natively compiled apps for mobile, web, and desktop using Dart. Here’s how to build a “Hello World” app:

Steps:

1. Set Up the Project:
   • Install Flutter SDK and Android Studio/VS Code.
   • Create a new project:

     flutter create hello_world_app

2. Write the Code:Open lib/main.dart and replace the content with the following:

   import 'package:flutter/material.dart';
   
   void main() {
       runApp(MyApp());
   }
   
   class MyApp extends StatelessWidget {
       @override
       Widget build(BuildContext context) {
           return MaterialApp(
               home: Scaffold(
                   appBar: AppBar(title: Text('Hello World App')),
                   body: Center(child: Text('Hello, World!')),
               ),
           );
       }
   }

3. Run the App:Run the app on Android or iOS:

   flutter run

Pros and Cons:

Comparing the Frameworks

1. Initial Setup

• KMP: Moderate setup complexity, especially for iOS. Requires configuring Gradle files and platform-specific dependencies.
• React Native: Easy setup with tools like Expo and React Native CLI.
• Flutter: Smoothest setup with the Flutter CLI and flutter doctor command.

Best option: Flutter (for ease of initial setup).

2. UI Development

• KMP: Platform-specific UIs (Jetpack Compose for Android, SwiftUI/UIKit for iOS). Offers native flexibility but requires separate UI code.
• React Native: Declarative UI with JSX. Powerful but can feel like a middle ground between native and custom rendering.
• Flutter: Widget-based system for consistent cross-platform UIs. Highly customizable but requires learning Dart.

Best option: A tie between KMP (for native UI flexibility) and Flutter (for cross-platform consistency).

3. Code Sharing

• KMP: Excels at sharing business logic while allowing native UIs.
• React Native: High code sharing but may require platform-specific code for advanced features.
• Flutter: High code sharing for both UI and business logic but requires Dart.

Best option: Kotlin Multiplatform (for its focus on sharing business logic).

4. Performance

• KMP: Native performance due to native UIs and compiled shared code.
• React Native: Good performance but can struggle with complex UIs due to the JavaScript bridge.
• Flutter: Excellent performance, often close to native, but may not match native performance in all scenarios.

Winner: Kotlin Multiplatform (for native performance).

5. Community and Ecosystem

• KMP: Growing community backed by JetBrains. Kotlin ecosystem is mature.
• React Native: Large and active community with a rich ecosystem.
• Flutter: Thriving community with strong Google support.

Best option: React Native (for its large and mature community), but Flutter is a close contender.

6. Developer Experience

• KMP: Gentle learning curve for Kotlin developers but requires platform-specific UI knowledge.
• React Native: Familiar for JavaScript/React developers but may require native mobile knowledge.
• Flutter: Excellent developer experience with hot reload and comprehensive documentation.

Best option: Flutter (for its excellent developer experience and tooling).

7. AI-Assisted Development Speed

With the rise of AI tools like GitHub Copilot, ChatGPT, Gemini, Claude, etc.. Developers can significantly speed up app development. Let’s evaluate how each framework benefits from AI assistance:

• KMP: AI tools can help generate Kotlin code for shared logic and even platform-specific UIs. However, the need for platform-specific knowledge may limit the speed gains.
• React Native: JavaScript is widely supported by AI tools, making it easy to generate boilerplate code, components, and even entire screens. The large ecosystem also means AI can suggest relevant libraries and solutions.
• Flutter: Dart is less commonly supported by AI tools compared to JavaScript, but Flutter’s widget-based system is highly structured, making it easier for AI to generate consistent and functional code.

Best option: React Native (due to JavaScript’s widespread support in AI tools).

The resolution:

There’s no one-size-fits-all answer. The best choice depends on your priorities:

• • Prioritize Performance and Native UI: Choose Kotlin Multiplatform.
  • Prioritize Speed of Development and a Large Community: Choose React Native.
  • Prioritize Ease of Use, Cross-Platform Consistency, and Fast Development: Choose Flutter.

For Your First App:

• Simple App, Fast Development: Flutter is an excellent choice. Its ease of setup, hot reload, and comprehensive widget system will get you up and running quickly.
• Existing Kotlin/Android Skills, Focus on Shared Logic: Kotlin Multiplatform allows you to leverage your existing knowledge while sharing a significant portion of your codebase.
• Web Developer, Familiar with React: React Native is a natural fit, allowing you to utilize your web development skills for mobile development.

Conclusion

Each framework has its strengths and weaknesses, and the best choice depends on your team’s expertise, project requirements, and long-term goals. For your first app, consider starting with Flutter for its ease of use and fast development, React Native if you’re a web developer, or Kotlin Multiplatform if you’re focused on performance and native UIs.

Try building a simple app with each framework to see which one aligns best with your preferences and project requirements.

References

 

Source: Read More