React Native vs. Flutter 2026: Welches Framework sollten Sie wählen?

// App.tsx
import React, { useState } from 'react';
import {
  View, Text, TextInput, FlatList, TouchableOpacity,
  StyleSheet, StatusBar
} from 'react-native';
import { SafeAreaView } from 'react-native-safe-area-context';

interface TodoItem {
  id: string;
  text: string;
  completed: boolean;
}

export default function App() {
  const [todos, setTodos] = useState<TodoItem[]>([]);
  const [input, setInput] = useState('');

  const addTodo = () => {
    if (!input.trim()) return;
    setTodos(prev => [...prev, { id: Date.now().toString(), text: input, completed: false }]);
    setInput('');
  };

  const toggleTodo = (id: string) => {
    setTodos(prev => prev.map(t => t.id === id ? { ...t, completed: !t.completed } : t));
  };

  return (
    <SafeAreaView style={styles.container}>
      <StatusBar barStyle="dark-content" />
      <Text style={styles.title}>Todo App</Text>
      <View style={styles.inputRow}>
        <TextInput
          style={styles.input}
          value={input}
          onChangeText={setInput}
          placeholder="Add a task..."
          onSubmitEditing={addTodo}
        />
        <TouchableOpacity style={styles.button} onPress={addTodo}>
          <Text style={styles.buttonText}>Add</Text>
        </TouchableOpacity>
      </View>
      <FlatList
        data={todos}
        keyExtractor={item => item.id}
        renderItem={({ item }) => (
          <TouchableOpacity onPress={() => toggleTodo(item.id)}>
            <Text style={[styles.todo, item.completed && styles.done]}>
              {item.completed ? '✓ ' : '○ '}{item.text}
            </Text>
          </TouchableOpacity>
        )}
      />
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: { flex: 1, padding: 16, backgroundColor: '#fff' },
  title: { fontSize: 28, fontWeight: 'bold', marginBottom: 16 },
  inputRow: { flexDirection: 'row', gap: 8, marginBottom: 16 },
  input: { flex: 1, borderWidth: 1, borderColor: '#ddd', borderRadius: 8, padding: 12 },
  button: { backgroundColor: '#007AFF', borderRadius: 8, padding: 12, justifyContent: 'center' },
  buttonText: { color: '#fff', fontWeight: '600' },
  todo: { fontSize: 16, padding: 12, borderBottomWidth: 1, borderBottomColor: '#f0f0f0' },
  done: { textDecorationLine: 'line-through', color: '#999' },
});

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

void main() => runApp(const TodoApp());

class TodoApp extends StatelessWidget {
  const TodoApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Todo App',
      theme: ThemeData(useMaterial3: true, colorSchemeSeed: Colors.blue),
      home: const TodoScreen(),
    );
  }
}

class TodoItem {
  final String id;
  final String text;
  bool completed;
  TodoItem({required this.id, required this.text, this.completed = false});
}

class TodoScreen extends StatefulWidget {
  const TodoScreen({super.key});
  @override
  State<TodoScreen> createState() => _TodoScreenState();
}

class _TodoScreenState extends State<TodoScreen> {
  final List<TodoItem> _todos = [];
  final _controller = TextEditingController();

  void _addTodo() {
    if (_controller.text.isEmpty) return;
    setState(() {
      _todos.add(TodoItem(id: DateTime.now().toString(), text: _controller.text));
    });
    _controller.clear();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Todo App'), centerTitle: true),
      body: Column(children: [
        Padding(
          padding: const EdgeInsets.all(16),
          child: Row(children: [
            Expanded(
              child: TextField(
                controller: _controller,
                decoration: const InputDecoration(
                  hintText: 'Add a task...',
                  border: OutlineInputBorder(),
                ),
                onSubmitted: (_) => _addTodo(),
              ),
            ),
            const SizedBox(width: 8),
            FilledButton(onPressed: _addTodo, child: const Text('Add')),
          ]),
        ),
        Expanded(
          child: ListView.builder(
            itemCount: _todos.length,
            itemBuilder: (context, index) {
              final todo = _todos[index];
              return ListTile(
                leading: Checkbox(
                  value: todo.completed,
                  onChanged: (_) => setState(() => todo.completed = !todo.completed),
                ),
                title: Text(todo.text,
                  style: TextStyle(decoration: todo.completed ? TextDecoration.lineThrough : null)),
              );
            },
          ),
        ),
      ]),
    );
  }
}