React Native 0.86 im Jahr 2026: Edge-to-Edge Android, DevTools und Interviewfragen

import React, { useRef, useCallback } from 'react';
import { View, TouchableOpacity, Text, StyleSheet } from 'react-native';
import { useSafeAreaInsets } from 'react-native-safe-area-context';

interface TooltipPosition {
  x: number;
  y: number;
}

export function SafeAreaHandler() {
  const buttonRef = useRef<View>(null);
  const insets = useSafeAreaInsets();

  const showTooltip = useCallback(() => {
    // measureInWindow now returns correct coordinates on Android 15+
    buttonRef.current?.measureInWindow((x, y, width, height) => {
      const position: TooltipPosition = {
        x: x + width / 2,
        // Coordinates are accurate even with edge-to-edge enabled
        y: y + height + 8,
      };
      console.log('Tooltip position:', position);
    });
  }, []);

  return (
    <View style={[styles.container, { paddingTop: insets.top }]}>
      <View ref={buttonRef} collapsable={false}>
        <TouchableOpacity onPress={showTooltip} style={styles.button}>
          <Text style={styles.buttonText}>Show Tooltip</Text>
        </TouchableOpacity>
      </View>
    </View>
  );
}

const styles = StyleSheet.create({
  container: { flex: 1, alignItems: 'center', justifyContent: 'center' },
  button: { backgroundColor: '#007AFF', padding: 16, borderRadius: 8 },
  buttonText: { color: '#FFFFFF', fontWeight: '600' },
});

import React, { useState } from 'react';
import {
  KeyboardAvoidingView,
  TextInput,
  Platform,
  StyleSheet,
  View,
} from 'react-native';
import { useSafeAreaInsets } from 'react-native-safe-area-context';

export function ChatInput() {
  const [message, setMessage] = useState('');
  const insets = useSafeAreaInsets();

  return (
    <KeyboardAvoidingView
      // behavior="padding" works correctly on Android 15+ edge-to-edge
      behavior={Platform.OS === 'ios' ? 'padding' : 'padding'}
      style={styles.container}
      // keyboardVerticalOffset accounts for headers and safe areas
      keyboardVerticalOffset={Platform.select({ ios: 88, android: 0 })}
    >
      <View style={styles.content}>
        {/* Chat messages would render here */}
      </View>
      <View style={[styles.inputContainer, { paddingBottom: insets.bottom }]}>
        <TextInput
          value={message}
          onChangeText={setMessage}
          placeholder="Type a message..."
          style={styles.input}
          multiline
        />
      </View>
    </KeyboardAvoidingView>
  );
}

const styles = StyleSheet.create({
  container: { flex: 1 },
  content: { flex: 1 },
  inputContainer: { borderTopWidth: 1, borderTopColor: '#E5E5E5', padding: 8 },
  input: { minHeight: 40, padding: 12, backgroundColor: '#F5F5F5', borderRadius: 20 },
});

import React, { useState, useEffect } from 'react';
import { Modal, View, StatusBar, Text, Pressable, StyleSheet } from 'react-native';

interface ThemedModalProps {
  visible: boolean;
  onClose: () => void;
  darkMode?: boolean;
}

export function ThemedModal({ visible, onClose, darkMode = false }: ThemedModalProps) {
  // StatusBar changes now apply correctly while modal is visible
  useEffect(() => {
    if (visible) {
      StatusBar.setBarStyle(darkMode ? 'light-content' : 'dark-content', true);
      StatusBar.setBackgroundColor(darkMode ? '#1A1A1A' : '#FFFFFF', true);
    }
    return () => {
      // Restore original status bar when modal closes
      StatusBar.setBarStyle('dark-content', true);
      StatusBar.setBackgroundColor('#FFFFFF', true);
    };
  }, [visible, darkMode]);

  return (
    <Modal visible={visible} animationType="slide" onRequestClose={onClose}>
      <View style={[styles.modalContent, darkMode && styles.darkBackground]}>
        <StatusBar
          barStyle={darkMode ? 'light-content' : 'dark-content'}
          backgroundColor={darkMode ? '#1A1A1A' : '#FFFFFF'}
        />
        <Text style={[styles.title, darkMode && styles.lightText]}>
          Modal Content
        </Text>
        <Pressable onPress={onClose} style={styles.closeButton}>
          <Text style={styles.closeButtonText}>Close</Text>
        </Pressable>
      </View>
    </Modal>
  );
}

const styles = StyleSheet.create({
  modalContent: { flex: 1, justifyContent: 'center', alignItems: 'center', backgroundColor: '#FFFFFF' },
  darkBackground: { backgroundColor: '#1A1A1A' },
  title: { fontSize: 24, fontWeight: 'bold', color: '#000000' },
  lightText: { color: '#FFFFFF' },
  closeButton: { marginTop: 20, padding: 12, backgroundColor: '#007AFF', borderRadius: 8 },
  closeButtonText: { color: '#FFFFFF', fontWeight: '600' },
});

import React, { createContext, useContext, useState, useEffect } from 'react';
import { useColorScheme, Appearance } from 'react-native';

type Theme = 'light' | 'dark';

interface ThemeContextValue {
  theme: Theme;
  toggleTheme: () => void;
  colors: typeof lightColors;
}

const lightColors = {
  background: '#FFFFFF',
  surface: '#F5F5F5',
  text: '#000000',
  textSecondary: '#666666',
  primary: '#007AFF',
  border: '#E5E5E5',
};

const darkColors = {
  background: '#1A1A1A',
  surface: '#2D2D2D',
  text: '#FFFFFF',
  textSecondary: '#A0A0A0',
  primary: '#0A84FF',
  border: '#3D3D3D',
};

const ThemeContext = createContext<ThemeContextValue | null>(null);

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  // DevTools emulation triggers colorScheme changes via setEmulatedMedia
  const systemColorScheme = useColorScheme();
  const [theme, setTheme] = useState<Theme>(systemColorScheme ?? 'light');

  useEffect(() => {
    // Listen for DevTools theme emulation changes
    const subscription = Appearance.addChangeListener(({ colorScheme }) => {
      if (colorScheme) {
        setTheme(colorScheme);
      }
    });
    return () => subscription?.remove();
  }, []);

  const toggleTheme = () => setTheme(prev => (prev === 'light' ? 'dark' : 'light'));
  const colors = theme === 'dark' ? darkColors : lightColors;

  return (
    <ThemeContext.Provider value={{ theme, toggleTheme, colors }}>
      {children}
    </ThemeContext.Provider>
  );
}

export function useTheme(): ThemeContextValue {
  const context = useContext(ThemeContext);
  if (!context) {
    throw new Error('useTheme must be used within ThemeProvider');
  }
  return context;
}

import React from 'react';
import { Pressable, Text, PlatformColor, Platform, StyleSheet } from 'react-native';

interface ThemedButtonProps {
  title: string;
  onPress: () => void;
}

export function ThemedButton({ title, onPress }: ThemedButtonProps) {
  return (
    <Pressable
      onPress={onPress}
      style={({ pressed }) => [
        styles.button,
        pressed && styles.pressed,
      ]}
      android_ripple={{
        // PlatformColor adapts to system theme automatically
        color: Platform.OS === 'android'
          ? PlatformColor('?attr/colorControlHighlight')
          : undefined,
        borderless: false,
        foreground: true,
      }}
    >
      <Text style={styles.text}>{title}</Text>
    </Pressable>
  );
}

const styles = StyleSheet.create({
  button: {
    padding: 16,
    backgroundColor: Platform.select({
      android: PlatformColor('?attr/colorPrimary'),
      default: '#007AFF',
    }),
    borderRadius: 8,
    alignItems: 'center',
  },
  pressed: { opacity: 0.8 },
  text: { color: '#FFFFFF', fontWeight: '600', fontSize: 16 },
});

import React, { useState, useEffect } from 'react';
import { Image, View, useWindowDimensions, StyleSheet } from 'react-native';

interface ResponsiveImageProps {
  uri: string;
  maxHeight?: number;
}

export function ResponsiveImage({ uri, maxHeight = 400 }: ResponsiveImageProps) {
  const { width: screenWidth } = useWindowDimensions();
  const [dimensions, setDimensions] = useState({ width: screenWidth, height: 200 });

  useEffect(() => {
    // getSize now returns true source dimensions, not downsampled values
    Image.getSize(
      uri,
      (width, height) => {
        const aspectRatio = width / height;
        let calculatedHeight = screenWidth / aspectRatio;
        
        // Constrain to maxHeight while maintaining aspect ratio
        if (calculatedHeight > maxHeight) {
          calculatedHeight = maxHeight;
        }
        
        setDimensions({
          width: screenWidth,
          height: calculatedHeight,
        });
      },
      (error) => {
        console.error('Failed to get image size:', error);
      }
    );
  }, [uri, screenWidth, maxHeight]);

  return (
    <View style={styles.container}>
      <Image
        source={{ uri }}
        style={{ width: dimensions.width, height: dimensions.height }}
        resizeMode="cover"
      />
    </View>
  );
}

const styles = StyleSheet.create({
  container: { width: '100%' },
});

import { useState, useCallback } from 'react';

interface DownloadProgress {
  loaded: number;
  total: number;
  percentage: number;
}

export function useLargeFileDownload() {
  const [progress, setProgress] = useState<DownloadProgress | null>(null);
  const [error, setError] = useState<string | null>(null);

  const downloadFile = useCallback(async (url: string): Promise<Blob | null> => {
    try {
      setError(null);
      setProgress({ loaded: 0, total: 0, percentage: 0 });

      const response = await fetch(url);
      
      if (!response.ok) {
        throw new Error(`HTTP ${response.status}: ${response.statusText}`);
      }

      const contentLength = response.headers.get('Content-Length');
      const total = contentLength ? parseInt(contentLength, 10) : 0;

      // NetworkingModule now handles large responses without OutOfMemoryError
      const reader = response.body?.getReader();
      if (!reader) {
        throw new Error('Response body is not readable');
      }

      const chunks: Uint8Array[] = [];
      let loaded = 0;

      while (true) {
        const { done, value } = await reader.read();
        if (done) break;
        
        chunks.push(value);
        loaded += value.length;
        
        setProgress({
          loaded,
          total,
          percentage: total > 0 ? Math.round((loaded / total) * 100) : 0,
        });
      }

      const blob = new Blob(chunks);
      setProgress({ loaded, total, percentage: 100 });
      return blob;
    } catch (err) {
      const message = err instanceof Error ? err.message : 'Download failed';
      setError(message);
      return null;
    }
  }, []);

  return { downloadFile, progress, error };
}

type MessageHandler = (data: string) => void;
type ErrorHandler = (error: Event) => void;

interface WebSocketOptions {
  url: string;
  sessionCookie: string;
  onMessage: MessageHandler;
  onError?: ErrorHandler;
}

export function createAuthenticatedWebSocket({
  url,
  sessionCookie,
  onMessage,
  onError,
}: WebSocketOptions): WebSocket {
  // Cookie header now reaches the server correctly in 0.86
  const ws = new WebSocket(url, undefined, {
    headers: {
      Cookie: sessionCookie,
      // Additional headers as needed
      'X-Client-Version': '1.0.0',
    },
  });

  ws.onopen = () => {
    console.log('WebSocket connected with session cookie');
  };

  ws.onmessage = (event) => {
    if (typeof event.data === 'string') {
      onMessage(event.data);
    }
  };

  ws.onerror = (error) => {
    console.error('WebSocket error:', error);
    onError?.(error);
  };

  ws.onclose = (event) => {
    console.log(`WebSocket closed: ${event.code} ${event.reason}`);
  };

  return ws;
}