iOS Simulator & Android Emulator

# Start Metro, then open the default virtual device
npx expo start
# Press i → iOS Simulator (macOS only)
# Press a → Android Emulator (ANDROID_HOME + one AVD required)
 
# Pick a specific device interactively
# Shift+I → iOS simulator list
# Shift+A → Android emulator / device list
 
# Launch directly without the interactive menu
npx expo start --ios
npx expo start --android
 
# Capture a screenshot from the booted simulator/emulator
xcrun simctl io booted screenshot ./snapshots/ios-$(date +%Y%m%d-%H%M%S).png
adb exec-out screencap -p > ./snapshots/android-$(date +%Y%m%d-%H%M%S).png

#!/usr/bin/env bash
# scripts/device-matrix.sh - boot key simulators, capture snapshots, log dimensions
set -euo pipefail
 
OUT_DIR="${1:-./snapshots/matrix-$(date +%Y%m%d)}"
mkdir -p "$OUT_DIR"
 
echo "▶ Starting Metro in background (dev-client assumed)…"
npx expo start --dev-client --non-interactive &
METRO_PID=$!
sleep 8
 
capture_ios() {
  local UDID="$1"
  local LABEL="$2"
  xcrun simctl boot "$UDID" 2>/dev/null || true
  xcrun simctl bootstatus "$UDID" -b
  # Expo CLI targets the most recently opened simulator
  open -a Simulator --args -CurrentDeviceUDID "$UDID"
  sleep 4
  xcrun simctl io "$UDID" screenshot "$OUT_DIR/ios-${LABEL}.png"
  xcrun simctl list devices booted | grep "$UDID" || true
}
 
capture_android() {
  local AVD="$1"
  local LABEL="$2"
  emulator -avd "$AVD" -no-snapshot-load -no-boot-anim &
  adb wait-for-device
  while [ "$(adb shell getprop sys.boot_completed | tr -d '\r')" != "1" ]; do sleep 2; done
  adb exec-out screencap -p > "$OUT_DIR/android-${LABEL}.png"
  adb emu kill
}
 
# iOS matrix - list available runtimes first: xcrun simctl list devices available
capture_ios "iPhone-16-Pro" "iphone-16-pro" || echo "⚠️  Create iPhone 16 Pro in Xcode > Settings > Components"
capture_ios "iPad-mini-A17-Pro" "ipad-mini" || echo "⚠️  Create iPad mini in Xcode Components"
 
# Android matrix - list AVDs: emulator -list-avds
capture_android "Pixel_8_API_36" "pixel-8" || echo "⚠️  Create Pixel 8 API 36 AVD in Android Studio"
 
kill "$METRO_PID" 2>/dev/null || true
echo "✅ Snapshots written to $OUT_DIR"

// App.tsx - on-screen size label for snapshot review
import { StyleSheet, Text, useWindowDimensions, View } from "react-native";
import { useSafeAreaInsets } from "react-native-safe-area-context";
 
export default function App() {
  const { width, height, fontScale } = useWindowDimensions();
  const insets = useSafeAreaInsets();
 
  return (
    <View style={[styles.screen, { paddingTop: insets.top, paddingBottom: insets.bottom }]}>
      <Text style={styles.title}>Device matrix probe</Text>
      <Text style={styles.row}>Window: {Math.round(width)} × {Math.round(height)}</Text>
      <Text style={styles.row}>Font scale: {fontScale.toFixed(2)}</Text>
      <Text style={styles.row}>Safe top: {insets.top}px · bottom: {insets.bottom}px</Text>
      <View style={styles.card}>
        <Text>Card should stay inside safe area on notched phones and tablets.</Text>
      </View>
    </View>
  );
}
 
const styles = StyleSheet.create({
  screen: { flex: 1, paddingHorizontal: 16, backgroundColor: "#f8fafc" },
  title: { fontSize: 22, fontWeight: "700", marginBottom: 12 },
  row: { fontSize: 14, color: "#475569", marginBottom: 4 },
  card: { marginTop: 24, padding: 16, borderRadius: 12, backgroundColor: "#e0e7ff" },
});

# macOS Android env (add to ~/.zshrc)
export ANDROID_HOME=$HOME/Library/Android/sdk
export PATH=$PATH:$ANDROID_HOME/emulator:$ANDROID_HOME/platform-tools
 
# Open Simulator manually when Expo CLI appears stuck
open -a Simulator

import * as Device from "expo-device";
 
// expo-device is the reliable check - simulators/emulators return isDevice === false
if (__DEV__ && !Device.isDevice) {
  console.log("Virtual device - validate camera, push, and performance on hardware.");
}