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React Native Academy · Pelajaran

Membaca Lokasi GPS dengan expo-location

Minta izin lokasi latar depan, dapatkan koordinat saat ini dengan getCurrentPositionAsync, lalu tampilkan garis lintang dan garis bujur di layar.

Membaca Lokasi GPS dengan expo-location adalah pelajaran React Native Academy gratis di CoddyKit. Ini adalah pelajaran 2 dari 4. Kamu bisa membaca pelajaran lengkapnya di bawah secara gratis — lalu praktikkan langsung di browser dengan editor kode bawaan dan tutor AI 24/7. Ini adalah bagian dari jalur belajar React Native Academy, dan progresmu tersinkronisasi di web dan aplikasi CoddyKit. Kursus React Native Academy mencakup 4 pelajaran total.

Bagian dari pelajaran ini belum diterjemahkan dan ditampilkan dalam bahasa Inggris.

What Is expo-location?

expo-location provides an API to read the device's geographic position using GPS, Wi-Fi triangulation, and cell tower data. It works on both iOS and Android without writing native code. You can get a one-time position fix, watch the location as the user moves, or geocode an address to coordinates and vice versa.

Installing expo-location

Use the Expo install command to get the SDK-compatible version of expo-location. In managed Expo projects, the native module is linked automatically. For bare React Native projects, you must also run pod install on iOS and update AndroidManifest.xml with the location permission declarations.

npx expo install expo-location

Requesting Foreground Location Permission

Location access requires explicit user permission. Call Location.requestForegroundPermissionsAsync() to ask for permission to read location while the app is in the foreground. Check the status field of the returned object — only proceed if it equals 'granted'. The hook version Location.useForegroundPermissions() simplifies this in functional components.

import * as Location from 'expo-location';

const [permission, requestPermission] = Location.useForegroundPermissions();

if (!permission) return <ActivityIndicator />;

if (!permission.granted) {
  return (
    <View>
      <Text>Location access is needed to show your position.</Text>
      <Button title='Allow Location' onPress={requestPermission} />
    </View>
  );
}

Getting the Current Position Once

Location.getCurrentPositionAsync() performs a single GPS fix and returns a LocationObject containing coords.latitude, coords.longitude, coords.accuracy (in meters), and a timestamp. Use this for one-time lookups like 'find nearby restaurants' where you do not need continuous tracking.

const [location, setLocation] = React.useState(null);

async function fetchLocation() {
  const loc = await Location.getCurrentPositionAsync({
    accuracy: Location.Accuracy.Balanced,
  });
  setLocation(loc);
  console.log('Lat:', loc.coords.latitude);
  console.log('Lng:', loc.coords.longitude);
  console.log('Accuracy:', loc.coords.accuracy, 'meters');
}

Accuracy Levels

expo-location provides several accuracy presets via Location.Accuracy. Use Lowest or Low for coarse location with minimal battery impact, Balanced for general use, and High or BestForNavigation when you need precise GPS coordinates for turn-by-turn navigation. Higher accuracy drains battery faster, so choose appropriately for your use case.

// Coarse — fast, low battery, uses Wi-Fi/cell
Location.Accuracy.Lowest      // ~3 km
Location.Accuracy.Low         // ~1 km
Location.Accuracy.Balanced    // ~100 m — good default

// Precise — uses GPS, more battery
Location.Accuracy.High        // ~10 m
Location.Accuracy.Highest     // ~1 m
Location.Accuracy.BestForNavigation // highest + sensors

Watching the Location Continuously

Location.watchPositionAsync starts a subscription that calls a callback every time the device's position changes by a specified distance or time interval. It returns a subscription object with a remove() method. Always call remove() in a useEffect cleanup function to stop tracking when the component unmounts and save battery.

useEffect(() => {
  let subscription: Location.LocationSubscription;

  async function startWatching() {
    subscription = await Location.watchPositionAsync(
      {
        accuracy: Location.Accuracy.High,
        distanceInterval: 10, // update every 10 meters
        timeInterval: 5000,   // or every 5 seconds
      },
      (loc) => setLocation(loc)
    );
  }

  startWatching();
  return () => subscription?.remove(); // cleanup on unmount
}, []);

Displaying Coordinates on Screen

Once you have a location object, display the coordinates in a human-readable format. Round latitude and longitude to 5-6 decimal places for readability — that corresponds to roughly 1-meter precision. Display the accuracy value so users understand how precise the reading is, especially on devices that cannot get a good GPS fix indoors.

export default function LocationDisplay() {
  const [location, setLocation] = React.useState(null);
  // ... permission check and fetch ...

  if (!location) return <Button title='Get Location' onPress={fetchLocation} />;

  return (
    <View>
      <Text>Latitude: {location.coords.latitude.toFixed(6)}</Text>
      <Text>Longitude: {location.coords.longitude.toFixed(6)}</Text>
      <Text>Accuracy: {location.coords.accuracy?.toFixed(0)} m</Text>
    </View>
  );
}

Reverse Geocoding: Coordinates to Address

Location.reverseGeocodeAsync converts latitude and longitude coordinates into a human-readable address. It returns an array of LocationGeocodedAddress objects with fields like street, city, region, country, and postalCode. Use the first result — it is the most likely match for the given coordinates.

async function getAddress(latitude: number, longitude: number) {
  const results = await Location.reverseGeocodeAsync({ latitude, longitude });
  if (results.length > 0) {
    const addr = results[0];
    return [addr.street, addr.city, addr.region, addr.country]
      .filter(Boolean)
      .join(', ');
  }
  return 'Unknown location';
}

Forward Geocoding: Address to Coordinates

Location.geocodeAsync converts a text address into latitude and longitude. This is useful for features like 'search nearby' where users type a location name. The function returns an array of results (multiple matches are possible for ambiguous addresses) each containing latitude, longitude, and altitude.

async function searchAddress(address: string) {
  const results = await Location.geocodeAsync(address);
  if (results.length > 0) {
    const { latitude, longitude } = results[0];
    console.log('Coordinates:', latitude, longitude);
    return { latitude, longitude };
  }
  return null;
}

Handling Location Errors

Location requests can fail when the user is indoors, when the device's GPS is disabled, or on simulators that do not have a simulated location set. Wrap location calls in try-catch and show a fallback UI. Check Location.hasServicesEnabledAsync() before requesting a position to detect when the device's location services are turned off in system settings.

async function fetchLocationSafe() {
  const enabled = await Location.hasServicesEnabledAsync();
  if (!enabled) {
    Alert.alert('Location Off', 'Please enable Location Services in Settings.');
    return;
  }
  try {
    const loc = await Location.getCurrentPositionAsync({
      accuracy: Location.Accuracy.Balanced,
    });
    setLocation(loc);
  } catch (err) {
    Alert.alert('Error', 'Could not get your location. Please try again.');
  }
}

Background Location Tracking

Tracking location when the app is in the background requires background location permission (requestBackgroundPermissionsAsync) and a background task defined with expo-task-manager. This is only needed for apps like fitness trackers or delivery apps. Apple and Google have strict review requirements for apps that use background location, so only request it if the feature is core to your app.

Quick Check

Test your understanding of React Native Mobile Development concepts from this lesson.

Lesson Recap

In this lesson you learned: requestForegroundPermissionsAsync must be called and granted before any location reading is possible, getCurrentPositionAsync performs a one-time position fix while watchPositionAsync tracks continuous movement, and reverseGeocodeAsync converts coordinates to a human-readable address. Next up we explore scheduling local notifications.

Pertanyaan yang Sering Diajukan

Apakah pelajaran “Membaca Lokasi GPS dengan expo-location” gratis?

Ya — teks lengkap “Membaca Lokasi GPS dengan expo-location” gratis dibaca di sini di web. Untuk praktiknya secara interaktif (editor kode bawaan dan tutor AI 24/7) dan buka sisa kursus React Native Academy, upgrade ke CoddyKit PRO. Kursus React Native Academy mencakup 4 pelajaran total.

Apa yang akan aku pelajari di “Membaca Lokasi GPS dengan expo-location”?

Minta izin lokasi latar depan, dapatkan koordinat saat ini dengan getCurrentPositionAsync, lalu tampilkan garis lintang dan garis bujur di layar. Kamu berlatih React Native Academy dengan kode praktik yang langsung kamu jalankan di browser, dan tutor AI 24/7 menjawab pertanyaanmu saat kamu mengerjakan pelajaran ini.

Apakah aku perlu pengalaman untuk memulai React Native Academy?

Tidak diperlukan pengalaman sebelumnya. React Native Academy di CoddyKit dirancang untuk pemula hingga pelajar tingkat lanjut, jadi kamu bisa memulai di sini atau dari awal dan belajar sesuai kecepatan kamu sendiri. Ini adalah pelajaran 2 dari 4.

Berapa lama pelajaran “Membaca Lokasi GPS dengan expo-location” memakan waktu?

Sebagian besar pelajaran CoddyKit memakan waktu sekitar 5–10 menit. Setiap pelajaran ringkas dan interaktif, jadi kamu membuat kemajuan stabil dan melanjutkan dari tempat kamu tinggalkan di web dan aplikasi.

Bisakah aku menulis dan menjalankan kode dalam pelajaran React Native Academy ini?

Ya. Setiap pelajaran React Native Academy menyertakan editor kode bawaan, jadi kamu menulis dan menjalankan kode nyata langsung di browser dan mendapatkan umpan balik AI instan — tidak diperlukan penyiapan lokal.

Semua pelajaran dalam kursus ini

  1. Mengakses Kamera dengan expo-camera
  2. Membaca Lokasi GPS dengan expo-location
  3. Menjadwalkan Notifikasi Lokal
  4. Menangani Izin dengan Baik
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