React Native Academy · Ders

expo-location ile GPS Konumunu Okuma

Ön plan konum izni isteyin, getCurrentPositionAsync ile geçerli koordinatları alın ve enlem ile boylamı ekranda görüntüleyin.

expo-location ile GPS Konumunu Okuma, CoddyKit'te ücretsiz bir React Native Academy dersidir. Bu, 4 dersinin 2. dersidir. Aşağıdan dersin tamamını ücretsiz okuyabilir, sonra tarayıcıda yerleşik kod editörü ve 7/24 yapay zeka koçu ile uygulamalı olarak pratik yapabilirsin. Bu, React Native Academy öğrenme yolunun bir parçasıdır ve ilerlemeniz web ve CoddyKit uygulaması arasında senkronize olur. React Native Academy kursu toplamda 4 dersten oluşur.

Bu dersin bazı bölümleri henüz çevrilmemiş olup İngilizce olarak gösterilmektedir.

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.

Sıkça Sorulan Sorular

“expo-location ile GPS Konumunu Okuma” dersi ücretsiz mi?

Evet — “expo-location ile GPS Konumunu Okuma” dersin tüm metni burada web'de ücretsiz olarak okunabilir. Etkileşimli olarak pratik yapmak (yerleşik kod editörü ve 7/24 yapay zeka koçu) ve React Native Academy kursunun geri kalanını açmak için CoddyKit PRO'ya yükselt. React Native Academy kursu toplamda 4 dersten oluşur.

“expo-location ile GPS Konumunu Okuma” dersinde ne öğreneceğim?

Ön plan konum izni isteyin, getCurrentPositionAsync ile geçerli koordinatları alın ve enlem ile boylamı ekranda görüntüleyin. React Native Academy ile uygulamalı kodu tarayıcıda doğrudan çalıştırarak pratik yaparsın ve 7/24 yapay zeka koçu dersi çalışırken sorularını yanıtlar.

React Native Academy öğrenmeye başlamak için deneyim gerekli mi?

Önceden deneyim gerekmez. CoddyKit'te React Native Academy, başlangıçtan ileri seviyeye kadar yapılandırıldığı için buradan başlayabilir veya başından başlayıp kendi hızında ilerleme yapabilirsin. Bu, 4 dersinin 2. dersidir.

“expo-location ile GPS Konumunu Okuma” dersi ne kadar sürer?

Çoğu CoddyKit dersi yaklaşık 5–10 dakika sürer. Her biri kısa ve etkileşimli olduğu için sabit ilerleme yaparsın ve web ile uygulama arasında tam olarak bıraktığın yerden devam edebilirsin.

Bu React Native Academy dersinde kod yazıp çalıştırabilir miyim?

Evet. Her React Native Academy dersi yerleşik bir kod editörü içerir, bu sayede tarayıcıda gerçek kod yazıp çalıştırabilir ve anlık yapay zeka geri bildirimi alırsın — yerel kurulum gerekli değildir.

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