Location services in Android Kotlin

Introduction

Location services help your app find where the user is on the map. This lets your app give directions, show nearby places, or customize content based on location.

Showing the user's current position on a map in a travel app.

Finding nearby restaurants or stores in a shopping app.

Tracking a delivery or ride in real time.

Providing weather updates based on the user's location.

Helping users check in or tag their location in social apps.

Syntax

Android Kotlin

val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
fusedLocationClient.lastLocation
    .addOnSuccessListener { location ->
        if (location != null) {
            val latitude = location.latitude
            val longitude = location.longitude
            // Use latitude and longitude
        }
    }

Use getFusedLocationProviderClient to get the location provider.

Always check if the location is not null before using it.

Examples

Get the last known location and print latitude and longitude.

Android Kotlin

val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
fusedLocationClient.lastLocation.addOnSuccessListener { location ->
    if (location != null) {
        println("Lat: ${location.latitude}, Lon: ${location.longitude}")
    }
}

Use Kotlin's safe call and let to handle nullable location.

Android Kotlin

val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
fusedLocationClient.lastLocation.addOnSuccessListener { location ->
    location?.let {
        val lat = it.latitude
        val lon = it.longitude
        // Use lat and lon here
    }
}

Sample App

This app asks for location permission. If allowed, it shows the user's last known latitude and longitude on the screen. If permission is denied or location is unavailable, it shows a message.

Android Kotlin

import android.Manifest
import android.content.pm.PackageManager
import android.os.Bundle
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity
import androidx.core.content.ContextCompat
import com.google.android.gms.location.LocationServices
import android.widget.TextView

class MainActivity : AppCompatActivity() {
    private lateinit var locationText: TextView

    private val requestPermissionLauncher = registerForActivityResult(
        ActivityResultContracts.RequestPermission()
    ) { isGranted: Boolean ->
        if (isGranted) {
            getLastLocation()
        } else {
            locationText.text = "Permission denied"
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        locationText = TextView(this).apply {
            textSize = 18f
            setPadding(16, 16, 16, 16)
        }
        setContentView(locationText)

        when {
            ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED -> {
                getLastLocation()
            }
            else -> {
                requestPermissionLauncher.launch(Manifest.permission.ACCESS_FINE_LOCATION)
            }
        }
    }

    private fun getLastLocation() {
        val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
        fusedLocationClient.lastLocation.addOnSuccessListener { location ->
            if (location != null) {
                locationText.text = "Latitude: ${location.latitude}\nLongitude: ${location.longitude}"
            } else {
                locationText.text = "Location not available"
            }
        }
    }
}

Important Notes

Always request location permission at runtime for Android 6.0 and above.

Last known location might be null if location was never requested before.

For continuous updates, use location request APIs instead of just last location.

Summary

Location services let your app find the user's position.

Use FusedLocationProviderClient to get location easily.

Always handle permissions and null location safely.

Practice

1.

What is the main purpose of FusedLocationProviderClient in Android Kotlin?

easy

A. To get the user's current location easily

B. To display a map on the screen

C. To send SMS messages

D. To manage app permissions

Solution

1. Step 1: Understand the role of FusedLocationProviderClient

   This client combines different location sources to provide the best location data efficiently.

2. Step 2: Identify its main use

   It is used to get the user's current location easily without managing multiple providers manually.

3. Final Answer:

   To get the user's current location easily -> Option A

4. Quick Check:

   Location client = A [OK]

Hint: FusedLocationProviderClient is for getting location, not maps or SMS [OK]

Common Mistakes:

• Confusing location client with map display
• Thinking it manages permissions directly
• Assuming it sends messages

2.

Which of the following is the correct way to request location updates using FusedLocationProviderClient?

val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
fusedLocationClient._____

easy

A. requestLocationUpdates(locationRequest, locationCallback, Looper.getMainLooper())

B. getLastKnownLocation()

C. startLocationService()

D. requestPermissions()

Solution

1. Step 1: Identify method to request continuous updates

   The method requestLocationUpdates is used to get ongoing location updates with a request and callback.

2. Step 2: Check other options

   getLastKnownLocation() gets a single last location, startLocationService() is not a valid method, and requestPermissions() is unrelated to location updates.

3. Final Answer:

   requestLocationUpdates(locationRequest, locationCallback, Looper.getMainLooper()) -> Option A

4. Quick Check:

   Request updates = D [OK]

Hint: Request updates use requestLocationUpdates with callback [OK]

Common Mistakes:

• Using getLastKnownLocation for continuous updates
• Calling non-existent startLocationService method
• Confusing permission requests with location updates

3.

What will the following Kotlin code print if the location is successfully retrieved?

fusedLocationClient.lastLocation.addOnSuccessListener { location ->
    if (location != null) {
        println("Lat: ${location.latitude}, Lon: ${location.longitude}")
    } else {
        println("Location not found")
    }
}

medium

A. NullPointerException

B. Location not found

C. Syntax error

D. Lat: [latitude], Lon: [longitude]

Solution

1. Step 1: Understand addOnSuccessListener behavior

   This listener runs when location retrieval succeeds, passing a Location object or null.

2. Step 2: Check the null condition

   If location is not null, it prints latitude and longitude; otherwise, it prints "Location not found".

3. Final Answer:

   Lat: [latitude], Lon: [longitude] -> Option D

4. Quick Check:

   Non-null location prints coordinates = C [OK]

Hint: Non-null location prints coordinates, else prints not found [OK]

Common Mistakes:

• Assuming location is always null
• Expecting exceptions without null checks
• Confusing syntax errors with runtime behavior

4.

Identify the error in this Kotlin snippet for requesting location permission:

if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
    ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.ACCESS_FINE_LOCATION), 1)
} else {
    startLocationUpdates()
}

medium

A. Using wrong permission constant

B. Calling startLocationUpdates() before permission check

C. Missing override for onRequestPermissionsResult to handle response

D. No error, code is correct

Solution

1. Step 1: Check permission request flow

   The code requests permission if not granted, which is correct.

2. Step 2: Verify handling of permission result

   Missing override of onRequestPermissionsResult means app won't know if permission was granted or denied.

3. Final Answer:

   Missing override for onRequestPermissionsResult to handle response -> Option C

4. Quick Check:

   Permission result handler needed = B [OK]

Hint: Always override onRequestPermissionsResult after requesting permissions [OK]

Common Mistakes:

• Forgetting to handle permission result
• Using wrong permission string
• Calling location updates before permission granted

5.

You want to get the user's location only once and handle the case when location is null. Which Kotlin code snippet correctly does this?

val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
fusedLocationClient.lastLocation.addOnSuccessListener { location ->
    _____
}

hard

A. useLocation(location!!) // force unwrap without null check

B. if (location != null) { useLocation(location) } else { showError("No location") }

C. showError("No location") // ignore non-null case

D. startLocationUpdates() // request continuous updates instead

Solution

1. Step 1: Check for null safety

   Using if (location != null) ensures safe use of location without crashing.

2. Step 2: Handle null case properly

   Showing an error message if location is null informs the user gracefully.

3. Final Answer:

   if (location != null) { useLocation(location) } else { showError("No location") } -> Option B

4. Quick Check:

   Null check with fallback = A [OK]

Hint: Always check for null before using location to avoid crashes [OK]

Common Mistakes:

• Forcing unwrap without null check causing crash
• Ignoring null case leading to no feedback
• Requesting continuous updates when only one location needed