Location services in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the output of this code when location permission is denied?

Consider this Kotlin snippet for requesting location permission in an Android app. What will the app display if the user denies the location permission?

Android Kotlin

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

requestPermissionLauncher.launch(Manifest.permission.ACCESS_FINE_LOCATION)

A The TextView shows "Permission denied"

B The TextView shows "Permission granted"

C The app crashes with SecurityException

D The TextView remains empty

💡 Hint

Think about what happens when the permission callback receives false.

If the user denies the permission, the callback receives false, so the TextView text is set to "Permission denied".

🧠 Conceptual

intermediate

Which location provider gives the most accurate location?

Android offers different location providers. Which one typically provides the most accurate location data?

A GPS provider (uses satellites)

B Network provider (uses Wi-Fi and cell towers)

C Passive provider (listens to other apps' location requests)

D Bluetooth provider

💡 Hint

Think about which source uses satellites directly.

The GPS provider uses satellites and usually gives the most accurate location outdoors.

❓ lifecycle

advanced

What happens if you start location updates in onCreate and never stop them?

In an Android app, if you start location updates in the onCreate method of an Activity and never stop them, what is the likely result?

A Location updates only run while Activity is visible

B Location updates stop automatically when Activity is paused

C App crashes with IllegalStateException

D Location updates continue, causing battery drain even when app is in background

💡 Hint

Consider what happens if you don't remove location updates explicitly.

Without stopping location updates, they continue running, draining battery even if the app is not visible.

❓ navigation

advanced

How to navigate to app settings to enable location permission?

Which Intent action correctly opens the app's settings page so the user can enable location permission manually?

A Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION)

B Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply { data = Uri.fromParts("package", packageName, null) }

C Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS)

D Intent(Settings.ACTION_WIFI_SETTINGS)

💡 Hint

Think about how to open the specific app's settings page.

Using ACTION_APPLICATION_DETAILS_SETTINGS with the app package Uri opens the app's settings page.

🔧 Debug

expert

Why does this location request code cause a crash?

Examine this Kotlin code snippet. Why does it cause a crash when run?

Android Kotlin

val fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
fusedLocationClient.lastLocation.addOnSuccessListener { location ->
  if (location != null) {
    textView.text = "Lat: ${location.latitude}, Lon: ${location.longitude}"
  } else {
    textView.text = "Location not available"
  }
}

A It crashes because addOnSuccessListener is not a valid method

B It crashes because fusedLocationClient is not initialized properly

C It crashes because location can be null and code does not check for null

D It crashes because textView is not declared

💡 Hint

Think about what happens if the location is not available yet.

The lastLocation can be null if no location is cached yet. Accessing latitude without null check causes NullPointerException.

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