Android Location, Camera & Sensors — GPS, Fused Location, CameraX

Hardware Overview

Modern Android devices include GPS chips, cameras, and motion sensors. Apps access them through Android APIs with appropriate runtime permissions and battery-conscious patterns.

Location: GPS / Network / Fused Location Provider → Lat/Lng Camera: CameraX → Preview + ImageCapture → File / Bitmap Sensors: SensorManager → Accelerometer, Gyroscope → Float arrays

Feature	Recommended API	Key Permission
Location	Fused Location Provider (Play Services)	`ACCESS_FINE_LOCATION`
Camera	CameraX	`CAMERA`
Motion sensors	SensorManager	None (normal permission)

1GPS Location

GPS (Global Positioning System) uses satellite signals to determine latitude, longitude, altitude, and accuracy. Android exposes location through the LocationManager and the higher-level Fused Location Provider.

Manifest permissions

XML — AndroidManifest.xml<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

<!-- Background location (only if needed — requires extra approval) -->
<uses-permission android:name="android.permission.ACCESS_BACKGROUND_LOCATION" />

LocationManager (legacy approach)

Kotlin — Basic GPS via LocationManager@SuppressLint("MissingPermission")
fun getLastKnownGpsLocation(context: Context): Location? {
    val locationManager = context.getSystemService(Context.LOCATION_SERVICE) as LocationManager

    val isGpsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)
    if (!isGpsEnabled) {
        Log.w("GPS", "GPS provider is disabled")
        return null
    }

    return locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER)
}

@SuppressLint("MissingPermission")
fun requestGpsUpdates(context: Context, callback: (Location) -> Unit) {
    val locationManager = context.getSystemService(Context.LOCATION_SERVICE) as LocationManager
    val listener = LocationListener { location -> callback(location) }

    locationManager.requestLocationUpdates(
        LocationManager.GPS_PROVIDER,
        5000L,   // min time ms
        10f,     // min distance meters
        listener
    )
}

Location object properties

Property	Description
`latitude` / `longitude`	Coordinates in decimal degrees
`accuracy`	Radius of uncertainty in meters
`altitude`	Height above sea level (if available)
`speed`	Ground speed in m/s
`time`	UTC timestamp of fix

2Fused Location Provider

The Fused Location Provider (Google Play Services) intelligently combines GPS, Wi-Fi, and cell towers for accurate, battery-efficient location. It is the recommended approach for most apps.

Gradle dependency

Kotlin — app/build.gradle.ktsdependencies {
    implementation("com.google.android.gms:play-services-location:21.1.0")
}

Get last known location

Kotlin — FusedLocationProviderClient@SuppressLint("MissingPermission")
fun fetchLastLocation(activity: ComponentActivity, onResult: (Location?) -> Unit) {
    val fusedClient = LocationServices.getFusedLocationProviderClient(activity)

    fusedClient.lastLocation.addOnSuccessListener { location ->
        if (location != null) {
            Log.d("Location", "Lat: ${location.latitude}, Lng: ${location.longitude}")
            Log.d("Location", "Accuracy: ${location.accuracy}m")
        }
        onResult(location)
    }.addOnFailureListener { e ->
        Log.e("Location", "Failed to get location", e)
        onResult(null)
    }
}

Request location updates

Kotlin — Continuous location updatesclass MapActivity : AppCompatActivity() {

    private lateinit var fusedClient: FusedLocationProviderClient
    private lateinit var locationCallback: LocationCallback

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        fusedClient = LocationServices.getFusedLocationProviderClient(this)

        locationCallback = object : LocationCallback() {
            override fun onLocationResult(result: LocationResult) {
                result.lastLocation?.let { location ->
                    binding.tvCoords.text =
                        "Lat: ${location.latitude}, Lng: ${location.longitude}"
                }
            }
        }
    }

    @SuppressLint("MissingPermission")
    fun startLocationUpdates() {
        val request = LocationRequest.Builder(
            Priority.PRIORITY_HIGH_ACCURACY, 5000L
        )
            .setMinUpdateIntervalMillis(2000L)
            .build()

        fusedClient.requestLocationUpdates(request, locationCallback, mainLooper)
    }

    override fun onPause() {
        super.onPause()
        fusedClient.removeLocationUpdates(locationCallback)
    }
}

Priority options

Priority	Behavior
`PRIORITY_HIGH_ACCURACY`	GPS when possible — maps, navigation
`PRIORITY_BALANCED_POWER_ACCURACY`	Wi-Fi + cell — city-level accuracy
`PRIORITY_LOW_POWER`	Cell towers only — minimal battery
`PRIORITY_PASSIVE`	Only when other apps request location

3Camera API

CameraX is the modern Jetpack camera library — simpler than the legacy Camera2 API, with lifecycle-aware binding, preview, and capture use cases.

Gradle dependencies

Kotlin — app/build.gradle.ktsval cameraxVersion = "1.3.1"
dependencies {
    implementation("androidx.camera:camera-core:$cameraxVersion")
    implementation("androidx.camera:camera-camera2:$cameraxVersion")
    implementation("androidx.camera:camera-lifecycle:$cameraxVersion")
    implementation("androidx.camera:camera-view:$cameraxVersion")
}

Layout with PreviewView

XML — activity_camera.xml<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.camera.view.PreviewView
        android:id="@+id/previewView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toTopOf="@id/btnCapture"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <Button
        android:id="@+id/btnCapture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/capture"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginBottom="32dp" />

</androidx.constraintlayout.widget.ConstraintLayout>

Start camera preview

Kotlin — CameraActivity.kt (preview setup)class CameraActivity : AppCompatActivity() {

    private lateinit var cameraProvider: ProcessCameraProvider
    private var imageCapture: ImageCapture? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_camera)

        val cameraProviderFuture = ProcessCameraProvider.getInstance(this)
        cameraProviderFuture.addListener({
            cameraProvider = cameraProviderFuture.get()
            startCamera()
        }, ContextCompat.getMainExecutor(this))
    }

    private fun startCamera() {
        val preview = Preview.Builder().build().also {
            it.setSurfaceProvider(binding.previewView.surfaceProvider)
        }

        imageCapture = ImageCapture.Builder()
            .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
            .build()

        val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

        try {
            cameraProvider.unbindAll()
            cameraProvider.bindToLifecycle(
                this, cameraSelector, preview, imageCapture
            )
        } catch (e: Exception) {
            Log.e("CameraX", "Use case binding failed", e)
        }
    }
}

4Capturing Images

Capture photos to a file or memory buffer with CameraX ImageCapture, or use the system camera intent for a simpler delegate approach.

Capture to file with CameraX

Kotlin — takePhoto() to fileprivate fun capturePhoto() {
    val capture = imageCapture ?: return

    val photoFile = File(
        getExternalFilesDir(Environment.DIRECTORY_PICTURES),
        "IMG_${System.currentTimeMillis()}.jpg"
    )

    val outputOptions = ImageCapture.OutputFileOptions.Builder(photoFile).build()

    capture.takePicture(
        outputOptions,
        ContextCompat.getMainExecutor(this),
        object : ImageCapture.OnImageSavedCallback {
            override fun onImageSaved(output: ImageCapture.OutputFileResults) {
                Toast.makeText(
                    this@CameraActivity,
                    "Saved: ${photoFile.absolutePath}",
                    Toast.LENGTH_SHORT
                ).show()
                binding.ivThumbnail.setImageURI(Uri.fromFile(photoFile))
            }

            override fun onError(exception: ImageCaptureException) {
                Log.e("CameraX", "Capture failed", exception)
            }
        }
    )
}

System camera intent (simple approach)

Kotlin — Take picture via system cameraclass ProfileActivity : AppCompatActivity() {

    private var photoUri: Uri? = null

    private val takePictureLauncher = registerForActivityResult(
        ActivityResultContracts.TakePicture()
    ) { success ->
        if (success && photoUri != null) {
            binding.ivProfile.setImageURI(photoUri)
        }
    }

    fun launchCamera() {
        val photoFile = File.createTempFile(
            "profile_", ".jpg",
            getExternalFilesDir(Environment.DIRECTORY_PICTURES)
        )
        photoUri = FileProvider.getUriForFile(
            this, "${packageName}.fileprovider", photoFile
        )
        takePictureLauncher.launch(photoUri)
    }
}

FileProvider setup

XML — res/xml/file_paths.xml + manifest<paths>
    <external-files-path name="photos" path="Pictures/" />
</paths>

<!-- AndroidManifest.xml -->
<provider
    android:name="androidx.core.content.FileProvider"
    android:authorities="${applicationId}.fileprovider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/file_paths" />
</provider>

Pick from gallery

Kotlin — Pick image from galleryprivate val pickImageLauncher = registerForActivityResult(
    ActivityResultContracts.GetContent()
) { uri: Uri? ->
    uri?.let { binding.ivProfile.setImageURI(it) }
}

binding.btnGallery.setOnClickListener {
    pickImageLauncher.launch("image/*")
}

5SensorManager

SensorManager gives access to device hardware sensors — accelerometer, gyroscope, light, proximity, and more. Register listeners in onResume and unregister in onPause to save battery.

Basic sensor setup

Kotlin — SensorActivity.ktclass SensorActivity : AppCompatActivity(), SensorEventListener {

    private lateinit var sensorManager: SensorManager
    private var accelerometer: Sensor? = null
    private var gyroscope: Sensor? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_sensor)

        sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager
        accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER)
        gyroscope = sensorManager.getDefaultSensor(Sensor.TYPE_GYROSCOPE)

        if (accelerometer == null) {
            Toast.makeText(this, "No accelerometer on this device", Toast.LENGTH_SHORT).show()
        }
    }

    override fun onResume() {
        super.onResume()
        accelerometer?.let {
            sensorManager.registerListener(this, it, SensorManager.SENSOR_DELAY_UI)
        }
        gyroscope?.let {
            sensorManager.registerListener(this, it, SensorManager.SENSOR_DELAY_UI)
        }
    }

    override fun onPause() {
        super.onPause()
        sensorManager.unregisterListener(this)
    }

    override fun onSensorChanged(event: SensorEvent?) {
        event ?: return
        when (event.sensor.type) {
            Sensor.TYPE_ACCELEROMETER -> handleAccelerometer(event.values)
            Sensor.TYPE_GYROSCOPE -> handleGyroscope(event.values)
        }
    }

    override fun onAccuracyChanged(sensor: Sensor?, accuracy: Int) {}
}

Sensor delay constants

Constant	Rate	Use Case
`SENSOR_DELAY_FASTEST`	~0 ms (max rate)	Games, high-frequency apps
`SENSOR_DELAY_GAME`	~20 ms	Interactive games
`SENSOR_DELAY_UI`	~60 ms	UI animations, shake detection
`SENSOR_DELAY_NORMAL`	~200 ms	Screen rotation, step counter

6Accelerometer

The accelerometer measures acceleration forces on the device across three axes (X, Y, Z) in m/s². Uses include shake detection, step counting, tilt controls, and screen orientation.

Read accelerometer values

Kotlin — Display X, Y, Z valuesprivate fun handleAccelerometer(values: FloatArray) {
    val x = values[0]
    val y = values[1]
    val z = values[2]

    binding.tvAccel.text = String.format(
        Locale.getDefault(),
        "Accel — X: %.2f  Y: %.2f  Z: %.2f m/s²", x, y, z
    )
}

Shake detection

Kotlin — Detect device shakeclass ShakeDetector(private val onShake: () -> Unit) : SensorEventListener {

    private var lastUpdate = 0L
    private var lastX = 0f
    private var lastY = 0f
    private var lastZ = 0f
    private val shakeThreshold = 800f

    override fun onSensorChanged(event: SensorEvent) {
        if (event.sensor.type != Sensor.TYPE_ACCELEROMETER) return

        val currentTime = System.currentTimeMillis()
        if (currentTime - lastUpdate > 100) {
            val diffTime = currentTime - lastUpdate
            lastUpdate = currentTime

            val x = event.values[0]
            val y = event.values[1]
            val z = event.values[2]

            val speed = Math.abs(x + y + z - lastX - lastY - lastZ) / diffTime * 10000
            if (speed > shakeThreshold) onShake()

            lastX = x; lastY = y; lastZ = z
        }
    }

    override fun onAccuracyChanged(sensor: Sensor?, accuracy: Int) {}
}

Axis orientation

Phone held upright (portrait): X → right edge Y → top edge Z → out of screen (toward user) Flat on table: Z ≈ 9.8 m/s² (gravity) Free fall: all axes ≈ 0

7Gyroscope

The gyroscope measures angular rotation rate around X, Y, and Z axes in radians per second. It detects how fast the device is spinning — essential for AR, games, and camera stabilization.

Read gyroscope values

Kotlin — Display rotation ratesprivate fun handleGyroscope(values: FloatArray) {
    val x = values[0]  // pitch rate
    val y = values[1]  // yaw rate
    val z = values[2]  // roll rate

    binding.tvGyro.text = String.format(
        Locale.getDefault(),
        "Gyro — X: %.3f  Y: %.3f  Z: %.3f rad/s", x, y, z
    )
}

Rotation threshold alert

Kotlin — Detect fast rotationprivate var lastGyroAlert = 0L

private fun handleGyroscope(values: FloatArray) {
    val magnitude = sqrt(values[0] * values[0] + values[1] * values[1] + values[2] * values[2])
    binding.tvGyro.text = "Rotation rate: ${"%.3f".format(magnitude)} rad/s"

    if (magnitude > 2.0f && System.currentTimeMillis() - lastGyroAlert > 2000) {
        lastGyroAlert = System.currentTimeMillis()
        Toast.makeText(this, "Fast rotation detected!", Toast.LENGTH_SHORT).show()
    }
}

Accelerometer vs Gyroscope

Sensor	Measures	Unit	Example Use
Accelerometer	Linear acceleration + gravity	m/s²	Shake, tilt, steps
Gyroscope	Angular rotation speed	rad/s	AR, spin detection, games
Rotation Vector	Device orientation (fused)	quaternion	Compass, 3D UI

Best practice: Always unregister sensor listeners in onPause(). Use the lowest sensor delay that meets your needs. Combine accelerometer + gyroscope with a sensor fusion algorithm (or Sensor.TYPE_ROTATION_VECTOR) for smooth orientation tracking.

8Hands-On Exercises

1

Request location permission and display the device's last known GPS coordinates in a TextView using LocationManager.

2

Refactor to the Fused Location Provider with continuous updates. Show latitude, longitude, and accuracy updating every 5 seconds.

3

Build a CameraX preview screen with a live camera feed using PreviewView.

4

Add a capture button that saves a photo to app-specific external storage and shows a thumbnail.

5

Implement profile photo pick using the system TakePicture contract with FileProvider.

6

Register SensorManager listeners and display live accelerometer X/Y/Z values on screen.

7

Implement shake detection with the accelerometer — show a Toast when the user shakes the device.

8

Bonus: Display gyroscope rotation rates and alert when rotation exceeds a threshold.

Location, Camera & Sensors MCQ Practice

10 Basic MCQs 10 Advanced MCQs

10 Basic Location, Camera & Sensors MCQs

1

Fused Location Provider from?

ASQLite

BGoogle Play services Location API

CRoom only

DGradle

Explanation: FusedLocationProviderClient combines GPS, WiFi, cell for best fix.

2

GPS permission is?

AINTERNET only

BCAMERA only

CACCESS_FINE_LOCATION

DVIBRATE

Explanation: COARSE for approximate; FINE for precise GPS.

3

CameraX is?

ABluetooth stack

BSQL ORM

CNotification API

DJetpack camera library abstracting device cameras

Explanation: CameraX simplifies preview, capture, and lifecycle binding.

4

SensorManager provides access to?

ADevice sensors (accelerometer, gyroscope)

BSQLite only

CPlay Store

DGradle daemon

Explanation: Register SensorEventListener for sensor updates.

5

Accelerometer measures?

AOnly temperature

BLinear acceleration including gravity

CBattery level

DNetwork speed

Explanation: Used for shake detection, orientation helpers.

6

Gyroscope measures?

ASound level

BGPS latitude

CRotational rate around axes

DLight color only

Explanation: Angular velocity for rotation-aware features.

7

takePicture in CameraX uses?

ABroadcastReceiver

BMediaPlayer

CRoom DAO

DImageCapture use case

Explanation: ImageCapture.takePicture saves photo to file or MediaStore.

8

Location updates need?

ARuntime location permission + fused client request

BManifest only

CRoot

DEmulator only

Explanation: Also consider background location separate permission.

9

PreviewView in CameraX?

AShows notifications

BDisplays camera preview stream

CSQL table view

DMap widget

Explanation: Preview use case bound to lifecycle and PreviewView.

10

Sensor.TYPE_ACCELEROMETER constant identifies?

ACamera lens

BGPS provider

CAccelerometer hardware sensor

DWiFi radio

Explanation: Use getDefaultSensor(Sensor.TYPE_ACCELEROMETER).

10 Advanced Location, Camera & Sensors MCQs

11

ProcessCameraProvider.bindToLifecycle?

AStarts foreground service always

BBinds use cases to LifecycleOwner

CSQL migration

DGradle sync

Explanation: Auto unbinds when lifecycle destroyed — avoids camera leak.

12

Last location fast fetch?

ARequires root

BAlways blocks 30 sec

CgetLastLocation may return cached quick fix

DIllegal on API 34

Explanation: Useful for approximate start before continuous updates.

13

LocationRequest PRIORITY_HIGH_ACCURACY?

ANetwork banned

BNo GPS used

CBattery save only

DGPS preferred for best accuracy

Explanation: BALANCED_POWER_ACCURACY trades accuracy for battery.

14

Camera permission CAMERA is?

ADangerous runtime permission

BNormal automatic

CSignature only

DNot required

Explanation: Request before opening camera; handle denial gracefully.

15

Sensor delay SENSOR_DELAY_GAME?

AOnce per hour

BFastest reasonable rate for games

CMain thread only

DGPS interval

Explanation: UI, NORMAL, GAME, FASTEST rates for different use cases.

16

Geofencing uses?

ARoom database

BAccelerometer only

CLocation APIs + GeofencingClient

DToast

Explanation: Trigger events when entering/leaving geographic regions.

17

ImageAnalysis use case?

AGradle

BOnly storage

COnly audio

DFrame-by-frame analysis (ML, barcode)

Explanation: Analyzer receives ImageProxy for each frame.

18

Rotation vector sensor fuses?

AAccelerometer + magnetometer + gyro

BGPS only

CCamera only

DWiFi only

Explanation: Provides device orientation in space.

19

Background location on Android 10+?

ASame permission

BSeparate ACCESS_BACKGROUND_LOCATION after foreground

CAutomatic

DBanned entirely

Explanation: Strict Play Store review for background location justification.

20

Exif orientation on captured image?

ACameraX never sets

BAlways upright

CMay need rotation when displaying saved JPEG

DIllegal

Explanation: Read ExifInterface orientation and rotate bitmap if needed.

Click an option to select, then check answers.

Location, Camera & Sensors Interview Q&A

15 topic-focused questions for interviews and revision.

1Get current location with Fused Location Provider.medium

Answer: Check permission, fusedClient.getLastLocation or requestLocationUpdates with LocationCallback.

2CameraX basic setup.medium

Answer: ProcessCameraProvider.getInstance, bind Preview + ImageCapture to lifecycle, set PreviewView.

3Request location permission flow.easy

Answer: Declare in manifest, check ContextCompat.checkSelfPermission, request via ActivityResultContracts.

4Accelerometer shake detection idea.medium

Answer: Listen SENSOR_DELAY_UI, compute acceleration magnitude change threshold over time.

5Difference GPS vs Network location.easy

Answer: GPS satellite precise outdoors; network uses WiFi/cell faster indoors less precise.

6Why bind camera to lifecycle.medium

Answer: Automatically releases camera when Activity/Fragment destroyed — prevents lock and battery drain.

7Save photo to gallery.medium

Answer: ImageCapture OutputFileOptions with MediaStore content URI on Android 10+ scoped storage.

8Sensor registration and unregister.easy

Answer: sensorManager.registerListener in onResume, unregisterListener in onPause to save battery.

9Gyroscope use cases.medium

Answer: VR-like rotation, image stabilization hints, game controls.

10Location updates battery tips.hard

Answer: Use smallest interval needed, remove updates in onPause, use geofencing over constant polling.

11Handle permission denial for camera.easy

Answer: Show explanation, disable capture button, link to settings if permanent.

12CameraX vs old Camera API.medium

Answer: CameraX lifecycle-aware, device-agnostic, easier; Camera2 low-level control.

13Test sensors on emulator.easy

Answer: Extended controls send simulated location and sensor data.

14Foreground service for navigation.hard

Answer: Ongoing location in background often requires foreground service with location type.

15Privacy best practices for location.medium

Answer: Collect minimum needed, disclose in privacy policy, stop updates when not needed.

Location, Camera & Sensors

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