Camera access in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to request camera permission in an Android app.

Android Kotlin

ActivityCompat.requestPermissions(this, arrayOf([1]), 100)

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AManifest.permission.CAMERA

BManifest.permission.ACCESS_FINE_LOCATION

CManifest.permission.READ_CONTACTS

DManifest.permission.RECORD_AUDIO

Attempts:

3 left

💡 Hint

Common Mistakes

Using location or audio permissions instead of camera permission.

Forgetting to request permissions before accessing the camera.

To access the camera, you must request Manifest.permission.CAMERA.

2fill in blank

medium

Complete the code to check if camera permission is granted.

Android Kotlin

if (ContextCompat.checkSelfPermission(this, [1]) == PackageManager.PERMISSION_GRANTED) {
    // Permission granted
}

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AManifest.permission.ACCESS_FINE_LOCATION

BManifest.permission.READ_SMS

CManifest.permission.RECORD_AUDIO

DManifest.permission.CAMERA

Attempts:

3 left

💡 Hint

Common Mistakes

Checking wrong permission strings.

Not comparing the result to PackageManager.PERMISSION_GRANTED.

You check for Manifest.permission.CAMERA to see if camera access is allowed.

3fill in blank

hard

Fix the error in the code to open the camera using an Intent.

Android Kotlin

val cameraIntent = Intent([1])
startActivityForResult(cameraIntent, 101)

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AMediaStore.ACTION_IMAGE_CAPTURE

BIntent.ACTION_VIEW

CIntent.ACTION_SEND

DMediaStore.ACTION_VIDEO_CAPTURE

Attempts:

3 left

💡 Hint

Common Mistakes

Using ACTION_VIEW or ACTION_SEND which do not open the camera.

Using ACTION_VIDEO_CAPTURE when you want to take photos.

To open the camera for taking pictures, use MediaStore.ACTION_IMAGE_CAPTURE.

4fill in blank

hard

Fill both blanks to handle the camera permission result in onRequestPermissionsResult.

Android Kotlin

override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults)
    if (requestCode == [1]) {
        if (grantResults.isNotEmpty() && grantResults[0] == [2]) {
            // Permission granted
        }
    }
}

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A100

B101

CPackageManager.PERMISSION_GRANTED

DPackageManager.PERMISSION_DENIED

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong requestCode in the check.

Comparing grantResults to PERMISSION_DENIED instead of PERMISSION_GRANTED.

The requestCode should match the one used when requesting permission (100). The grant result should be compared to PackageManager.PERMISSION_GRANTED to check if permission was granted.

5fill in blank

hard

Fill all three blanks to create a camera preview using CameraX in a Fragment.

Android Kotlin

val cameraProviderFuture = ProcessCameraProvider.getInstance(requireContext())
cameraProviderFuture.addListener({
    val cameraProvider = cameraProviderFuture.get()
    val preview = Preview.Builder().build().also {
        it.setSurfaceProvider(viewFinder.[1])
    }
    val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
    try {
        cameraProvider.unbindAll()
        cameraProvider.bindToLifecycle(this, cameraSelector, preview, [2])
    } catch(exc: Exception) {
        Log.e("CameraX", "Use case binding failed", exc)
    }
}, ContextCompat.getMainExecutor(requireContext()))

val imageCapture = ImageCapture.Builder().build()

// Use imageCapture to take pictures

// The blank [3] should be the variable name for imageCapture

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AsurfaceProvider

BimageCapture

Cpreview

DcameraSelector

Attempts:

3 left

💡 Hint

Common Mistakes

Using preview instead of surfaceProvider for setSurfaceProvider.

Passing preview instead of imageCapture to bindToLifecycle.

Confusing variable names for imageCapture.

1. The preview's surface provider is set with surfaceProvider.
2. The imageCapture use case is passed to bindToLifecycle.
3. The variable imageCapture is used to take pictures.