Camera access in Android Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What permission is required to access the camera on Android?

The android.permission.CAMERA permission must be declared in the AndroidManifest.xml file and requested at runtime for Android 6.0 and above.

beginner

How do you launch the camera app to take a photo using an Intent in Kotlin?

Use an Intent with action MediaStore.ACTION_IMAGE_CAPTURE and start it with startActivityForResult or the modern registerForActivityResult API.

intermediate

What is the purpose of registerForActivityResult in camera access?

It replaces startActivityForResult to handle the result of the camera app in a cleaner, lifecycle-aware way.

intermediate

Why do you need to create a file URI before launching the camera Intent?

To save the captured photo, you provide a file URI where the camera app stores the image. This avoids getting only a thumbnail and allows full-size photo saving.

advanced

What is the role of FileProvider in camera access?

FileProvider securely shares file URIs with other apps, like the camera app, avoiding exposing file paths directly.

Which permission must be requested at runtime to use the camera on Android 6.0+?

A android.permission.CAMERA

B android.permission.INTERNET

C android.permission.ACCESS_FINE_LOCATION

D android.permission.READ_CONTACTS

The CAMERA permission is required to access the device camera and must be requested at runtime starting from Android 6.0.

What Intent action is used to open the camera app for capturing a photo?

A Intent.ACTION_SEND

B Intent.ACTION_VIEW

C MediaStore.ACTION_IMAGE_CAPTURE

D MediaStore.ACTION_VIDEO_CAPTURE

MediaStore.ACTION_IMAGE_CAPTURE launches the camera app to take a photo.

Which API is recommended for receiving results from the camera Intent in modern Android development?

A startActivityForResult

B onActivityResult

C startService

D registerForActivityResult

registerForActivityResult is the modern, lifecycle-aware API to handle activity results.

Why is FileProvider used when sharing a photo file URI with the camera app?

A To compress the image

B To securely share file URIs without exposing file paths

C To encrypt the photo

D To upload the photo to cloud

FileProvider securely shares file URIs with other apps, preventing direct file path exposure.

What happens if you do not provide a file URI when launching the camera Intent?

A You get only a small thumbnail image

B The camera app records video instead

C The photo is saved automatically in gallery

D The camera app crashes

Without a file URI, the camera returns only a small thumbnail image in the Intent result.

Explain the steps to capture a photo using the camera in an Android app with Kotlin.

Think about permissions, file storage, Intent, and result handling.

Describe why FileProvider is important when working with camera photo files on Android.

Consider Android's file access security model.

Practice

1. What is the main purpose of using MediaStore.ACTION_IMAGE_CAPTURE in an Android app?

easy

A. To open the device camera to take a photo

B. To open the device gallery to select a photo

C. To record audio using the microphone

D. To access device location services

Solution

1. Step 1: Understand the intent action

   MediaStore.ACTION_IMAGE_CAPTURE is a predefined intent action to launch the camera app for capturing images.

2. Step 2: Identify the purpose in the app

   This intent opens the camera so the user can take a photo, which the app can then receive.

3. Final Answer:

   To open the device camera to take a photo -> Option A

4. Quick Check:

   Camera intent = open camera [OK]

Hint: Remember: ACTION_IMAGE_CAPTURE means open camera [OK]

Common Mistakes:

• Confusing camera intent with gallery intent
• Thinking it records audio
• Assuming it accesses location

2. Which of the following is the correct Kotlin syntax to start the camera intent for result in an Activity?

easy

A. startActivityForResult(Intent(MediaStore.ACTION_IMAGE_CAPTURE), REQUEST_CODE)

B. startActivity(Intent(MediaStore.ACTION_IMAGE_CAPTURE))

C. startActivityForResult(MediaStore.ACTION_IMAGE_CAPTURE, REQUEST_CODE)

D. startActivityForResult(Intent(REQUEST_CODE), MediaStore.ACTION_IMAGE_CAPTURE)

Solution

1. Step 1: Check the method signature

   startActivityForResult requires an Intent and a request code integer.

2. Step 2: Verify the Intent creation

   The Intent must be created with MediaStore.ACTION_IMAGE_CAPTURE as the action.

3. Final Answer:

   startActivityForResult(Intent(MediaStore.ACTION_IMAGE_CAPTURE), REQUEST_CODE) -> Option A

4. Quick Check:

   Intent + request code = startActivityForResult [OK]

Hint: Intent first, then request code in startActivityForResult [OK]

Common Mistakes:

• Passing action string instead of Intent
• Omitting request code
• Swapping Intent and request code parameters

3. Given this code snippet in an Activity, what will be the output when the user takes a photo successfully?

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
  super.onActivityResult(requestCode, resultCode, data)
  if (requestCode == REQUEST_CODE && resultCode == RESULT_OK) {
    val photo = data?.extras?.get("data") as Bitmap
    imageView.setImageBitmap(photo)
  }
}

medium

A. The app will display a default image instead

B. The app will crash due to a null pointer exception

C. Nothing happens because onActivityResult is not called

D. The photo taken by the user will be displayed in imageView

Solution

1. Step 1: Understand onActivityResult behavior

   This method receives the result from the camera intent when the user takes a photo.

2. Step 2: Check the code logic

   If the request and result codes match, it extracts the photo bitmap from the intent extras and sets it to the imageView.

3. Final Answer:

   The photo taken by the user will be displayed in imageView -> Option D

4. Quick Check:

   Photo bitmap set to imageView = display photo [OK]

Hint: Check requestCode and resultCode before using data [OK]

Common Mistakes:

• Not checking requestCode or resultCode
• Casting data extras incorrectly
• Forgetting to call super.onActivityResult

4. Identify the error in this Kotlin code snippet for launching the camera:

val intent = Intent()
intent.action = MediaStore.ACTION_IMAGE_CAPTURE
startActivityForResult(intent)

medium

A. Intent action should be set using setAction() method

B. Missing request code parameter in startActivityForResult

C. Intent should be created with MediaStore.ACTION_IMAGE_CAPTURE in constructor

D. startActivityForResult cannot be used to launch camera

Solution

1. Step 1: Check startActivityForResult usage

   This method requires two parameters: an Intent and a request code integer.

2. Step 2: Identify missing parameter

   The code calls startActivityForResult with only the Intent, missing the request code.

3. Final Answer:

   Missing request code parameter in startActivityForResult -> Option B

4. Quick Check:

   startActivityForResult needs Intent + request code [OK]

Hint: Always pass request code with Intent in startActivityForResult [OK]

Common Mistakes:

• Omitting request code parameter
• Using wrong Intent constructor
• Misunderstanding startActivityForResult signature

5. You want to save a full-size photo taken by the camera to a file in your app. Which approach correctly combines camera intent and file handling in Kotlin?

hard

A. Save photo by reading camera app cache directory after intent finishes

B. Start camera intent without extras, then save thumbnail from data extras

C. Create a file URI, pass it with Intent extra MediaStore.EXTRA_OUTPUT, then start camera intent

D. Use MediaStore.ACTION_VIDEO_CAPTURE intent to save photo file

Solution

1. Step 1: Understand full-size photo saving

   To save a full-size photo, you must provide a file URI where the camera app saves the image.

2. Step 2: Use Intent extra MediaStore.EXTRA_OUTPUT

   Pass the file URI as an extra in the camera intent using MediaStore.EXTRA_OUTPUT before starting the intent.

3. Step 3: Start camera intent with this setup

   This ensures the camera saves the full photo to your file, not just a thumbnail in data extras.

4. Final Answer:

   Create a file URI, pass it with Intent extra MediaStore.EXTRA_OUTPUT, then start camera intent -> Option C

5. Quick Check:

   File URI + EXTRA_OUTPUT = full photo saved [OK]

Hint: Use EXTRA_OUTPUT with file URI for full-size photos [OK]

Common Mistakes:

• Relying on thumbnail from data extras only
• Not providing file URI to camera intent
• Using video capture intent for photos