Camera2 Extension

[Muhannad508]

I'd like to propose an extension to get a camera by direction. the implementation would be something like that :

enum class FACING(val direction: Int) {
    FRONT_CAMERA(CameraCharacteristics.LENS_FACING_FRONT), REAR_CAMERA(CameraCharacteristics.LENS_FACING_BACK)
}

@RequiresApi(21)
fun CameraManager.getCameraByDirection(direction: FACING): Pair<String, CameraCharacteristics> {

    for (cameraId in this.cameraIdList) {
        val characteristics = this.getCameraCharacteristics(cameraId)

        val cameraDirection = characteristics.get(CameraCharacteristics.LENS_FACING)
        if (cameraDirection != null && cameraDirection == direction.direction) {
            return Pair(cameraId, characteristics)
        }
    }
    throw RuntimeException("Camera Not Found")
}

Usage :

val manager = context.getSystemService(Context.CAMERA_SERVICE) as CameraManager
 val (cameraId, cameraCharacteristics) = manager.getCameraByDirection(REAR_CAMERA)

[kioba]

As far as I know, there could be multiple LENS_FACING and LENS_FACING_BACK hardware but we always return the first one. we have to also take LENS_FACING_EXTERNAL into consideration https://developer.android.com/reference/android/hardware/camera2/CameraMetadata.html#LENS_FACING_EXTERNAL

The Pair return types indicate that we are doing too many at once.

I would suggest separating the implementation into two part.

1. Get all the Characteristics and return them as a Sequence.

fun CameraManager.getCameraCharacteristics() : Sequence<CameraCharacteristics> =
  cameraIdList.asSequence().map{ getCameraCharacteristics(cameraId) }

Now anyone can use their own algorithm to find the best fitting camera for their usecase. And because Sequence is lazy evaluated it cost less to find the right element.

2. Extend CameraCharacteristics with is* and isNot* properties. just one example:

val CameraCharacteristics.isFrontCamera: Boolean
    get() {
        val cameraDirection = get(CameraCharacteristics.LENS_FACING)
        return cameraDirection != null && cameraDirection == LENS_FACING_FRONT
    }

[Muhannad508]

Thanks @kioba for your inputs . But it seems hardware APIs go beyond the scope of android-ktx . as stated in the below link : #373

[kioba]

@Muhannad508 thanks for the link! That is good to know 👍