Choosing the Right Camera Library
Android provides multiple camera libraries:
- CameraX: Modern, lifecycle-aware, and easy to use.
- Camera2: Flexible but requires more setup.
- Camera: Deprecated and not recommended for new projects.
Key Components of CameraX
| Component | Description |
|---|---|
| CameraProvider | Manages camera connections and lifecycle binding. |
| UseCase | Represents camera features like Preview, ImageCapture, VideoCapture, and ImageAnalysis. |
| Lifecycle-Aware | Automatically handles camera resources based on lifecycle events. |
Use Cases
a. Preview: Display the Camera Feed
val preview = Preview.Builder().build().also {
it.setSurfaceProvider(viewFinder.surfaceProvider)
}
b. ImageCapture: Capture Still Images
val imageCapture = ImageCapture.Builder()
.setTargetRotation(Surface.ROTATION_0)
.setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
.build()
imageCapture.takePicture(
outputFileOptions,
ContextCompat.getMainExecutor(context),
object : ImageCapture.OnImageSavedCallback {
override fun onImageSaved(outputFileResults: ImageCapture.OutputFileResults) {
// Handle successful image capture
}
override fun onError(exception: ImageCaptureException) {
// Handle error
}
}
)
c. VideoCapture: Record Videos
val videoCapture = VideoCapture.Builder().build()
videoCapture.startRecording(
outputFileOptions,
ContextCompat.getMainExecutor(context),
object : VideoCapture.OnVideoSavedCallback {
override fun onVideoSaved(outputFileResults: VideoCapture.OutputFileResults) {
// Handle successful video capture
}
override fun onError(videoCaptureError: Int, message: String, cause: Throwable?) {
// Handle error
}
}
)
d. ImageAnalysis: Analyze Camera Frames
val imageAnalysis = ImageAnalysis.Builder().build().also {
it.setAnalyzer(ContextCompat.getMainExecutor(context), YourImageAnalyzer())
}
class YourImageAnalyzer : ImageAnalysis.Analyzer {
override fun analyze(image: ImageProxy) {
// Process the image frame
image.close() // Don't forget to close the image
}
}
Camera Initialization
val cameraProviderFuture = ProcessCameraProvider.getInstance(context)
cameraProviderFuture.addListener({
val cameraProvider = cameraProviderFuture.get()
// Bind use cases to lifecycle
cameraProvider.bindToLifecycle(
lifecycleOwner,
CameraSelector.DEFAULT_BACK_CAMERA,
preview,
imageCapture,
videoCapture,
imageAnalysis
)
}, ContextCompat.getMainExecutor(context))
Switching Cameras
val newCameraSelector = CameraSelector.DEFAULT_FRONT_CAMERA
cameraProvider.unbindAll()
cameraProvider.bindToLifecycle(this, newCameraSelector, preview, imageCapture)
Face Detection with ML Kit
val faceDetector = FaceDetection.getClient(
FaceDetectorOptions.Builder()
.setPerformanceMode(FaceDetectorOptions.PERFORMANCE_MODE_FAST)
.setLandmarkMode(FaceDetectorOptions.LANDMARK_MODE_ALL)
.build()
)
imageAnalysis.setAnalyzer(ContextCompat.getMainExecutor(context), { imageProxy ->
val mediaImage = imageProxy.image ?: return@setAnalyzer
val rotationDegrees = imageProxy.imageInfo.rotationDegrees
val inputImage = InputImage.fromMediaImage(mediaImage, rotationDegrees)
faceDetector.process(inputImage)
.addOnSuccessListener { faces ->
// Process detected faces
for (face in faces) {
// Handle each face
}
}
.addOnFailureListener { e ->
// Handle error
}
.addOnCompleteListener {
imageProxy.close() // Close the image proxy
}
})
Camera Permissions
Ensure you handle camera permissions in your app. Use ActivityCompat.requestPermissions to request permissions at runtime.
CameraX vs CameraProvider Comparison
| Feature | CameraController | CameraProvider |
|---|---|---|
| Lifecycle | Manages camera lifecycle automatically | Requires manual binding to lifecycle |
| Use Cases | Supports Preview, ImageCapture, VideoCapture, ImageAnalysis | Supports Preview, ImageCapture, VideoCapture, ImageAnalysis |
| Camera Selection | Simplified camera selection | Uses CameraSelector for camera selection |
| Configuration | Provides a simple API for configuration | More flexible but requires more setup |
| Threading | Uses main thread for callbacks | Allows custom executor for callbacks |
| Error Handling | Built-in error handling | Requires custom error handling |
| Face Detection | Built-in support for face detection | Requires additional libraries (e.g., ML Kit) |
| Camera Switching | Simplified camera switching | Requires unbinding and rebinding |
| Performance | Optimized for common use cases | More flexible but may require optimization |
| Dependencies | Minimal dependencies | Requires CameraX and related libraries |
| Use Case Binding | Automatically binds use cases | Requires manual binding of use cases |
| Camera Control | Provides camera control methods | Requires CameraControl for advanced control |
| Image Capture | Simplified image capture API | More flexible but requires more setup |
| Video Capture | Simplified video capture API | More flexible but requires more setup |
| Image Analysis | Simplified image analysis API | More flexible but requires more setup |
| Camera Permissions | Handles camera permissions automatically | Requires manual permission handling |
| Architecture | Follows CameraX architecture | Follows CameraX architecture |
| Surface | PreviewView | Custom Surface |
For more details, refer to the CameraX Architecture.