Android CameraX：在多个前置摄像头之间切换

Question

我试图写我的第一个Android相机应用程序，但它总是选择变焦相机而不是主相机。（我在华为P30 Pro上测试过）

代码基于官方的camerax示例应用程序(https://github.com/android/camera-samples/tree/master/CameraXBasic)

相关代码：

/** Declare and bind preview, capture and analysis use cases */
private fun bindCameraUseCases() {

    // Get screen metrics used to setup camera for full screen resolution
    val metrics = DisplayMetrics().also { viewFinder.display.getRealMetrics(it) }
    Log.d(TAG, "Screen metrics: ${metrics.widthPixels} x ${metrics.heightPixels}")

    val screenAspectRatio = aspectRatio(metrics.widthPixels, metrics.heightPixels)
    Log.d(TAG, "Preview aspect ratio: $screenAspectRatio")

    val rotation = viewFinder.display.rotation

    // Bind the CameraProvider to the LifeCycleOwner

    val cameraSelector = CameraSelector.Builder().requireLensFacing(lensFacing).build()

    val cameraProviderFuture = ProcessCameraProvider.getInstance(requireContext())
    cameraProviderFuture.addListener(Runnable {

        // CameraProvider
        val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()

        // Preview
        preview = Preview.Builder()
            // We request aspect ratio but no resolution
            .setTargetAspectRatio(screenAspectRatio)
            // Set initial target rotation
            .setTargetRotation(rotation)
            .build()

        // ImageCapture
        imageCapture = ImageCapture.Builder()
            .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
            // We request aspect ratio but no resolution to match preview config, but letting
            // CameraX optimize for whatever specific resolution best fits our use cases
            .setTargetAspectRatio(screenAspectRatio)
            // Set initial target rotation, we will have to call this again if rotation changes
            // during the lifecycle of this use case
            .setTargetRotation(rotation)
            .build()

        // Must unbind the use-cases before rebinding them
        cameraProvider.unbindAll()

        try {
            // A variable number of use-cases can be passed here -
            // camera provides access to CameraControl & CameraInfo
            camera = cameraProvider.bindToLifecycle(
                    this, cameraSelector, preview, imageCapture /**, imageAnalyzer*/)

            // Attach the viewfinder's surface provider to preview use case
            preview?.setSurfaceProvider(viewFinder.createSurfaceProvider(camera?.cameraInfo))
        } catch(exc: Exception) {
            Log.e(TAG, "Use case binding failed", exc)
        }

    }, ContextCompat.getMainExecutor(requireContext()))
}

Answer 1

我有一个类似的问题，但与后摄像头。我检查了一些设备，发现在我所有测试的设备上，我都可以选择摄像头id并获得正确的摄像头：

• 摄像头ID“0”-

所以我创建了一个自定义的相机过滤器，我过滤相机id"0"：

class CameraIdFilter(private val cameraId: String) : CameraFilter {

override fun filterCameras(cameras: Set<CameraInternal>): Set<CameraInternal> {
    val resultCameras: MutableSet<CameraInternal> = LinkedHashSet()
    for (camera in cameras) {
        val cameraId = camera.cameraInfoInternal.cameraId
        if (cameraId == this.cameraId) {
            resultCameras.add(camera)
        }
    }
    return resultCameras
}

}

并将过滤器附加到摄影机选择器：

        val cameraSelectorBuilder = CameraSelector.Builder()
            .requireLensFacing(lensFacing)
            .appendFilter(CameraIdFilter("0"))

我不建议在生产应用程序中使用此功能，因为我确信有些设备不遵循此约定/模式。但您可以将其用于内部应用程序，以便了解用户使用的设备

Answer 2

在当前的CameraX API中，我认为您无法选择要使用的特定相机，您只能选择面向镜头的（CameraSelector.Builder（）。RequiremensFacing（int）），可以是正面也可以是背面。绑定用例时，CameraX会选择第一个满足用例要求的摄影机。例如，当绑定启用扩展与禁用扩展的预览用例时，可能会使用两个不同的后摄像头。

CameraSelectorAPI似乎仍有增长空间，因此在未来，您可能会对选择哪个摄像头有更多的控制权。如果您现在需要这种控制，您可能需要使用Camera2。