Android-CameraX:在多个前置摄像头之间切换

Question

我正在尝试编写我的第一个 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)

并且代码基于官方的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

使用当前的 CameraX API，我认为您无法选择要使用的特定相机，您只能选择镜头朝向 ( CameraSelector.Builder().requireLensFacing(int) )，可以是正面或背面。当您绑定(bind)用例时，CameraX 会选择第一个满足用例要求的相机。例如，在将预览用例与启用或禁用扩展绑定(bind)时，可能会使用 2 个不同的后置摄像头。
CameraSelector API 似乎仍有增长空间，因此在 future ，您可能对选择哪个相机有更多的控制权。如果您现在需要这种控制，您可能需要使用 Camera2。