Android-CameraX：在多个前置摄像头之间切换

Question

我\xc2\xb4m 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）

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

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相关代码：

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/** Declare and bind preview, capture and analysis use cases */\nprivate fun bindCameraUseCases() {\n\n    // Get screen metrics used to setup camera for full screen resolution\n    val metrics = DisplayMetrics().also { viewFinder.display.getRealMetrics(it) }\n    Log.d(TAG, "Screen metrics: ${metrics.widthPixels} x ${metrics.heightPixels}")\n\n    val screenAspectRatio = aspectRatio(metrics.widthPixels, metrics.heightPixels)\n    Log.d(TAG, "Preview aspect ratio: $screenAspectRatio")\n\n    val rotation = viewFinder.display.rotation\n\n    // Bind the CameraProvider to the LifeCycleOwner\n\n    val cameraSelector = CameraSelector.Builder().requireLensFacing(lensFacing).build()\n\n    val cameraProviderFuture = ProcessCameraProvider.getInstance(requireContext())\n    cameraProviderFuture.addListener(Runnable {\n\n        // CameraProvider\n        val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()\n\n        // Preview\n        preview = Preview.Builder()\n            // We request aspect ratio but no resolution\n            .setTargetAspectRatio(screenAspectRatio)\n            // Set initial target rotation\n            .setTargetRotation(rotation)\n            .build()\n\n        // ImageCapture\n        imageCapture = ImageCapture.Builder()\n            .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)\n            // We request aspect ratio but no resolution to match preview config, but letting\n            // CameraX optimize for whatever specific resolution best fits our use cases\n            .setTargetAspectRatio(screenAspectRatio)\n            // Set initial target rotation, we will have to call this again if rotation changes\n            // during the lifecycle of this use case\n            .setTargetRotation(rotation)\n            .build()\n\n        // Must unbind the use-cases before rebinding them\n        cameraProvider.unbindAll()\n\n        try {\n            // A variable number of use-cases can be passed here -\n            // camera provides access to CameraControl & CameraInfo\n            camera = cameraProvider.bindToLifecycle(\n                    this, cameraSelector, preview, imageCapture /**, imageAnalyzer*/)\n\n            // Attach the viewfinder\'s surface provider to preview use case\n            preview?.setSurfaceProvider(viewFinder.createSurfaceProvider(camera?.cameraInfo))\n        } catch(exc: Exception) {\n            Log.e(TAG, "Use case binding failed", exc)\n        }\n\n    }, ContextCompat.getMainExecutor(requireContext()))\n}\n

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Answer 1

使用当前的 CameraX API，我认为您无法选择使用哪个特定相机，您只能选择镜头朝向（CameraSelector.Builder().requireLensFacing(int)），可以是正面或背面。当您绑定用例时，CameraX 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的扩展绑定时，可以使用 2 个不同的后置摄像头。

该CameraSelectorAPI 似乎仍有增长空间，因此将来您可能可以更好地控制选择哪个相机。如果您现在需要这种控制，您可能需要使用 Camera2。