只需使用 CameraX 切换闪光灯

Question

对不起我的英语，我说得不好。

我有一个通过闪烁闪光灯与 arduino 设备通信的应用程序。我注意到 Camera1 和 Camera2 在所有 Android 设备上都存在问题，因此我构建了一个设置屏幕，用户可以测试两者并选择运行良好的一个。

我现在正在尝试与 CameraX 建立相同的通信，希望它适用于更多设备，但我找不到仅切换闪光灯的示例。我是android开发的新手，我找到的材料只是关于拍照之类的，但我什至不想打开相机屏幕，只需打开和关闭闪光灯，就像灯笼一样。

有人可以帮忙解决这个问题，或者发送一份有帮助的文档吗？

编辑1

我在 onCreate 中做了这个，我看到日志进入 logcat 但 flash 不切换。也许我需要创建案例？

lateinit var cameraControl: CameraControl
val cameraProcessFuture = ProcessCameraProvider.getInstance(this)
cameraProcessFuture.addListener(Runnable {
    val cameraProvider = cameraProcessFuture.get()

    val lifecycleOwner = this

    val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

    val camera = cameraProvider.bindToLifecycle(lifecycleOwner, cameraSelector)

    cameraControl = camera.cameraControl


    val listenableFuture = cameraControl!!.enableTorch(true)

    // cameraControl.enableTorch(false)
    Log.d("MurilloTesteCamera", "listener")
    listenableFuture.addListener(Runnable {

        Log.d("MurilloTesteCamera", "listener 2")
    }, ContextCompat.getMainExecutor(this))

}, ContextCompat.getMainExecutor(this))
Log.d("MurilloTesteCamera", "oncreate")

编辑2

这段代码我试图创建一个案例，但没有解决我的问题并且闪光灯仍然没有打开（我的活动实现了 CameraXConfig.Provider：

val context = this

Log.d("MurilloTesteCamera", "before initialize")
CameraX.initialize(context, cameraXConfig).addListener(Runnable {

    Log.d("MurilloTesteCamera", "inside initialize")


    CameraX.unbindAll()

    val preview = Preview.Builder()
        .apply {
            setTargetResolution(Size(640, 480))
        }
        .build()


    lateinit var cameraControl: CameraControl

    val cameraProcessFuture = ProcessCameraProvider.getInstance(context)
    cameraProcessFuture.addListener(Runnable {
        val cameraProvider = cameraProcessFuture.get()

        val lifecycleOwner = context

        val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

        val camera = cameraProvider.bindToLifecycle(lifecycleOwner, cameraSelector)

        cameraControl = camera.cameraControl

        camera.cameraInfo.hasFlashUnit()

        Log.d("MurilloTesteCamera", "info before -> " + camera.cameraInfo.torchState)
        Log.d("MurilloTesteCamera", "has flash -> " + camera.cameraInfo.hasFlashUnit())



        val listenableFuture = cameraControl.enableTorch(true)

        Log.d("MurilloTesteCamera", "listener")
        listenableFuture.addListener(Runnable {
            Log.d("MurilloTesteCamera", "info after -> " + camera.cameraInfo.torchState)

            Log.d("MurilloTesteCamera", "listener 2")
        }, ContextCompat.getMainExecutor(context))

        CameraX.bindToLifecycle(context, cameraSelector, preview)

    }, ContextCompat.getMainExecutor(context))



}, ContextCompat.getMainExecutor(context))

Log.d("MurilloTesteCamera", "after initialize")
while (!CameraX.isInitialized()){}
Log.d("MurilloTesteCamera", "after while")

Answer 1

在 CameraX 中，用于打开/关闭相机手电筒的 API 是CameraControl.enableTorch(boolean). 要获取CameraControl实例，您可以按照文档进行操作：

应用程序可以通过 Camera.getCameraControl() 检索 CameraControl 实例。CameraControl 准备好在检索到 Camera 并将 UseCases 绑定到该相机后立即开始操作

这意味着您需要首先将一个用例（或多个用例）绑定到一个生命周期。你提到你不想open a camera screen，所以我假设你的意思是你不想绑定任何用例，在这种情况下你可以bindToLifecycle()用零用例调用。这可能适用于最新版本的 CameraX，也可能不适用。

总而言之，你必须写这样的东西：

val cameraProcessFuture = ProcessCameraProvider.getInstance(context)
cameraProcessFuture.addListener(Runnable {
    val cameraProvider = cameraProcessFuture.get()

    // Choose the lifecycle to which the camera will be attached to
    val lifecycleOwner = /* Can be an Activity, Fragment, or a custom lifecycleOwner */

    // Choose a valid camera the device has
    val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

    // You might need to create a use case to start capture requests 
    // with the camera
    val imageAnalysis = ImageAnalysis.Builder()
          .build()
          .apply {
              val executor = /* Define an executor */
              setAnalyzer(executor, ImageAnalysis.Analyzer {
                  it.close()
              })
           }

    // Get a camera instance
    val camera = cameraProvider.bindToLifecycle(lifecycleOwner, cameraSelector)

    // Get a cameraControl instance
    val cameraControl = camera.cameraControl

    // Call enableTorch(), you can listen to the result to check whether it was successful
    cameraControl.enableTorch(true) // enable torch
    cameraControl.enableTorch(false) // disbale torch
}, ContextCompat.getMainExecutor(context))