安卓开发：CameraX无法识别USB UVC摄像头，如何解决？

以下是针对你的问题的具体解决步骤：

• 确认CameraX依赖版本
  CameraX对USB摄像头（UVC设备）的支持依赖较新版本，确保你的build.gradle中使用至少1.2.0及以上的CameraX库，同时引入camera2扩展：

  dependencies {
    def camerax_version = "1.3.0"
    implementation "androidx.camera:camera-core:$camerax_version"
    implementation "androidx.camera:camera-camera2:$camerax_version"
    implementation "androidx.camera:camera-lifecycle:$camerax_version"
    implementation "androidx.camera:camera-view:$camerax_version"
  }
  

• 申请并处理USB权限
  除常规的CAMERA权限，还需获取USB设备访问权限：

  1. 在AndroidManifest.xml中添加权限声明：

     <uses-permission android:name="android.permission.CAMERA" />
     <uses-permission android:name="android.permission.USB_PERMISSION" />
     <uses-feature android:name="android.hardware.usb.host" />
     

  2. 动态请求USB权限，获取目标UsbDevice后发起权限申请：

     val usbManager = getSystemService(Context.USB_SERVICE) as UsbManager
     val targetDevice: UsbDevice = // 从UsbManager枚举到的USB摄像头设备
     val permissionIntent = PendingIntent.getBroadcast(this, 0, Intent(ACTION_USB_PERMISSION), PendingIntent.FLAG_IMMUTABLE)
     usbManager.requestPermission(targetDevice, permissionIntent)
     

  3. 通过BroadcastReceiver接收权限结果，只有获取权限后，CameraX才可能识别该设备。

• 主动枚举并绑定USB摄像头
  部分场景下CameraX不会自动枚举USB摄像头，可手动遍历可用设备并绑定：

  val cameraProviderFuture = ProcessCameraProvider.getInstance(this)
  cameraProviderFuture.addListener({
    val cameraProvider = cameraProviderFuture.get()
    // 遍历所有可用摄像头信息
    for (cameraInfo in cameraProvider.availableCameraInfos) {
      val characteristics = cameraInfo.cameraCharacteristics
      // 判断是否为外部USB摄像头
      val isExternalCamera = characteristics.get(CameraCharacteristics.EXTERNAL_CAMERA) == true
                              || characteristics.get(CameraCharacteristics.LENS_FACING) == null
      if (isExternalCamera) {
        // 绑定预览功能
        val preview = Preview.Builder().build().also {
          it.setSurfaceProvider(previewView.surfaceProvider)
        }
        try {
          cameraProvider.unbindAll()
          cameraProvider.bindToLifecycle(this as LifecycleOwner, CameraSelector.fromCameraInfo(cameraInfo), preview)
        } catch (e: Exception) {
          // 处理绑定异常
        }
      }
    }
  }, ContextCompat.getMainExecutor(this))
  

• 检查设备Camera2支持级别
  USB摄像头需要设备支持至少Camera2的LEGACY级别，可通过以下代码验证：

  val cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager
  for (cameraId in cameraManager.cameraIdList) {
    val characteristics = cameraManager.getCameraCharacteristics(cameraId)
    val supportLevel = characteristics.get(CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL)
    if (supportLevel != null && supportLevel >= CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY) {
      // 设备支持符合要求的Camera2级别
    }
  }
  

内容的提问来源于stack exchange，提问作者IdH