UWP MediaCapture FocusAsync：操作无效

Question

我使用 MediapCapture 扫描二维码。这是我的配置：

var cameras = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);
int cameraIndex = cameras.Count > 1 ? 1 : 0;
MediaCaptureInitializationSettings settings = new MediaCaptureInitializationSettings { VideoDeviceId = cameras[cameraIndex].Id };
settings.StreamingCaptureMode = StreamingCaptureMode.Video;

await _mediaCapture.InitializeAsync();
SetResolution();
_mediaCapture.SetPreviewRotation(VideoRotation.Clockwise90Degrees);
_mediaCapture.VideoDeviceController.FocusControl.Configure(new Windows.Media.Devices.FocusSettings() { Mode = Windows.Media.Devices.FocusMode.Auto });
videoCapture.Source = _mediaCapture;
await _mediaCapture.StartPreviewAsync();

我的 CaptureElement 上还有一个调用 FocusAsync 方法的 Tapped 事件：

await _mediaCapture.VideoDeviceController.FocusControl.FocusAsync();

我的问题是当我尝试集中注意力时有时（并非总是）出现错误（即使这是我第一次调用它）。这个错误是：

The op is invalid

编辑：

这是我的堆栈跟踪：（没有内部异常）

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter.GetResult() at ProjectName.Views.QrCodeScannerPage.d__8.MoveNext()

Answer 1

最后我从以下例子中选择设置自动对焦： https://msdn.microsoft.com/en-us/windows/uwp/audio-video-camera/capture-device-controls-for-photo-and-video-capture

UWP MediaCapture FocusAsync：操作无效

UWP MediaCapture FocusAsync: the op is invalid

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