在Windows 8.1商店应用程序中找不到Front，Back Camera

Question

我已经开发了Windows 8.1商店应用程序，它需要通过使用后置摄像头和帖子来捕获照片。

MediaCaptureInitializationSettings _captureSettings = new var devices = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);
    foreach (var device in devices)
    {
    if (device.EnclosureLocation != null && device.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Back)
                        {
                            deviceId = device.Id;
                            break;
                        }
                    }
  if (!string.IsNullOrEmpty(deviceId))
                    {
                        _captureSettings.AudioDeviceId = "";
                        _captureSettings.VideoDeviceId = deviceId;
                        _captureSettings.PhotoCaptureSource = Windows.Media.Capture.PhotoCaptureSource.Photo;
                        _captureSettings.StreamingCaptureMode = Windows.Media.Capture.StreamingCaptureMode.Video;
                    }
captureManager = new MediaCapture();
await captureManager.InitializeAsync(_captureSettings);
                    await captureManager.ClearEffectsAsync(MediaStreamType.Photo);
                    capturePreview1.Source = captureManager;
                    await captureManager.StartPreviewAsync();
</code>

Here i am getting two devices but that devices EnclosureLocation is null, so i can't find which one is front and back camera.

so have decided to get second device from list 

<code>
deviceId = devices[1].Id;
</code>

but it throws an error like "The current capture source does not have an independent photo stream."
in the line of initializing MediaCapture

<code>

await captureManager.InitializeAsync(_captureSettings);

</code>

我试过windows surface pro 2和acer设备。 请指教。 提前致谢。

Answer 1

尝试更好地组织代码，你在同一行上有两个等号，你的代码编写得不好，所以很难阅读。

要在Windows 8.1停止应用程序中使用相机，我使用此代码：

// First need to find all webcams
DeviceInformationCollection webcamList = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture)

// Then I do a query to find the front webcam
DeviceInformation frontWebcam = (from webcam in webcamList
 where webcam.EnclosureLocation != null 
 && webcam.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Front
 select webcam).FirstOrDefault();

// Same for the back webcam
DeviceInformation backWebcam = (from webcam in webcamList
 where webcam.EnclosureLocation != null 
 && webcam.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Back
 select webcam).FirstOrDefault();

// Then you need to initialize your MediaCapture
var captureManager = new MediaCapture();
await captureManager.InitializeAsync(new MediaCaptureInitializationSettings
{
    // Choose the webcam you want (backWebcam or frontWebcam)
    VideoDeviceId = backWebcam.Id,
    AudioDeviceId = "",
    StreamingCaptureMode = StreamingCaptureMode.Video,
    PhotoCaptureSource = PhotoCaptureSource.VideoPreview
});

// Set the source of the CaptureElement to your MediaCapture
capturePreview1.Source = captureManager;

// Start the preview
await captureManager.StartPreviewAsync();

这样它更容易阅读。 代码差别不大，MediaCaptureInitializationSettings也不一样。

此代码适用于Surface 2 RT和Nokia 635，因此它适用于您。

编辑：

似乎它适用于使用Windows RT的设备，但在完整的Windows 8.1设备上，它始终为空。 Msdn说：

如果没有可用的机箱位置信息，则该属性将为null

所以你能做的就是首先尝试看看你是否找到了backwebcam，如果它是null，那就拿最后一个;

DeviceInformation backWebcam = (from webcam in webcamList
 where webcam.EnclosureLocation != null 
 && webcam.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Back
 select webcam).FirstOrDefault();

if (backWebcam == null)
{
   backWebcam = webcamList.Last();
}

但是你不确定该系列中的最后一个是后一个，所以你应该添加一个按钮让用户切换相机

如果更换相机，

await captureManager.StopPreviewAsync();

await captureManager.InitializeAsync(new MediaCaptureInitializationSettings
    {
        // Choose an other webcam 
        VideoDeviceId = //id of the new webcam,
        AudioDeviceId = "",
        StreamingCaptureMode = StreamingCaptureMode.Video,
        PhotoCaptureSource = PhotoCaptureSource.VideoPreview
    });

 await captureManager.StartPreviewAsync();

通过这种方式你可以确定用户可以选择合适的相机，即使你是programmaticaly无法分辨哪一个是哪个