[英]Turn on torch with MediaCapture on Windows Phone Silverlight 8.1
我的問題很簡單,我無法使用Windows Phone 8.1中的MediaCapture API打開閃光燈。 (我成功使用了8.0 API)
我用兩個按鈕構建了一個非常簡單的項目,一個按鈕切換FlashControl,另一個按鈕切換TorchControl。
沒有崩潰,也不例外。 我的手機支持FlashControl和TorchControl。 我也逐步調試,一切看起來都不錯,單擊按鈕時值會更改。
這是我的代碼:
MediaCapture m_captureManager;
public MainPage()
{
InitializeComponent();
}
private static async Task<DeviceInformation> GetCameraID(Windows.Devices.Enumeration.Panel desiredCamera)
{
DeviceInformation deviceID = (await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture))
.FirstOrDefault(x => x.EnclosureLocation != null && x.EnclosureLocation.Panel == desiredCamera);
if (deviceID != null) return deviceID;
else throw new Exception(string.Format("Camera {0} doesn't exist", desiredCamera));
}
protected async override void OnNavigatedTo(NavigationEventArgs e)
{
var cameraID = await GetCameraID(Windows.Devices.Enumeration.Panel.Back);
m_captureManager = new MediaCapture();
await m_captureManager.InitializeAsync(new MediaCaptureInitializationSettings
{
StreamingCaptureMode = StreamingCaptureMode.Video,
PhotoCaptureSource = PhotoCaptureSource.VideoPreview,
AudioDeviceId = string.Empty,
VideoDeviceId = cameraID.Id
});
}
private void button_ClickTorch(object sender, RoutedEventArgs e)
{
var torch = m_captureManager.VideoDeviceController.TorchControl;
if (torch.Supported)
{
if (torch.Enabled)
torch.Enabled = false;
else
torch.Enabled = true;
}
}
private void button_ClickFlash(object sender, RoutedEventArgs e)
{
if (captureManager.VideoDeviceController.FlashControl.Supported)
{
if (captureManager.VideoDeviceController.FlashControl.Enabled)
captureManager.VideoDeviceController.FlashControl.Enabled = false;
else
captureManager.VideoDeviceController.FlashControl.Enabled = true;
}
}
這是一段簡單的代碼,我無法使其正常工作……我非常絕望,所以我嘗試使用一個中間對象進行切換,如您所見,沒有但沒有改變結果(這是一致的) 。
我終於找到了問題所在。 為了能夠使用相機服務,我們必須開始預覽。 由於Silverlight無法使用CaptureElement,因此必須將CustomPreviewSink與VideoBrush一起使用
這是怎么做的(來自Microsoft doc )
private async void StartPreview()
{
previewSink = new Windows.Phone.Media.Capture.MediaCapturePreviewSink();
// List of supported video preview formats to be used by the default preview format selector.
var supportedVideoFormats = new List<string> { "nv12", "rgb32" };
// Find the supported preview format
var availableMediaStreamProperties = mediaCaptureManager.VideoDeviceController.GetAvailableMediaStreamProperties(
Windows.Media.Capture.MediaStreamType.VideoPreview)
.OfType<Windows.Media.MediaProperties.VideoEncodingProperties>()
.Where(p => p != null
&& !String.IsNullOrEmpty(p.Subtype)
&& supportedVideoFormats.Contains(p.Subtype.ToLower()))
.ToList();
var previewFormat = availableMediaStreamProperties.FirstOrDefault();
// Start Preview stream
await mediaCaptureManager.VideoDeviceController.SetMediaStreamPropertiesAsync(
Windows.Media.Capture.MediaStreamType.VideoPreview, previewFormat);
await mediaCaptureManager.StartPreviewToCustomSinkAsync(
new Windows.Media.MediaProperties.MediaEncodingProfile { Video = previewFormat }, previewSink);
// Set the source of the VideoBrush used for your preview
Microsoft.Devices.CameraVideoBrushExtensions.SetSource(viewfinderBrush, previewSink);
}
將這段代碼添加到以前的代碼中,它將起作用。 重要的是在更改任何參數之前先啟動預覽
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