My CaptureElements are showing strange behavior. When I set a instantiated MediaCapture as the CaptureElements Source and then call MediaCapture.StartPreviewAsync() the CaptureElement doesn't show anything.
I have one Application (main-app) with a functional BarcodeScanner on the LoginPage. -> Works!
Then I wanted to copy the same code to the SettingsPage with small modifications so in case of several attached cameras, the default one can be set. -> Doesn't work
Then I tried to run the main-app with the help of the remote debugger on other windows tablets with same Windows 10 Version as my machine (keep in mind, that the BarcodeScanner on the Login-Screen works on my machine). -> doesn't work
Because of these failures I copied the running code from the main-apps LoginPage to a completely new solution (lets call it test-app) with the same settings as the original one. I even experimented with referencing the same Dlls, implementing the same design pattern etc. -> doesn't work
My Machine: Win 10 Pro Version 1809 Build 17763.652
DevEnv: MS Visual Studio 2019 Pro Vers. 16.1.6
EDIT: As minimum required Windows Version I selected Build 16229 and my target Version is Build 17763 (my systems Win version)
The "Allow apps to access your camera"-Option in the Widows Settings is switched to ON, so all apps are allowed to access the camera.
Xaml
<Page
x:Class="QrCodeTest.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:QrCodeTest"
xmlns:vm="using:QrCodeTest.ViewModels"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Page.DataContext>
<vm:TestViewModel x:Name="ViewModel" />
</Page.DataContext>
<ScrollViewer>
<StackPanel>
<Button Content="Start Preview" HorizontalAlignment="Center" Click="Button_Click" Margin="5" />
<CaptureElement x:Name="capturePreview" HorizontalAlignment="Center" Stretch="Uniform" Width="0" Height="0" Margin="10" />
<Button Content="Stop Preview" HorizontalAlignment="Center" Click="Button_Click_1" Margin="5" />
<TextBlock Text="{Binding Etikett, Mode=TwoWay}" HorizontalAlignment="Center" Margin="5" />
</StackPanel>
</ScrollViewer>
</Page>
CodeBehind
private BarcodeScanner scanner { get; set; }
private ClaimedBarcodeScanner claimedScanner { get; set; }
private MediaCapture captureManager { get; set; }
internal async Task StartScannerAsync () {
capturePreview.Visibility = Visibility.Visible;
capturePreview.Width = 400; capturePreview.Height = 300;
scanner = null;
scanner = await DeviceHelpers.GetFirstDeviceAsync(BarcodeScanner.GetDeviceSelector(connectionTypes), async (id) => await BarcodeScanner.FromIdAsync(id));
if (scanner != null) {
captureManager = new MediaCapture();
claimedScanner = await scanner.ClaimScannerAsync();
if (claimedScanner != null) {
claimedScanner.ReleaseDeviceRequested += claimedScanner_ReleaseDeviceRequested;
claimedScanner.DataReceived += claimedScanner_DataReceived;
claimedScanner.IsDecodeDataEnabled = true;
IReadOnlyList<uint> supportedSymbologies = await scanner.GetSupportedSymbologiesAsync();
foreach (uint symbology in supportedSymbologies) {
listOfSymbologies.Add(new SymbologyListEntry(symbology));
}
await claimedScanner.EnableAsync();
MediaCaptureInitializationSettings _captureInitSettings = new MediaCaptureInitializationSettings {
VideoDeviceId = scanner.VideoDeviceId,
StreamingCaptureMode = StreamingCaptureMode.AudioAndVideo,
PhotoCaptureSource = PhotoCaptureSource.VideoPreview
};
await captureManager.InitializeAsync(_captureInitSettings);
capturePreview.Source = captureManager;
try {
// Change to false, in case you wanna compare different methods of doing the same
bool Like_MP_PAT_UWP = false;
if (Like_MP_PAT_UWP) {
await capturePreview.Source.StartPreviewAsync();
await claimedScanner.StartSoftwareTriggerAsync();
} else {
LocalDataContext.Etikett = "await captureManager.StartPreviewAsync();";
await captureManager.StartPreviewAsync();
await claimedScanner.StartSoftwareTriggerAsync();
Thread.Sleep(2000);
await claimedScanner.StopSoftwareTriggerAsync();
await captureManager.StopPreviewAsync();
LocalDataContext.Etikett = "await capturePreview.Source.StartPreviewAsync();";
await capturePreview.Source.StartPreviewAsync();
await claimedScanner.StartSoftwareTriggerAsync();
Thread.Sleep(2000);
await claimedScanner.StopSoftwareTriggerAsync();
await capturePreview.Source.StopPreviewAsync();
LocalDataContext.Etikett = "await claimedScanner.ShowVideoPreviewAsync();";
await claimedScanner.ShowVideoPreviewAsync();
await claimedScanner.StartSoftwareTriggerAsync();
Thread.Sleep(2000);
await claimedScanner.StopSoftwareTriggerAsync();
claimedScanner.HideVideoPreview();
}
} catch (Exception e) {
Exception x = e; displayRequest.RequestRelease();
} finally {
LocalDataContext.Etikett = string.Empty;
}
}
}
}
ViewModel:
public class TestViewModel: INotifyPropertyChanged {
public static TestViewModel Instance { get; set; }
private string _Etikett;
public string Etikett { get { return _Etikett; } set { _Etikett = value; NotifyPropertyChanged(); } }
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged ([CallerMemberName] String propertyName = "") {
//PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
if (PropertyChanged != null) {
PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
I've wasted already 4 working days just to compare the solutions, the codes etc. The above code was copied from the test-app but it's mostly identical to the one on the main-apps LoginPage (except for the "if (Like_MP_PAT_UWP) {...}".
Every hint is welcome.
Thank you in advance.
The Problem was Kaspersky Endpoint Security's "advanced Threat Protection/host intrusion prevention"-setting. It prevented ALL apps outside from our dev-harddrive (i. e. on our tablets or from our network-drive) to access the camera (Dev-Drive = "Trusted Zone").
It was necessary to reconfigure that feature in Kaspersky Endpoint Security for the whole environment (declare necessary locations/clients as a trusted zone).
Hope, this might help someone with a similar problem or at least give a hint to someone.