我有一个程序(WinRT),显示来自网络摄像头的视频流。在初始化 Media Foundation 之前和之后,programm调用函数 ShowMessage 。我评论了这些电话。如果代码运行,如下所示,我可以看到来自网络摄像头的视频流。 但是,如果我取消注释呼叫功能 ShowMessage ,第一次呼叫(//第一次呼叫)完成,来自网络摄像头的视频流将显示,但第二次呼叫( //第二次呼叫)不是呼叫。(我没有看到第二条消息)。我怎么能这样做,来自网络摄像头的视频流将显示,并将同时调用ShowMessage?
XAML:
<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
<CaptureElement x:Name="myCaptureElement" Margin="504,124,400,350" FlowDirection="RightToLeft" HorizontalAlignment="Center" VerticalAlignment="Center" Stretch="Fill" MinWidth="300" MinHeight="200" Height="294" Width="462" />
<Rectangle x:Name="rect1" Fill="#FFF4F4F5" HorizontalAlignment="Left" Height="100" Margin="43,292,0,0" Stroke="Black" VerticalAlignment="Top" Width="100"/>
</Grid>
C#:
public MainPage()
{
this.InitializeComponent();
Func<Task> unnamed = async () =>
{
await TestPhoto();
};
unnamed();
}
private async Task TestPhoto()
{
try
{
//await ShowMessage("Do something",true);//first call
var devInfoCollection = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);
var settings = new Windows.Media.Capture.MediaCaptureInitializationSettings();
settings.VideoDeviceId = devInfoCollection[0].Id;
var mediaCaptureMgr = new MediaCapture();
await mediaCaptureMgr.InitializeAsync();
mediaCaptureMgr.SetPreviewMirroring(true);
myCaptureElement.Source = mediaCaptureMgr;
await mediaCaptureMgr.StartPreviewAsync();
ImageEncodingProperties imageProperties2 = ImageEncodingProperties.CreateJpeg();
var memStream3 = new Windows.Storage.Streams.InMemoryRandomAccessStream();
var mediaCaptureMgr1 = new MediaCapture();
await mediaCaptureMgr1.InitializeAsync();
mediaCaptureMgr1.SetPreviewMirroring(true);
await mediaCaptureMgr1.CapturePhotoToStreamAsync(imageProperties2, memStream3);
await memStream3.FlushAsync();
memStream3.Seek(0);
WriteableBitmap wp1 = new WriteableBitmap(1, 1); ;
await wp1.SetSourceAsync(memStream3);
//await ShowMessage("Do something",false);//second call
}
catch (Exception)
{
}
}
public async Task ShowMessage(String s, bool b)
{
await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
if (b)
{
rect1.Visibility=Visibility.Collapsed;
}
else
{
rect1.Visibility=Visibility.Visible;
}
});
Random r=new Random();
await new MessageDialog(s+" "+r.Next(1000), "Information").ShowAsync();
}