在 Hololens 1 的 2D UWP 应用程序中检测 air-tap 事件

Question

I am trying to detect an air-tap event in my 2D UWP application for Hololens 1. I am using VS 2019 for my development. I have followed some sample code from BasicHologram and Hands and motion controllers in DirectX . Here is my sample code I wrote:

SpatialInputHandler.cs

public class SpatialInputHandler
{
    private SpatialInteractionManager interactionManager;
    private SpatialInteractionSourceState sourceState;
    public SpatialInputHandler()
    {
        interactionManager = SpatialInteractionManager.GetForCurrentView();
        interactionManager.SourcePressed += this.OnSourcePressed;
    }
    public SpatialInteractionSourceState CheckForInput()
    {
        SpatialInteractionSourceState sourceState = this.sourceState;
        this.sourceState = null;
        return sourceState;
    }
    public void OnSourcePressed(SpatialInteractionManager sender, SpatialInteractionSourceEventArgs args)
    {
        sourceState = args.State;
    }
}

MainPage.cs

public sealed partial class MainPage : Page
{
    private SpatialInputHandler spatialInputHandler;
    DispatcherTimer dispatcherTimer;
    public MainPage()
    {
        this.InitializeComponent();
        spatialInputHandler = new SpatialInputHandler();
        dispatcherTimer = new DispatcherTimer();
        dispatcherTimer.Interval = TimeSpan.FromMilliseconds(60);
        dispatcherTimer.Tick += DispatcherTimer_Tick;
        dispatcherTimer.Start();
    }
    private void DispatcherTimer_Tick(object sender, object e)
    {
        SpatialInteractionSourceState pointerState = spatialInputHandler.CheckForInput();
        if (pointerState != null && pointerState.IsPressed)
        {
            textBlock2.Text = "airtap detected";
        }
        if(pointerState == null)
        {
            textBlock2.Text = "no airtap detected";
        }
    }
}

In my code I am always getting pointerState value as null. Could someone please help me how to figure this out. Thanks!

Answer 1

Because you are develeping a 2d flat app on HoloLens, the SpatialInteractionManager class is not designed for such scenario, it's for holographic apps.

For a flat app, it will run in the shell and as such we would need to handle routed events which are for input and user interaction scenarios(eg touch, mouse, etc…). For example, your UI might have a button( Button inherited from the UIElement base class) and handle the Click or Tap event:

XAML:

<Grid>
        <Button Name="btnClick" Content="Click" Width="100" Height="50" Click="BtnClick_Click" Tapped="BtnClick_Tapped" />
    </Grid>

Backend:

private void BtnClick_Click(object sender, RoutedEventArgs e)
{
    Debug.WriteLine("Clicked");
}

private void BtnClick_Tapped(object sender, TappedRoutedEventArgs e)
{
    Debug.WriteLine("Tapped");
}

These events can respond correctly with your air-tap interaction on HoloLens.

For more details, check our this documentation: Events and routed events overview

If you can share more details about how you want the air tap to interact with your app, we're happy to help you to move forward.