AdditionalTouchData.md

GestureEventArgs Spec

Additional telemetery data that will be added to Updated events.

Note: Nothing in this specification is guaranteed to be final; all features, implementations, and interfaces are subject to change.

Touch

public class Touch
{
	public int TouchId { get; set; }
	public Point ViewPosition { get; set; }
	public Point PagePosition { get; set; }
	public Point ScreenPosition { get; set; }
	public GestureStatusType StatusType { get; set; }
	View Target { get; }
}

Properties

API	Description
TouchId	A unique identifier for a specific finger in contact with the screen.
ViewPosition	The relative Position of this touch for the given view the gesture is attached to.
PagePosition	The relative Position of this touch to the parent page
ScreenPosition	The absolute Position of the touch on the screen.
GestureStatusType	The state of the touch. This is mainly used when inspecting ChangedTouches to see how said touches have changed
Target	The view associated with this Gesture.

TouchEvent

public class TouchEvent
{
	public IReadOnlyList<Touch> Touches { get; set; }
	public IReadOnlyList<Touch> ChangedTouches { get; set; }
	public IReadOnlyList<Touch> TargetTouches { get; set; }
	View Target { get; }
}

Properties

API	Description
Touches	All active touches and their positions. This will include touches that are happening outside this view
ChangedTouches	All touches that changed from the last event.
TargetTouches	All touches affecting this view

GestureEventArgs

Eventually all of the gestures eventargs will inherit from GestureEventArgs. Initially it'll just be LongPressGestureRecognizer

public class GestureEventArgs : EventArgs
{
	public TouchEvent TouchEvent { get; private set; }
}

Properties

API	Description
TouchEvent	Information about the touch event that caused an update on a gesture.

Examples

public class LongPressContainer : ContentView
{
  BoxView touchView;
  
  public LongPressContainer ()
  {
    var longPressGesture = new LongPressGestureRecognizer ();
    longPressGesture.LongPressUpdated += OnLongPressUpdated;
    GestureRecognizers.Add (longPressGesture);
    
    touchView = new BoxView {WidthRequest = 20, HeightRequest = 20, Color = Color.Red};
  }

  void OnLongPressUpdated (object sender, LongPressUpdatedEventArgs e)
  {
    TouchEvent data = e.TouchEvent;
    if(e.StatusType == GestureStatus.Started || e.StatusType == GestureStatus.Running)
    {
    	var touch = data.TargetTouches[0].ViewPosition;
	AbsoluteLayout.SetLayoutBounds (touchView, new Rectangle (touch.X, touch.Y, 20, 20));
	touchView.Color = Color.Red;
	touchView.IsVisible = true;
    }
    else 
    {
    	touchView.IsVisible = false;
    }
  }
}

This example demonstrates a user long pressing a ContentView which will cause a red BoxView to appear under the finger. Now as the user moves their finger around on the screen the box will follow the finger. Once they lift their finger the BoxView will vanish.