Xamarin.Forms example of how to use SkiaSharp to pan and scroll a large image with a fixed size View
Switch branches/tags
Nothing to show
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.



This repository holds an example of the best way I've been able to come up with to handle panning a drawing/graphic rendered with SkiaSharp. It takes from the Xamarin example of applying custom TouchEffects for Finger Painting and applies it to a 2D surface for panning.

Using this method allows you to scroll through larger charts/graphics or even handle pannig on a "zoomed in" image.


How it works


In the Xamarin.Forms project we implement the custom TouchEffects example as described over at the Xamarin documentation (link)

<views:SKCanvasView x:Name="canvasChart" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" EnableTouchEvents="true" PaintSurface="Handle_PaintSurface">
        <e:TouchEffect TouchAction="Handle_TouchAction" Capture="true" />

Deltas are calculated by comparing the touch points between "Moved" touch events. This allows us to continue aggregation of the total X/Y delta during the move. We then apply this delta to all elements painted to the surface thus giving us the "panning" effect

void Handle_TouchAction(object sender, TouchActionEventArgs args)
        //First touch, just mark the location
        if (args.Type == TouchActionType.Pressed)
            _previousTouchPoint = args.Location;
        //User is dragging/moving the chart
        if (args.Type == TouchActionType.Moved)
            //Calculate Deltas in the drag
            var _touchYDelta = (float)Math.Round((_previousTouchPoint.Y - args.Location.Y) * 2, 0);
            var _touchXDelta = (float)Math.Round((_previousTouchPoint.X - args.Location.X) * 2, 0);
            //Re-Draw the Chart
            if (_touchYDelta >= 1 || _touchYDelta <= -1 || _touchXDelta >= 1 || _touchXDelta <= 1)
                _YDelta -= _touchYDelta;
                _XDelta -= _touchXDelta;
                _previousTouchPoint = args.Location;


For the Xamarin.iOS bit, we simply implement the custom TouchEffect as outlined in the Xamarin documentation.


  • You need to have the EnableTouchEvents set to TRUE on the SkiaSharp Canvas in order for the Touch Effects to be invoked.

  • Other Xamarin.Forms controls that make use of "Moved' Touch Effects can interfere with this and cause the drag to be interrupted. An example being the slide out action for a MasterDetail menu. To fix this, you would need to set IsGestureEnabled to FALSE on the MasterDetail page.

  • A good general rule of thumb when working with Touch Actions and Gestures is to keep track on a page which gestures are used where in order to make sure multiple controls are not going to be conflicting with one another.


Example of Panning