How to enable zoom in and zoom out on a contentpage in xamarin forms?

Question

How can I enable zoom on a contentpage in xamarin forms? Is it possible to enable it on the entire contentpage? Or is it only possible to zoom in on images?

Answer 1

You can use the pinch gesture inside a ContentPage, here is the official page:

https://developer.xamarin.com/guides/xamarin-forms/user-interface/gestures/pinch/

and for the entire project sample:

https://github.com/xamarin/xamarin-forms-samples/tree/master/WorkingWithGestures/PinchGesture

Here is an example of what you can achieve:

Xamarin.Forms Pinch Example

Answer 2

Try this Class , this solution do not scroll when you zoom . Source found here: Source Code

    public class PinchToZoomContainer : ContentView {
    double currentScale = 1;
    double startScale = 1;
    double xOffset = 0;
    double yOffset = 0;

    public PinchToZoomContainer ()
    {
        var pinchGesture = new PinchGestureRecognizer ();
        pinchGesture.PinchUpdated += OnPinchUpdated;
        GestureRecognizers.Add (pinchGesture);
    }

    void OnPinchUpdated (object sender, PinchGestureUpdatedEventArgs e)
    {
        if (e.Status == GestureStatus.Started) {
            // Store the current scale factor applied to the wrapped user interface element,
            // and zero the components for the center point of the translate transform.
            startScale = Content.Scale;
            Content.AnchorX = 0;
            Content.AnchorY = 0;
        }
        if (e.Status == GestureStatus.Running) {
            // Calculate the scale factor to be applied.
            currentScale += (e.Scale - 1) * startScale;
            currentScale = Math.Max (1, currentScale);

            // The ScaleOrigin is in relative coordinates to the wrapped user interface element,
            // so get the X pixel coordinate.
            double renderedX = Content.X + xOffset;
            double deltaX = renderedX / Width;
            double deltaWidth = Width / (Content.Width * startScale);
            double originX = (e.ScaleOrigin.X - deltaX) * deltaWidth;

            // The ScaleOrigin is in relative coordinates to the wrapped user interface element,
            // so get the Y pixel coordinate.
            double renderedY = Content.Y + yOffset;
            double deltaY = renderedY / Height;
            double deltaHeight = Height / (Content.Height * startScale);
            double originY = (e.ScaleOrigin.Y - deltaY) * deltaHeight;

            // Calculate the transformed element pixel coordinates.
            double targetX = xOffset - (originX * Content.Width) * (currentScale - startScale);
            double targetY = yOffset - (originY * Content.Height) * (currentScale - startScale);

            // Apply translation based on the change in origin.
            Content.TranslationX = targetX.Clamp (-Content.Width * (currentScale - 1), 0);
            Content.TranslationY = targetY.Clamp (-Content.Height * (currentScale - 1), 0);

            // Apply scale factor
            Content.Scale = currentScale;
        }
        if (e.Status == GestureStatus.Completed) {
            // Store the translation delta's of the wrapped user interface element.
            xOffset = Content.TranslationX;
            yOffset = Content.TranslationY;
        }
    }
}

Helper DoubleExtensions

    public static class DoubleExtensions
{
    public static double Clamp (this double self, double min, double max)
    {
        return Math.Min (max, Math.Max (self, min));
    }
}