magnifying glass displaying irrelevant content in UITextField

问题

I have developed an iOS app in Xamarin. I have few UITExtFields in UIScrollview. when user touch on UITetField, I am setting contentOffSet of scrollview so it can be visible when keyboard appears.

this.txtUsername.ShouldBeginEditing += delegate {
            scrl.SetContentOffset (new CoreGraphics.CGPoint (0, this.txtUsername.ShouldBeginEditing.Frame.Location.Y - 50),true);
            return true;
        };

This works fine. But when I long press on textField, Magnifying glass is appearing and displaying irrelevant detail. -Its displaying detail which is behind the scroll view.

Major problem is- even If I push new viewcontroller, which is SignupView controller, Its displaying Previous screens image in Magnifying glass. Its not problem with only this app, I have similar problem in other app too - which is also developed using Xamarin

I have uploaded video of my app for better understanding of problem I am facing here.

来源：https://stackoverflow.com/questions/40930220/magnifying-glass-displaying-irrelevant-content-in-uitextfield