Defining a method for calculating the state 

Let's add the CalculatePanState() method to calculate how far we have panned the image, and if it should start to affect the GUI, by following these few steps:

1. Open Controls/SwiperControl.xaml.cs.
2. Add the properties at the top and the CalculatePanState() method anywhere in the class, as shown in the following code block:

private const double DeadZone = 0.4d;
private const double DecisionThreshold = 0.4d;

private void CalculatePanState(double panX)
{
    var halfScreenWidth = _screenWidth / 2;
    var deadZoneEnd = DeadZone * halfScreenWidth;
 
    if (Math.Abs(panX) < deadZoneEnd)
    {
        return;
    }
 
    var passedDeadzone = panX < 0 ? panX + deadZoneEnd : panX - 
    deadZoneEnd;
    var decisionZoneEnd = DecisionThreshold * halfScreenWidth;
    var opacity = passedDeadzone / decisionZoneEnd;
 
    opacity = Clamp(opacity, -1, 1);
 
    likeStackLayout.Opacity = opacity;
    denyStackLayout.Opacity = -opacity;
} 

We define...