Can you override the Navigation Controllers 'InteractivePopGestureRecognizer' action?

Question

I'm searching for ways to implement a swipe gesture recognizer which only triggers when you swipe from the outer left side of the screen to the right. We need the gesture to open our custom SideMenu. I tried to use a simple UISwipeGestureRecognizer with the SwipeDirection property set to right, but that gets triggered on every swipe from left to right, no matter what the startpoint of the swipe is.

Ideally, we want the animation of it to look and feel like the InteractivePopGestureRecognizer of a UINavigationController. We are already using a NavigationController, which pushed our MainView over our IntroView. Now, we disable the InteractivePopGestureRecognizer, so you aren't able to go back to the IntroView. That's our problem. If it is possible, we don't want to disable the gesture of the NavigationController, but change the action of it. So the swipe from the far left side of the screen to the right would not pop the current viewcontroller, but open our SideMenu.

Is it possible to override the InteractivePopGestureRecognizer to change the action of it? If this isn't possible, do you have another idea on how to create the exact same gesture recognizer? It has to be possible somehow because many apps only open their SideMenu if your startpoint of the gesture is the left (or right) side of the screen. (e.g. Reddit)

Thanks for any help in advance.

Answer 1

You could use Touch Events and UISwipeGestureRecognizer to do that.

The workaround that is override TouchesBegan method to detect the started point whether fit your needs, and if so add UISwipeGestureRecognizer for View.

SwipeGestureRecognizer rightSwipeGesture;

public override void TouchesBegan (NSSet touches, UIEvent evt)
{
    base.TouchesBegan (touches, evt);
    UITouch touch = touches.AnyObject as UITouch;
    if (touch != null)
    {
        //code here to handle touch
         CoreGraphics.CGPoint swipPoint = touch.LocationInView(View);
         if(swipPoint.X < 0.5)
         {
            rightSwipeGesture = new SwipeGestureRecognizer { Direction = SwipeDirection.Right };
            rightSwipeGesture.Swiped += OnSwiped;
            View.AddGestureRecognizers(rightSwipeGesture);
         }
    }
}

public override void TouchesEnded (NSSet touches, UIEvent evt)
{
    base.TouchesBegan (touches, evt);
    if(null != rightSwipeGesture ){
        rightSwipeGesture.Swiped -= OnSwiped;
        View.RemoveGestureRecognizers(rightSwipeGesture);
    }
}

=============================Update=================================

I found a workaround only use one GestureRecognizer will make it works. You could have a look at UIScreenEdgePanGestureRecognizer. Although it's a Pan gesture, however if you not deal with somethind with the added view, it will work as a swip gesture. In addition, UIScreenEdgePanGestureRecognizer only can work when on the screen edge. You could set the Left edge to handle your needs.

For example:

UIScreenEdgePanGestureRecognizer panRightGestureRecognizer = new UIScreenEdgePanGestureRecognizer();
panRightGestureRecognizer.Edges = UIRectEdge.Left;
panRightGestureRecognizer.AddTarget(() => HandleSwap(panRightGestureRecognizer));
View.AddGestureRecognizer(panRightGestureRecognizer);

private void HandleSwip(UIScreenEdgePanGestureRecognizer panRightGestureRecognizer)
{
     Point point = (Point)panRightGestureRecognizer.TranslationInView(View);
     if (panRightGestureRecognizer.State == UGestureRecognizerState.Began)
     {
         Console.WriteLine("Show slider view");
     }
}