手指向下检测拖曳

Question

I've got a Scroll View with Paging View controller. The interface looks like this:

@interface ScrollViewWithPagingViewController : UIViewController <UIScrollViewDelegate> {
    UIScrollView *scrollView;
    UIPageControl *pageControl;
    NSMutableArray *viewControllers;
}

and it lets me switch pages as expected when you do a swipe.

However, I'd like it to switch pages if you have one finger down and then do a swipe with a second finger which it currently doesn't do. Not quite sure how to proceed though.

• Add a UIGestureRecogniser?

• Subclass UIScrollView?

Answer 1

I would probably set a UIGestureRecognizer on the UIScrollView , specifically a UISwipeGestureRecognizer . Then you would want to set the numberOfTouchesRequired property:

swipeGesture.numberOfTouchesRequired = 2;

With any luck, this gesture will fire and allow you to cancel any other events (so that you don't scroll, or zoom, or...something else).

Answer 2

Just as a hint, if I got you correctly what you are trying to do is a pinch right? Like when you zoom out on iphone. If you keep a finger down and swipe the others in some direction is IMHO a pinch. If that is the gesture you are trying to use you should look into UIGestureRecogniser and in particular into UIPinchGestureRecognizer (check http://bit.ly/f5sZMw ) (developer.apple.com link).

-- Umberto