UIScrollView scrollsToTop Property

UIScrollView scrollsToTop Property
A Boolean value that controls whether the scroll-to-top gesture is enabled.

Declaration
SWIFT
var scrollsToTop: Bool
OBJECTIVE-C
@property(nonatomic) BOOL scrollsToTop

Discussion
The scroll-to-top gesture is a tap on the status bar. When a user makes this gesture, the system asks the scroll view closest to the status bar to scroll to the top. If that scroll view has scrollsToTop set to NO, its delegate returns NO from scrollViewShouldScrollToTop:, or the content is already at the top, nothing happens.

After the scroll view scrolls to the top of the content view, it sends the delegate a scrollViewDidScrollToTop:message.

The default value of scrollsToTop is YES. 

Special Considerations
On iPhone, the scroll-to-top gesture has no effect if there is more than one scroll view on-screen that has scrollsToTop set to YES.

Availability
Available in iOS 2.0 and later.

如果屏幕上有一个以上的 scroll view的 scrollsToTop属性为 YES，则滚动到顶部的手势无效。