以编程方式将 UIScrollView 滚动到 Swift 中的子 UIView(子视图)的顶部

问题描述

我的 UIScrollView 中有一些屏幕内容，它们只能垂直滚动.

I have a few screens worth of content within my UIScrollView which only scrolls vertically.

我想以编程方式滚动到包含在其层次结构中某处的视图.

I want to programmatically scroll to a view contained somewhere in it's hierarchy.

UIScrollView 移动，以便子视图位于 UIScrollView 的顶部(动画与否)

The UIScrollView move so that the child view is at the top of the UIScrollView (either animated or not)

推荐答案

这是我最后写的一个扩展.

Here's an extension I ended up writing.

用法:

从我的 viewController 调用，self.scrollView 是 UIScrollView 的出口，self.commentsHeader 是其中的一个视图，靠近底部:

Called from my viewController, self.scrollView is an outlet to the UIScrollView and self.commentsHeader is a view within it, near the bottom:

self.scrollView.scrollToView(self.commentsHeader, animated: true)

代码:

您只需要 scrollToView 方法，但也保留 scrollToBottom/scrollToTop 方法，因为您可能也需要这些方法，但感觉可以随意删除.

You only need the scrollToView method, but leaving in scrollToBottom / scrollToTop methods too as you'll probably need those too, but feel free to delete them.

extension UIScrollView {

    // Scroll to a specific view so that it's top is at the top our scrollview
    func scrollToView(view:UIView, animated: Bool) {
        if let origin = view.superview {
            // Get the Y position of your child view
            let childStartPoint = origin.convertPoint(view.frame.origin, toView: self)
            // Scroll to a rectangle starting at the Y of your subview, with a height of the scrollview
            self.scrollRectToVisible(CGRect(x:0, y:childStartPoint.y,width: 1,height: self.frame.height), animated: animated)
        }
    }

    // Bonus: Scroll to top
    func scrollToTop(animated: Bool) {
        let topOffset = CGPoint(x: 0, y: -contentInset.top)
        setContentOffset(topOffset, animated: animated)
    }

    // Bonus: Scroll to bottom
    func scrollToBottom() {
        let bottomOffset = CGPoint(x: 0, y: contentSize.height - bounds.size.height + contentInset.bottom)
        if(bottomOffset.y > 0) {
            setContentOffset(bottomOffset, animated: true)
        }
    }

}

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