swift 中的滚动视图 5

Question

如何在 swift 中检测集合视图是否已水平滚动到屏幕的 50%。

我正在尝试使用方法-

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let numberOfImages = imageURLStrings.count
    
    if numberOfImages > 0 {
        let width = scrollView.frame.size.width / 2
            let contentXoffset = scrollView.contentOffset.x
            let distanceToCenter = scrollView.contentSize.width - contentXoffset
        if distanceToCenter < width {
                print(" you reached middle of the screen")
            }
    }
}

当我将集合滚动到屏幕 50% 时，我需要触发服务器调用

任何帮助深表感谢。

Answer 1

 func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let width = scrollView.contentSize.width
    let contentOffSetX = scrollView.contentOffset.x
    let scrolled = width - contentOffSetX
    let half = Int(width / 2 + (collectionView.bounds.width / 2))
    DispatchQueue.main.async {
        if Int(scrolled) == half { // the point when collection view is 50% left and 50%
            self.view.backgroundColor = .red
        } else {
            self.view.backgroundColor = .white
        }
    }

}

如果你想要左 50% 和右 50% 滚动

func scrollViewDidScroll(_ scrollView: UIScrollView) {
        let width = scrollView.contentSize.width
        let contentOffSetX = scrollView.contentOffset.x
        let scrolled = width - contentOffSetX
        let half = Int(width / 2 + (collectionView.bounds.width / 2))
        DispatchQueue.main.async {
            if Int(scrolled) <= half { // the point when collection view is 50% left and 50%
                self.view.backgroundColor = .red
            } else {
                self.view.backgroundColor = .white
            }
        }

    }