当用户向下滚动时，材质浮动操作按钮应该不可见，向上滚动时应该可见 [英] Material floating action button should invisible when user scroll down and visible when scrolls up

问题描述

我在屏幕右下角有材质浮动操作按钮 (FAB).另外，我在 View 中有 CollectionView.我希望完成以下操作.

I have material Floating action button (FAB) at right bottom of screen. Also, I have CollectionView inside View. I want below actions to be done.

1. 当用户向下滚动时 - FAB 应该不可见.
2. 当用户向上滚动时 - FAB 应该可见.

我在谷歌上到处搜索.没有一个问题满足我的要求.

I've searched everywhere in google.None of questions satisfied my requirements.

推荐答案

不要忘记设置 collectionView.delegate = self.

don't forget to set collectionView.delegate = self.

extension ViewController: UIScrollViewDelegate{
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if scrollView == collectoinView{
            button.isHidden = scrollView.contentOffset.y > 50
        }
    }
}

50 是按钮将隐藏的 Y 位置.您可以根据您的要求调整到任何数字.

50 is the position of Y from which the button will hide. You can adjust to any number according to your requirement.

另一种方法

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {

    let targetPoint = targetContentOffset as? CGPoint
    let currentPoint = scrollView.contentOffset

    if (targetPoint?.y ?? 0.0) > currentPoint.y {
        print("up")

    } else {
        print("down")
     }
}

使用第二种方法，不需要提供静态值.第二种方法已经从objective-c转换为Swift Answer

with the second approach, there is no need to provide static value. the second approach has been converted to Swift from objective-c Answer

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