Ios 集合视图高度

当键盘弹出时，我使用高度约束来降低集合视图的高度

@objc func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
    self.collectionViewHeightConstraint.constant = 250 - keyboardSize.height/2
        self.addButtonConstraint.constant = keyboardSize.height+20

    }
}

@objc func keyboardWillHide(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
    self.collectionViewHeightConstraint.constant = 250
    self.addButtonConstraint.constant = 20

      }
}

如何使集合视图显示前半部分而不是后半部分

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尝试在keyboardWillShow方法中调用此选项：

collectionView.scrollToTop(false)

延伸

extension UIScrollView {
    func scrollToTop(_ animated: Bool) {
        var topContentOffset: CGPoint
        if #available(iOS 11.0, *) {
            topContentOffset = CGPoint(x: -safeAreaInsets.left, y: -safeAreaInsets.top)
        } else {
            topContentOffset = CGPoint(x: -contentInset.left, y: -contentInset.top)
        }
        setContentOffset(topContentOffset, animated: animated)
    }
}

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我认为作者的意思是显示集合视图的顶部，而您正在检索最后一部分的索引。但是逻辑基本上是一样的这是我的错。。我想请你下楼。答案已编辑