Ios Swift collectionview单元格动画仅在滚动时运行

我正在尝试在列表和网格布局之间设置collectionview的动画

它可以在两个布局之间设置动画，但是我不知道如何设置一些约束的动画

例如：

这只会在我开始滚动并在屏幕上显示新项目时更改约束。我想在更改布局时更改约束

更改布局的方法：

@IBAction func gridButtonDidTouch(_ sender: AnyObject) {        
        if collectionView.collectionViewLayout == gridLayout {
            // list layout
            UIView.animate(withDuration: 0.1, animations: {
                self.collectionView.collectionViewLayout.invalidateLayout()
                self.collectionView.setCollectionViewLayout(self.listLayout, animated: false)
            })
        } else {
            // grid layout
            UIView.animate(withDuration: 0.1, animations: {
                self.collectionView.collectionViewLayout.invalidateLayout()
                self.collectionView.setCollectionViewLayout(self.gridLayout, animated: false)
            })
        }

    }


override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransition(to: size, with: coordinator)
        collectionView.collectionViewLayout.invalidateLayout()
    }

class GridLayout: UICollectionViewFlowLayout {

    var numberOfColumns: Int = 3

    init(numberOfColumns: Int) {
        super.init()
        minimumLineSpacing = 1
        minimumInteritemSpacing = 1

        self.numberOfColumns = numberOfColumns
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override var itemSize: CGSize {
        get {
            if let collectionView = collectionView {
                let itemWidth: CGFloat = (collectionView.frame.width/CGFloat(self.numberOfColumns)) - self.minimumInteritemSpacing
                let itemHeight: CGFloat = 260.0
                return CGSize(width: itemWidth, height: itemHeight)
            }

            // Default fallback
            return CGSize(width: 100, height: 100)
        }
        set {
            super.itemSize = newValue
        }
    }

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint) -> CGPoint {
        return proposedContentOffset
    }

}


class ListLayout: UICollectionViewFlowLayout {

    var itemHeight: CGFloat = 180

    init(itemHeight: CGFloat) {
        super.init()
        minimumLineSpacing = 1
        minimumInteritemSpacing = 1

        self.itemHeight = itemHeight
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override var itemSize: CGSize {
        get {
            if let collectionView = collectionView {
                let itemWidth: CGFloat = collectionView.frame.width
                return CGSize(width: itemWidth, height: self.itemHeight)
            }

            // Default fallback
            return CGSize(width: 100, height: 100)
        }
        set {
            super.itemSize = newValue
        }
    }

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint) -> CGPoint {
        return proposedContentOffset
    }

}

---

你试过在“self.collectionView.setCollectionViewLayout（self.listlaway，animated:false）”中将“animated”改为true吗？@almas是的，我试过了，同样的事情也发生了。你试过在“self.collectionView.setCollectionViewLayout（self.listlawlayout，animated:false）”中将“animated”改为true吗？@almas是的，我试过，同样的事情也会发生

@IBAction func gridButtonDidTouch(_ sender: AnyObject) {        
        if collectionView.collectionViewLayout == gridLayout {
            // list layout
            UIView.animate(withDuration: 0.1, animations: {
                self.collectionView.collectionViewLayout.invalidateLayout()
                self.collectionView.setCollectionViewLayout(self.listLayout, animated: false)
            })
        } else {
            // grid layout
            UIView.animate(withDuration: 0.1, animations: {
                self.collectionView.collectionViewLayout.invalidateLayout()
                self.collectionView.setCollectionViewLayout(self.gridLayout, animated: false)
            })
        }

    }


override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransition(to: size, with: coordinator)
        collectionView.collectionViewLayout.invalidateLayout()
    }

class GridLayout: UICollectionViewFlowLayout {

    var numberOfColumns: Int = 3

    init(numberOfColumns: Int) {
        super.init()
        minimumLineSpacing = 1
        minimumInteritemSpacing = 1

        self.numberOfColumns = numberOfColumns
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override var itemSize: CGSize {
        get {
            if let collectionView = collectionView {
                let itemWidth: CGFloat = (collectionView.frame.width/CGFloat(self.numberOfColumns)) - self.minimumInteritemSpacing
                let itemHeight: CGFloat = 260.0
                return CGSize(width: itemWidth, height: itemHeight)
            }

            // Default fallback
            return CGSize(width: 100, height: 100)
        }
        set {
            super.itemSize = newValue
        }
    }

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint) -> CGPoint {
        return proposedContentOffset
    }

}


class ListLayout: UICollectionViewFlowLayout {

    var itemHeight: CGFloat = 180

    init(itemHeight: CGFloat) {
        super.init()
        minimumLineSpacing = 1
        minimumInteritemSpacing = 1

        self.itemHeight = itemHeight
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override var itemSize: CGSize {
        get {
            if let collectionView = collectionView {
                let itemWidth: CGFloat = collectionView.frame.width
                return CGSize(width: itemWidth, height: self.itemHeight)
            }

            // Default fallback
            return CGSize(width: 100, height: 100)
        }
        set {
            super.itemSize = newValue
        }
    }

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint) -> CGPoint {
        return proposedContentOffset
    }

}