首先,这是我的视图层次结构:
- Table view
-- Table view cell (loaded from custom xib)
--- Collection view
---- Collection view cell (loaded from custom xib)
----- Custom view (loaded from custom xib)
我遇到的麻烦是,我正在将最后一个视图(自定义视图)作为自定义xib加载到集合视图单元格中。由于某种原因,它的尺寸不正确:
如您所见,视图上方有一个巨大的空白,而不是正确地填充了单元格。有趣的是,如果我稍微向下移动表格视图,然后再向上滚动,它应该显示在它上面:
这是我的收藏夹查看代码的一部分:
// I use this to size the collection view cells to be of 16:9 ratio, nothing crazy
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
// Get the width of the screen
let width = UIScreen.main.bounds.width
let imageWidth = width
let imageHeight = imageWidth / (16 / 9)
self.postMediaHeight = imageHeight
return CGSize(width: imageWidth, height: imageHeight)
}
// Here I initialize the cell
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "PostMediaCollectionViewCell", for: indexPath as IndexPath) as? PostMediaCollectionViewCell else {
fatalError("The dequeued cell is not an instance of PostMediaCollectionViewCell.")
}
let media = post.images[indexPath.row]
cell.initialize()
return cell
}
这是我的集合视图单元格类,PostMediaCollectionViewCell
。没有什么不寻常的:
class PostMediaCollectionViewCell: UICollectionViewCell {
@IBOutlet weak var container: UIView!
@IBOutlet weak var imageView: UIImageView!
@IBOutlet weak var moreView: UIView!
@IBOutlet weak var moreViewLabel: UILabel!
@IBOutlet weak var myCustomView: MyCustomView!
override func awakeFromNib() {
super.awakeFromNib()
}
func initialize() {
//
}
}
最后,这是我的MyCustomView
课程:
class MyCustomView: UIView {
@IBOutlet var rootView: UIView!
@IBOutlet weak var videoView: VideoView!
override init(frame: CGRect) {
super.init(frame: frame)
initialize()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
initialize()
}
func initialize() {
Bundle.main.loadNibNamed("MyCustomView", owner: self, options: nil)
addSubview(rootView)
rootView.frame = self.bounds
rootView.autoresizingMask = [.flexibleHeight, .flexibleWidth]
}
}
我已经确保在我的xib中设置了我的约束,所以自动布局应该可以正常工作,但是显然不是:
PostMediaCollectionViewCell xib:https://i.stack.imgur.com/GQLpj.png
MyCustomView xib:https://i.stack.imgur.com/jpSi0.png
所以我在这里做错了什么?
在行rootView.frame = self.bounds
上添加断点并检查self.bounds
值。如果值与滚动后的值不同,则应更改awakeFromNib
方法。
las PostMediaCollectionViewCell:UICollectionViewCell {
@IBOutlet weak var container: UIView!
@IBOutlet weak var imageView: UIImageView!
@IBOutlet weak var moreView: UIView!
@IBOutlet weak var moreViewLabel: UILabel!
@IBOutlet weak var myCustomView: MyCustomView!
override func awakeFromNib() {
super.awakeFromNib()
self.myCustomView.frame = self.bounds
self.myCustomView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
}
func initialize() {
//
}
}
所以我找到了解决方案,但是我不知道它为什么起作用,以及它是否是解决它的最佳方法,所以我正在寻找输入。
如果我将我的PostMediaCollectionViewCell
类修改为在初始化函数中包含layoutIfNeeded()
,它将起作用:
class PostMediaCollectionViewCell: UICollectionViewCell {
@IBOutlet weak var container: UIView!
@IBOutlet weak var imageView: UIImageView!
@IBOutlet weak var moreView: UIView!
@IBOutlet weak var moreViewLabel: UILabel!
@IBOutlet weak var myCustomView: MyCustomView!
override func awakeFromNib() {
super.awakeFromNib()
}
func initialize() {
layoutIfNeeded()
}
}
但是我不明白为什么。有人可以解释吗?