在情节提要中,单元格中的子视图(称为“缩略图”)具有一组约束条件
然后在我的自定义collectionView单元中:
PostViewCell类:UICollectionViewCell {
var portrait: Bool? {
didSet {
if portrait == true {
print(self.bounds.height)
thumbnailWidthConstraint.constant = self.bounds.width
thumbnailHeightConstraint.constant = self.bounds.height/2
thumbnailHeightConstraint.isActive = true
} else {
thumbnailWidthConstraint.constant = self.bounds.width/2
thumbnailHeightConstraint.constant = self.bounds.height
}
self.layoutIfNeeded()
}
}
@IBOutlet weak var thumbnailCenterYConstraint: NSLayoutConstraint!
@IBOutlet weak var thumbnailWidthConstraint: NSLayoutConstraint!
@IBOutlet weak var thumbnailHeightConstraint: NSLayoutConstraint!
@IBOutlet weak var thumbnailCenterXConstraint: NSLayoutConstraint!
override func layoutSubviews() {
if self.bounds.width > self.bounds.height {
portrait = false
} else {
portrait = true
}
super.layoutSubviews()
}
}
我的目标是更改缩略图的高度和宽度,就像在portrait变量的didSet方法中看到的那样。但是,到目前为止,这似乎没有成功。它输出的self.bounds.height为536,在应用程序中似乎是这个高度,而不是我尝试在约束中设置的高度的一半。我想走哪一步?为什么这不起作用?谢谢!
编辑:在包含collectionView单元格的视图控制器中:
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
postsCollectionView.collectionViewLayout.invalidateLayout()
postsCollectionView.layoutIfNeeded()
super.viewWillTransition(to: size, with: coordinator)
}
此集合视图在我的视图控制器中称为“ postsCollectionView”。另外,我有这个:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
if collectionView == timelineCollectionView {
return CGSize(width: CGFloat(2.5), height: collectionView.bounds.height)
} else {
return CGSize(width: collectionView.bounds.size.width, height: collectionView.bounds.size.height)
}
}
因此,当我旋转手机时,collectionView变得比高度还宽,内部的单元也是如此。希望这会设置单元格以重新布局子视图并按照我的定义更改约束。
答案 0 :(得分:1)
更改常数后,您可能会错过重新布局
var portrait: Bool? {
didSet {
if portrait == true {
print(self.bounds.height)
thumbnailWidthConstraint.constant = self.bounds.width
thumbnailHeightConstraint.constant = self.bounds.height/2
thumbnailHeightConstraint.isActive = true
} else {
thumbnailWidthConstraint.constant = self.bounds.width/2
thumbnailHeightConstraint.constant = self.bounds.height
}
self.layoutIfNeeded() // or self.contentView.layoutIfNeeded()
}
}
您还需要响应系统方向更改
func viewWillTransition(to size: CGSize,
with coordinator: UIViewControllerTransitionCoordinator) {
collectionView.collectionViewLayout.invalidateLayout()
collectionView.layoutIfNeeded()
}