点击时更改 UICollectionViewCell 内的视图不起作用

Question

我在 UICollectionViewCell 中有一个用户头像列表。当用户点击一个时，我想将所选项目添加到集合中并突出显示它以指示它已被点击。

很遗憾，UI 似乎没有更新。有什么想法吗？

最初我加载图像并将它们设置为圆形。如果需要，我什至可以设置边框颜色，但现在我将其设置为清除。这一切都在加载单元格时起作用：

 func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath as IndexPath) as! UICollectionViewCell
        // Configure the cell
        let member: UserProfile = groupMembers[indexPath.item]
        let imgAvatar = cell.viewWithTag(2) as! UIImageView

        imgAvatar.layer.cornerRadius = contactAvatar.frame.size.width / 2
        imgAvatar.clipsToBounds = true
        imgAvatar.contentMode = UIViewContentMode.scaleAspectFill
        imgAvatar.layer.borderWidth = 2.0
        imgAvatar.layer.borderColor  = UIColor.clear.cgColor
        imgAvatar.layer.cornerRadius = 30.0

        let downloadURL = NSURL(string: member.avatarUrl)!
        imgAvatar.af_setImage(withURL: downloadURL as URL)

        return cell 
    }

现在这里是当您点击集合中任何给定的 UIImageView 时执行的代码，但它似乎没有更新图像：

 ///Fired when tapped on an image of a person
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

         let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath as IndexPath) as! UICollectionViewCell
        let tappedUser: UserProfile = groupMembers[indexPath.item]
        let imgAvatar = cell.viewWithTag(2) as! UIImageView

           ..add item to collection, etc.. 

           //Update imageview to indicate it's been tapped.
           DispatchQueue.main.async {
            contactAvatar.layer.cornerRadius = contactAvatar.frame.size.width / 2
            imgAvatar.clipsToBounds = true
            imgAvatar.contentMode = UIViewContentMode.scaleAspectFill
            imgAvatar.layer.borderWidth = 2.0
            imgAvatar.layer.cornerRadius = 30.0
            imgAvatar.layer.borderColor = UIcolor.blue.cgColor
            }

        }
    }

运行这段代码，它遇到断点表明我已经点击了该项目，但它不会更新 UI。我确信存在一个线程/ui 问题，其中集合视图不是 "redrawing" 我对图像所做的更改。也许我无法更改集合内部视图的外观？

提前感谢您的任何见解。

Answer 1

你的didSelect不正确。从集合视图中获取单元格。 cellForItem

 ///Fired when tapped on an image of a person
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

     let cell = collectionView.cellForItem(at:indexPath) as! UICollectionViewCell
    let tappedUser: UserProfile = groupMembers[indexPath.item]
    let imgAvatar = cell.viewWithTag(2) as! UIImageView

       ..add item to collection, etc.. 

       //Update imageview to indicate it's been tapped.
       DispatchQueue.main.async {
        contactAvatar.layer.cornerRadius = contactAvatar.frame.size.width / 2
        contactAvatar.clipsToBounds = true
        contactAvatar.contentMode = UIViewContentMode.scaleAspectFill
        contactAvatar.layer.borderWidth = 2.0
        contactAvatar.layer.cornerRadius = 30.0
        contactAvatar.layer.borderColor = UIcolor.blue.cgColor
        }

    }
}

使用手机，如果它不起作用请告诉我。

Answer 2

您为获取单元格实例而编写的代码不正确，请使用下面的代码行，其余的似乎都是正确的，希望通过更改此行能够起作用。

    let cell = collectionView.cellForItem(at:indexPath) as! UICollectionViewCell

点击时更改 UICollectionViewCell 内的视图不起作用

Change a view inside of UICollectionViewCell when tapped not working

grand-central-dispatch

ios

uicollectionview

uicollectionviewcell

swift