ios - Collection View 为空时如何显示消息

Question

我试图仅在我的 Collection View 为空时显示一条消息。好吧，当我的 if 为真时，我尝试设置返回 1，但是当我有这个时，它只在我的 Collection View 中显示一个项目(即使我有更多)。当我返回这个(下面的代码)时，它显示了我收藏 View 中的所有项目，但是当我尝试删除它时，最后一个不是“可删除的”，我的意思是，最后一个留在那里。如何仅在我的收藏 View 中没有项目时显示此消息？

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    if self.movies.count > 0 {

        self.favCollectionView.backgroundView = nil

        return self.movies.count
    }
    else {
        let rect = CGRect(x: 0,
                          y: 0,
                          width: self.favCollectionView.bounds.size.width,
                          height: self.favCollectionView.bounds.size.height)
        let noDataLabel: UILabel = UILabel(frame: rect)
        noDataLabel.text = "No favorite movies yet."
        noDataLabel.textAlignment = .center
        noDataLabel.textColor = UIColor.gray
        noDataLabel.sizeToFit()

        self.favCollectionView.backgroundView = noDataLabel

        return 0
    }
}

---

更新

我是这样做的:

func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 2
}


func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    if section == 0 { return self.movies.count}
    else if section == 1 {
        if self.movies.count < 1 { return 1 }
        else { return 0  }
    }
    return 0
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = favCollectionView.dequeueReusableCell(withReuseIdentifier: "FavCollectionCell", for: indexPath) as! FavoritesCollectionViewCell

    if indexPath.section == 0 {

        let movie = movies[indexPath.row]

        let imgStg: String = movie.posterURL!
        let imgURL: URL? = URL(string: imgStg)
        let imgSrc = ImageResource(downloadURL: imgURL!, cacheKey: imgStg)

        cell.favTitleLabel.text = movie.title

        cell.favPosterImageView.layer.cornerRadius = cell.favPosterImageView.frame.size.width/2
        cell.favPosterImageView.clipsToBounds = true

        //image cache with KingFisher
        cell.favPosterImageView.kf.setImage(with: imgSrc)

        return cell

    }

    else {

        let rect = CGRect(x: 0, y: 0, width: self.favCollectionView.frame.width, height: self.favCollectionView.frame.height)
        let noDataLabel: UILabel = UILabel(frame: rect)
        noDataLabel.text = "No favorite movies yet."
        noDataLabel.textAlignment = .center
        noDataLabel.textColor = UIColor.gray
        noDataLabel.sizeToFit()

        let cell = UICollectionViewCell()
        cell.contentView.addSubview(noDataLabel)

        return cell

    }

}

对于@Lamar 的解决方案，但应用程序因错误而崩溃:

Answer 1

我在这样的扩展中使用 backgroundView:

extension UICollectionView {

    func setEmptyMessage(_ message: String) {
        let messageLabel = UILabel(frame: CGRect(x: 0, y: 0, width: self.bounds.size.width, height: self.bounds.size.height))
        messageLabel.text = message
        messageLabel.textColor = .black
        messageLabel.numberOfLines = 0;
        messageLabel.textAlignment = .center;
        messageLabel.font = UIFont(name: "TrebuchetMS", size: 15)
        messageLabel.sizeToFit()

        self.backgroundView = messageLabel;
    }

    func restore() {
        self.backgroundView = nil
    }
}

我这样使用它:

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    if (self.movies.count == 0) {
        self.collectionView.setEmptyMessage("Nothing to show :(")
    } else {
        self.collectionView.restore()
    }

    return self.movies.count
}