Question

我发现了一些关于UICollectionView和iwrong图像问题的帖子，但所有这些都有一个共同点 - 人们试图在cellForItemAt方法中下载图像。我已经在我的应用程序包中有适当的图像，只需使用UIImage（命名:)方法将其设置为UICollectionViewCell。但是我仍然得到错误的图像。有谁可以帮助我？

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return liveChannels.count()
}

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


        let current = liveChannels.channels[indexPath.row]
        let currentProgram = current.currentProgram()

        let channelKey = current.channel?.channelKey
        let programDetail = currentProgram?.name

        if let currentProgress = currentProgram?.progress() {
            cell.progressView.setProgress(currentProgress, animated: true)
        }

        print("\(channelKey) - \(current.channel!.logoName)")
        cell.imageName = current.channel!.logoName
        cell.channelTitleLabel.text = channelKey
        cell.channelDetailLabel.text = programDetail

        cell.channelButton.addTarget(self, action: #selector(ChannelsViewController.pressed(_:)), for: .primaryActionTriggered)
        return cell
    }

我将channelKey和logoName打印到控制台，以确保将正确的图像存储在liveChannels.channels结构中。（确实如此）。

这是我的手机：

class ChannelButtonViewCell: UICollectionViewCell {

    @IBOutlet weak var progressView: UIProgressView!
    @IBOutlet weak var channelButton: ChannelButton!
    @IBOutlet weak var channelDetailLabel: UILabel!
    @IBOutlet weak var channelTitleLabel: UILabel!
    @IBOutlet weak var channelImageView: UIImageView!
    var imageName: String?

    override func prepareForReuse() {

        channelImageView.image = nil

        super.prepareForReuse()
    }

    override func draw(_ rect: CGRect) {
        if (self.isSelected) {
            if let imageName  = imageName {
                channelImageView.image = UIImage(named: imageName)
            }

        } else {
            if let imageName  = imageName {
                channelImageView.image = UIImage(named: imageName.appending("_grey"))
            }

        }
    }
}

Answer 1

1）你应该在非常罕见的情况下覆盖func draw(_ rect: CGRect)而你的情况肯定不是那个。

2）为了确保在分配单元格var imageName: String?时加载和更改图像正好，您可以使用Swift的didSet

3）为确保在选择状态更改时更新图像，您也可以使用didSet。

你最终可能会删除func draw并添加didSet个观察者：

class ChannelButtonViewCell: UICollectionViewCell {

    @IBOutlet weak var progressView: UIProgressView!
    @IBOutlet weak var channelButton: ChannelButton!
    @IBOutlet weak var channelDetailLabel: UILabel!
    @IBOutlet weak var channelTitleLabel: UILabel!
    @IBOutlet weak var channelImageView: UIImageView!
    var imageName: String? {
        didSet {
            updateImage()
        }
    }

    override var isSelected: Bool {
        didSet {
            updateImage()
        }
    }

    override func prepareForReuse() {
        channelImageView.image = nil
        super.prepareForReuse()
    }

    func updateImage() {
        guard let imageName = self.imageName else { return }
        if (self.isSelected) {
            channelImageView.image = UIImage(named: imageName)
        } else {
            channelImageView.image = UIImage(named: imageName.appending("_grey"))
        }
    }

}

如果此解决方案无法解决您的问题，请尝试在func draw()内设置断点并检查它何时被调用以及var imageName中存储的值

UICollectionView显示错误的图像

1 个答案: