uitableview - 在 UITableViewCell 自定义类的 UIView 属性上添加 UISwipeGestureRecognizer

Question

我有一个自定义的 UITableViewCell 类，它的初始化方法如下所示:

init(style: UITableViewCellStyle, reuseIdentifier: String!) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)

        let swipeLeft: UISwipeGestureRecognizer = UISwipeGestureRecognizer(target: self, action: "swipedLeft")
        let swipeRight: UISwipeGestureRecognizer = UISwipeGestureRecognizer(target: self, action: "swipedRight")

        swipeLeft.direction = UISwipeGestureRecognizerDirection.Left
        swipeRight.direction = UISwipeGestureRecognizerDirection.Right

        self.topLayerView?.addGestureRecognizer(swipeLeft)
        self.topLayerView?.addGestureRecognizer(swipeRight)
    }

self.topLayerView 是一个 IBOutlet。问题是当我添加 gestureRecognizers 时，self.topLayerView 是 nil。

如果我在 init 方法中写这样的东西:

if self.topLayerView? {
            println("NOT empty")
        } else {
            println("empty")
        }

它总是给我“空”。所以，我的问题是:将这段代码放在哪里比较合适？

如有任何帮助，我们将不胜感激!

Answer 1

Init 在您的 View 的生命周期中太早，无法期望任何 IBOutlets 已设置。我建议将您的代码移动到单元格的 awakeFromNib() 方法，该方法在接口(interface)文件完全加载后被调用。您可以在 NSObject UIKit Additions Reference 中找到有关此方法和其他方法的更多信息.

override func awakeFromNib() {
    super.awakeFromNib()

    let swipeLeft: UISwipeGestureRecognizer = UISwipeGestureRecognizer(target: self, action: "swipedLeft")
    let swipeRight: UISwipeGestureRecognizer = UISwipeGestureRecognizer(target: self, action: "swipedRight")

    swipeLeft.direction = UISwipeGestureRecognizerDirection.Left
    swipeRight.direction = UISwipeGestureRecognizerDirection.Right

    self.topLayerView?.addGestureRecognizer(swipeLeft)
    self.topLayerView?.addGestureRecognizer(swipeRight)
}