swift - UICollectionView 什么时候完成加载？

Question

How do I know that the UICollectionView has been loaded completely?我试图在 Swift 中重现这个解决方案，但我在阅读 Obj-C 时遇到了问题。有人可以帮忙吗？

Answer 1

SWIFT 3:@libec 的回答版本

override func viewDidLoad() {
    super.viewDidLoad()
    collectionView.addObserver(self, forKeyPath: "contentSize", options: NSKeyValueObservingOptions.old, context: nil)
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    collectionView.removeObserver(self, forKeyPath: "contentSize")
}

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if let observedObject = object as? UICollectionView, observedObject == collectionView {
        print("done loading collectionView")
    }
}