ios - 执行按钮操作后 UICollectionView rollToItemAtIndex

Question

当弹出 currentViewController 时，我想将 mainViewController 中的 UICollectionView 滚动到 currentViewController 当前所在的项目的索引。我已经尝试在 currentViewController 的 viewWillDisappear 中实现它，但是当执行 back button 操作时没有任何反应。

   override func viewWillDisappear(animated : Bool) {
        super.viewWillDisappear(animated)
        if (self.isMovingFromParentViewController()){
            let parent = parentViewController as! UINavigationController
            let child = parent.childViewControllers[0] as! MainViewController
            child.collectionView?.scrollToItemAtIndexPath(NSIndexPath(forItem: currentIndex, inSection: 0), atScrollPosition: .Top, animated: true)
        }
    }

Answer 1

因为您不是关闭而是弹出 View Controller ，这样的操作应该有效:

override func viewWillDisappear(animated: Bool) {
    if let mainViewController = navigationController?.topViewController as? MainViewController {
        mainViewController.collectionView?.scrollToItemAtIndexPath(NSIndexPath(forItem: currentIndex, inSection: 0), atScrollPosition: .CenteredVertically, animated: false)
    }
    super.viewWillDisappear(animated)
}