ios - UICollectionView 每 3 秒自动垂直滚动一次

Question

我有一个应用程序需要在 Collection View 中自动滚动

class resultsViewController: UIViewController , UICollectionViewDataSource , UICollectionViewDelegate {

    @IBOutlet weak var collectionView: UICollectionView!
    var numberCount = 3
    var scrollIndex = 1
    override func viewDidLoad() {
        super.viewDidLoad()

          let flow = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
        flow.sectionInset = UIEdgeInsetsMake(0, 0, 0, 0)
        let width = UIScreen.mainScreen().bounds.size.width - 6
        flow.itemSize = CGSizeMake(width/3, width/3)
        flow.minimumInteritemSpacing = 3
        flow.minimumLineSpacing = 3
        flow.sectionInset = UIEdgeInsetsMake(0.0, 0.0,10,0);





        // Do any additional setup after loading the view.
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        let delayTime = dispatch_time(DISPATCH_TIME_NOW, Int64(3 * Double(NSEC_PER_SEC)))
        dispatch_after(delayTime, dispatch_get_main_queue()) {
            self.doAfterThreeSecods()
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("imageSearch", forIndexPath: indexPath) as! imagesCollectionViewCell
        return cell
    }
    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return numberCount
    }

    func doAfterThreeSecods()
    {

        numberCount += 3
        collectionView.reloadData()

        let delayTime = dispatch_time(DISPATCH_TIME_NOW, Int64(3 * Double(NSEC_PER_SEC)))
        dispatch_after(delayTime, dispatch_get_main_queue()) {

            self.doAfterThreeSecods()
        }
    }

}

每三秒追加 3 个单元格

当我追加三个单元格时，我只需要滚动下一行

  self.collectionView.layoutIfNeeded()
        self.collectionView.scrollToItemAtIndexPath(NSIndexPath(index: self.scrollIndex), atScrollPosition: UICollectionViewScrollPosition.Bottom, animated: true)

但是应用程序崩溃并且错误是:

由于未捕获的异常“NSInvalidArgumentException”而终止应用，原因:“尝试滚动到无效索引路径:{length = 1，path = 6}”

任何人都可以提供帮助

Answer 1

您这样做的方式是错误的。这就是它抛出无效索引路径错误的原因。例如，假设您有 3 个 Collection View 要显示。我们将其命名为 image01、image02、image03。所以你的数组应该像[image03,image01,image02,image03,image01]。您应该将最后一个元素附加到第一个元素，将第一个元素附加到最后一个元素。答案非常广泛，难以描述。因此这里有一篇描述这个理论的文章。

 Article :- 

https://adoptioncurve.net/archives/2013/07/building-a-circular-gallery-with-a-uicollectionview/