UICollectionView reloadSection不会从视图层次结构中删除旧视图

Question

UICollectionView在重新加载部分时不会从视图层次结构中删除可重用视图。这会造成UIAutomation的问题。

我创建了一个简单的应用程序，它使用UICollectionView并显示页眉，页脚和单元格。在点击“Reload”时，collectionView显示不同数量的单元格。请参考下面的图片。

在启动应用程序，它显示了2个细胞。点击“Reload”第一次显示8 cells和点击“Reload”第二次显示18 cells。点击“重新加载”第三次显示2个单元格。现在，在这一刻，如果我们使用Xcode View debugger调试视图，那么在禁用“仅显示显示的视图”时，它会在视图层次结构中显示多个单元格。请参考以下图片：

这也是UIAutomation在获得元素创造的问题。我不确定我的实施有什么问题。

下面是我的控制器代码：

struct CellData { 
    var title: String 
    var value: String 
} 

class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout { 

    @IBOutlet var collectionView: UICollectionView! 
    private var data: [CellData]! 
    private var data1: [CellData]! 
    private var data2: [CellData]! 
    private var data3: [CellData]! 
    private var reloadIndex = 1 
    private var activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.Gray) 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     // Do any additional setup after loading the view, typically from a nib. 

     self.data1 = [ 
      CellData(title: "Cell Title 1", value: "Value 1"), 
      CellData(title: "Cell Title 2", value: "Value 2")] 
     self.data = self.data1 

     self.data2 = [ 
      CellData(title: "Cell Title 1", value: "Value 1"), 
      CellData(title: "Cell Title 2", value: "Value 2"), 
      CellData(title: "Cell Title 3", value: "Value 3"), 
      CellData(title: "Cell Title 4", value: "Value 4"), 
      CellData(title: "Cell Title 5", value: "Value 5"), 
      CellData(title: "Cell Title 6", value: "Value 6"), 
      CellData(title: "Cell Title 7", value: "Value 7"), 
      CellData(title: "Cell Title 8", value: "Value 8")] 

     self.data3 = [ 
      CellData(title: "Cell Title 1", value: "Value 1"), 
      CellData(title: "Cell Title 2", value: "Value 2"), 
      CellData(title: "Cell Title 3", value: "Value 3"), 
      CellData(title: "Cell Title 4", value: "Value 4"), 
      CellData(title: "Cell Title 5", value: "Value 5"), 
      CellData(title: "Cell Title 6", value: "Value 6"), 
      CellData(title: "Cell Title 7", value: "Value 7"), 
      CellData(title: "Cell Title 8", value: "Value 8"), 
      CellData(title: "Cell Title 9", value: "Value 9"), 
      CellData(title: "Cell Title 10", value: "Value 10"), 
      CellData(title: "Cell Title 11", value: "Value 11"), 
      CellData(title: "Cell Title 12", value: "Value 12"), 
      CellData(title: "Cell Title 13", value: "Value 13"), 
      CellData(title: "Cell Title 14", value: "Value 14"), 
      CellData(title: "Cell Title 15", value: "Value 15"), 
      CellData(title: "Cell Title 16", value: "Value 16"), 
      CellData(title: "Cell Title 17", value: "Value 17"), 
      CellData(title: "Cell Title 18", value: "Value 18")] 

     self.collectionView.registerNib(UINib(nibName: "CollectionCell", bundle: nil), forCellWithReuseIdentifier: "CollectionCell") 

     self.collectionView.registerNib(UINib(nibName: "SectionHeader", bundle: nil), forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "SectionHeader") 

     self.collectionView.registerNib(UINib(nibName: "SectionFooter", bundle: nil), forSupplementaryViewOfKind: UICollectionElementKindSectionFooter, withReuseIdentifier: "SectionFooter") 
    } 

    @IBAction func reload() { 
     self.activityIndicator.center = self.view.center 
     self.view.addSubview(self.activityIndicator) 
     self.activityIndicator.startAnimating() 
     self.view.userInteractionEnabled = false 

     let waitTime = 2 * Double(NSEC_PER_SEC) 
     let dispatchTime = dispatch_time(dispatch_time_t(DISPATCH_TIME_NOW), Int64(waitTime)) 
     dispatch_after(dispatchTime, dispatch_get_main_queue()) { 
      self.reloadIndex += 1 

      if self.reloadIndex > 3 { 
       self.reloadIndex = 1 
      } 
      switch self.reloadIndex { 
      case 2: 
       self.data = self.data2 
       break 
      case 3: 
       self.data = self.data3 
       break 
      default: 
       self.data = self.data1 
      } 
      self.collectionView.reloadSections(NSIndexSet(index: 0)) 
      //self.collectionView.reloadData() 

      self.activityIndicator.stopAnimating() 
      self.activityIndicator.removeFromSuperview() 
      self.view.userInteractionEnabled = true 
     } 
    } 

    @IBAction func print() { 
     printViewHierarchyInJSON(self.view) 
    } 

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

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

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell { 

     let compatibleCell = collectionView.dequeueReusableCellWithReuseIdentifier("CollectionCell", forIndexPath: indexPath) 
     (compatibleCell as? CollectionCell)?.setData(self.data[indexPath.item]) 
     return compatibleCell 
    } 

    func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView { 

     var supplementaryView = UICollectionReusableView() 

     switch kind { 
     case UICollectionElementKindSectionHeader: 
      supplementaryView = collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionHeader, withReuseIdentifier: "SectionHeader", forIndexPath: indexPath) 

     case UICollectionElementKindSectionFooter: 
      supplementaryView = collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionFooter, withReuseIdentifier: "SectionFooter", forIndexPath: indexPath) 

     default: 
      break 
     } 

     return supplementaryView 
    } 


    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize { 
     return CGSizeMake(collectionView.bounds.size.width, 50) 
    } 

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize { 
     return CGSizeMake(collectionView.bounds.size.width, 104) 
    } 

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize { 
     return CGSizeMake(collectionView.bounds.size.width, 86) 
    } 
} 

我已经上传此示例应用程序上dropbox。

预先感谢您。

Answer 1

因为每次重新加载不同的元素集合时间：

 self.reloadIndex += 1 

     if self.reloadIndex > 3 { 
      self.reloadIndex = 1 
     } 
     switch self.reloadIndex { 
     case 2: 
      self.data = self.data2 
      break 
     case 3: 
      self.data = self.data3 
      break 
     default: 
      self.data = self.data1 
     }