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我的要求是在 ViewController 中的视图之上有一个滑块集合视图。我已经尝试了很多解决方法来满足我的要求（您可以在我的集合视图设置代码中看到）。但是，当我收到关于The behavior of the UICollectionViewFlowLayout is not defined. 视图控制器是从控制器数组中调用的，而控制器数组UITabBarController又嵌入在UINavigtionController. 视图控制器包含一个高度为 200 的集合视图。我希望​​集合视图的每个单元格都扩展其完整的宽度和高度。

警告：

2017-09-06 12:05:19.139 collectionViewSample[3686:79491] The behavior of the UICollectionViewFlowLayout is not defined because:
2017-09-06 12:05:19.139 collectionViewSample[3686:79491] the item height must be less than the height of the UICollectionView minus the section insets top and bottom values, minus the content insets top and bottom values.
2017-09-06 12:05:19.140 collectionViewSample[3686:79491] The relevant UICollectionViewFlowLayout instance is <UICollectionViewFlowLayout: 0x7ff4e4c00020>, and it is attached to <UICollectionView: 0x7ff4e5032600; frame = (0 64; 414 200); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x600000047290>; layer = <CALayer: 0x60000002d240>; contentOffset: {0, -64}; contentSize: {0, 0}> collection view layout: <UICollectionViewFlowLayout: 0x7ff4e4c00020>.
2017-09-06 12:05:19.140 collectionViewSample[3686:79491] Make a symbolic breakpoint at UICollectionViewFlowLayoutBreakForInvalidSizes to catch this in the debugger.

应用委托：

    window = UIWindow(frame: UIScreen.main.bounds)
    window?.makeKeyAndVisible()
    let mainController = UITabBarController()
    let navController = UINavigationController(rootViewController: ViewController())
    mainController.viewControllers = [navController]
    window?.rootViewController = mainController

视图控制器：

class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

override func viewDidLoad() {
    super.viewDidLoad()

    view.backgroundColor = .white
    setupCollectionView()
}

func setupCollectionView() {

    let layout = UICollectionViewFlowLayout()
    layout.scrollDirection = .horizontal
    let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
    collectionView.translatesAutoresizingMaskIntoConstraints = false
    collectionView.scrollIndicatorInsets = .zero
    collectionView.contentInset = .zero
    collectionView.preservesSuperviewLayoutMargins = false
    collectionView.layoutMargins = .zero

    collectionView.delegate = self
    collectionView.dataSource = self
    collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "cellId")
    view.addSubview(collectionView)

    collectionView.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor).isActive = true
    collectionView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
    collectionView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
    collectionView.heightAnchor.constraint(equalToConstant: 200).isActive = true
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath)
    cell.backgroundColor = .green
    return cell
}

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 2
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return 0
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
    return 0
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
    return UIEdgeInsetsMake(0, 0, 0, 0)
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    return CGSize(width: view.frame.width, height: 200)
}
}

当单元格填充了填充集合视图的整个框架的图像时，它会在导航栏的顶部留下一个小间隙。集合视图框架确实扩展到我的要求，但单元格没有。我将如何以正确的方式解决这个问题？

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