Swift 3.0 中的 UICollectionViewController 错误：必须使用非零布局参数进行初始化

我是 iOS 开发新手。 我一直在学习 Swift，今天，我尝试使用 UICollectionViewController。

我的代码如下：

 class ViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
    var colView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 20, left: 10, bottom: 10, right: 10)
        layout.itemSize = CGSize(width: 90, height: 120)

        colView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
        colView.dataSource = self
        colView.delegate = self
        colView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
        colView.backgroundColor = UIColor.white
        self.view.addSubview(colView)
    }

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 14
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath as IndexPath)
        cell.backgroundColor = UIColor.orange
        return cell
    }


}

但是，当我尝试运行它时，出现以下错误：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'UICollectionView must be initialized with a non-nil layout parameter'

我查阅了之前讨论此问题的帖子，但找不到任何可以修复我的代码的内容。

我应该如何解决这个问题？

谢谢你！我采纳了你的建议。下面是有效的代码：

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    let cellId = "CellId"
    var colView: UICollectionView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let layout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 20, left: 10, bottom: 10, right: 10)
        layout.itemSize = CGSize(width: 111, height: 111)
        
        colView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
        colView.delegate   = self
        colView.dataSource = self
        colView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
        colView.backgroundColor = UIColor.white
        
        self.view.addSubview(colView)
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 21
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath as IndexPath)
        cell.backgroundColor = UIColor.orange
        return cell
    }
}

再次非常感谢你们。祝你有美好的一天:D