可能当你展示你的 ChatViewController 时，你会有类似的东西:

Probably when you present your ChatViewController you have something like:

让 chatVC = ChatViewController()

let chatVC = ChatViewController()

但根据 Apple 文档:

类 UICollectionViewController

当您初始化控制器时，使用 init(collectionViewLayout:) 方法，您指定集合视图应该具有的布局.

When you initialize the controller, using the init(collectionViewLayout:) method, you specify the layout the collection view should have.

所以你需要:

 let chatVC = ChatViewController(collectionViewLayout: UICollectionViewFlowLayout())