使用刷新重新加载集合视图

Question

我想刷新视图控制器中的数据。我使用重新加载数据，但它不起作用。我能做什么？请帮助我。我在标签栏控制器中有这个视图控制器。我试图从数组中删除所有元素 e 重用该功能，但我的元素翻了一番。我尝试使用viewwill出现，但是每次他返回Viewcontroller时，它都会添加很多相同的项目

override func viewDidLoad() {
super.viewDidLoad()
refreshControl.addTarget(self, action: #selector(HomeViewController.refreshData), for: UIControlEvents.valueChanged)
collectionview.addSubview(refreshControl)
lodPosts()
}
@objc func refreshData() {
refreshControl.endRefreshing()
}
func lodPosts() {
let ref = Database.database().reference()
ref.child("users").queryOrderedByKey().observeSingleEvent(of: .value, with: { snapshot in
let users = snapshot.value as! [String : AnyObject]
for(_,value) in users {
if let uid = value["uid"] as? String {
if uid == Auth.auth().currentUser?.uid {
if let followingUsers = value["following"] as? [String : String] {
for(_,user) in followingUsers {
self.following.append(user)
}
}
self.following.append(Auth.auth().currentUser!.uid)
ref.child("posts").queryOrderedByKey().observeSingleEvent(of: .value, with: { (snap) in
let postsSnap = snap.value as! [String: AnyObject]
for(_,post) in postsSnap {
if let userID = post["uid"] as? String {
for each in self.following {
if each == userID {
let posst = Post()
if let author = post["Author"] as? String, let likes = post["likes"] as? Int, let pathToImage = post["photoUrl"] as? String, let postID = post["postID"] as? String,let profileImage = post["profileImageUrl"] as? String,let caption = post["caption"] as? String {
posst.author = author
posst.likes = likes
posst.pathToImage = pathToImage
posst.postID = postID
posst.userID = userID
posst.userimage = profileImage
posst.caption = caption
self.posts.append(posst)
}
}
}
self.collectionview.reloadData()
}
}
})
}
}
}
})
}

Answer 1

所有 UI 操作都必须在主线程上执行

斯威夫特 4

DispatchQueue.main.async {
self.collectionview.reloadData()
}