如何使用重新加载项目而不是使用firestore重新加载所有数据

Question

我有一个使用 Firestore 的聊天应用程序，当一个新的 document or -> (message) 添加到 Firestore 时，我的 collectionView 重新加载所有数据，应用程序冻结一秒钟，直到所有数据重新加载，我不太了解collectionViews 但我认为如果没有错，这是因为 collectionView 试图计算每个单元格的大小，这是调试器消息

The relevant UICollectionViewFlowLayout instance is <UICollectionViewFlowLayout: 0x7fbd974b3c40>, and it is attached to <UICollectionView: 0x7fbd97930600; frame = (0 61; 414 663); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x600002c5df20>; layer = <CALayer: 0x6000023f9640>; contentOffset: {-5, -5}; contentSize: {404, 8}; adjustedContentInset: {5, 5, 5, 5}; layout: <UICollectionViewFlowLayout: 0x7fbd974b3c40>; dataSource: <DELEVARE___ديليفري.DriverChat: 0x7fbd97843600>>.
2021-01-16 13:54:43.232052+0200 DELEVARE - ديليفري[51104:999159] Make a symbolic breakpoint at UICollectionViewFlowLayoutBreakForInvalidSizes to catch this in the debugger.

symbolic breakpoint at UICollectionViewFlowLayoutBreakForInvalidSizes to catch this in the debugger.

这个调试器消息被调用repeated，每个单元格都加载到collectionView，这是我的collectionView How to solve UICollectionViewFlowLayoutBreakForInvalidSizes

我不知道如何只将新的附加项插入到 collectionView 中的数组中，我希望它能够像普通聊天应用一样做出反应。

我试过了

func getMessages(){
        guard let uid = Auth.auth().currentUser?.uid else {return}
        
        let firestore = Firestore.firestore()
        let doc = firestore.collection("طلبات قيد العمل").whereField("driverUid", isEqualTo: uid)
        doc.getDocuments { (query, err) in
            if err != nil {
                print(err?.localizedDescription ?? "")
            }
            for document in query!.documents{

                let chatDoc = document.reference.collection("المحادثات")

                chatDoc.addSnapshotListener { (querysnap, err) in
                    if err != nil {
                        print(err?.localizedDescription ?? "")
                    }
                    self.messages = []
                    for snap in querysnap!.documents{
                    
                    let data = snap.data()
                    guard let message = data["message"] as? String else {return}
                    guard let senderid = data["senderID"] as? String else {return}
                    guard let timestamp = data["date"] as? Timestamp else {return}
                    let date = Date(timeIntervalSince1970: TimeInterval(timestamp.seconds))
                    if senderid == Auth.auth().currentUser?.uid{
                        let drivermessages = driverMessages(image: UIImage(), text: message, date: date, isSender: true, driverid: senderid)

                        // this line of code is doing the same as collectionView.reloadData()

                        self.collectionView?.performBatchUpdates({
                            let indexPath = IndexPath(row: self.comments.count, section: 0)
                            self.messages.append(drivermessages)
                            self.collectionView?.insertItems(at: [indexPath])
                        }, completion: nil)
                        
                    }else {
                        
                        guard let message2 = data["message"] as? String else {return}
                        guard let senderid2 = data["senderID"] as? String else {return}
                        guard let timestamp2 = data["date"] as? Timestamp else {return}
                        guard let img = self.profileImg else {return}
                        let date2 = Date(timeIntervalSince1970: TimeInterval(timestamp2.seconds))
                        
                        let usermessages = driverMessages(image: img, text: message2, date: date2, isSender: false, driverid: senderid2)
                        self.messages.append(usermessages)
                        
                        self.collectionView?.performBatchUpdates({
                            let indexPath = IndexPath(row: self.comments.count, section: 0)
                            self.messages.append(usermessages)
                            self.collectionView?.insertItems(at: [indexPath])
                        }, completion: nil)
                        
                        }
                            
                     }
                 }
                
             }
         }
      }

这是我的代码

func getMessages(){
        guard let uid = Auth.auth().currentUser?.uid else {return}

        
        let firestore = Firestore.firestore()
        let doc = firestore.collection("طلبات قيد العمل").whereField("driverUid", isEqualTo: uid)
        doc.getDocuments { (query, err) in
            if err != nil {
                print(err?.localizedDescription ?? "")
            }
            for document in query!.documents{
                let chatDoc = document.reference.collection("المحادثات")

                chatDoc.addSnapshotListener { (querysnap, err) in
                    if err != nil {
                        print(err?.localizedDescription ?? "")
                    }
                    self.messages = []
                    for snap in querysnap!.documents{
                    
                    let data = snap.data()
                    guard let message = data["message"] as? String else {return}
                    guard let senderid = data["senderID"] as? String else {return}
                    guard let timestamp = data["date"] as? Timestamp else {return}
                    let date = Date(timeIntervalSince1970: TimeInterval(timestamp.seconds))
                    if senderid == Auth.auth().currentUser?.uid{
                        let drivermessages = driverMessages(image: UIImage(), text: message, date: date, isSender: true, driverid: senderid)
                        self.messages.append(drivermessages)
                        
                    }else {
                        
                        guard let message2 = data["message"] as? String else {return}
                        guard let senderid2 = data["senderID"] as? String else {return}
                        guard let timestamp2 = data["date"] as? Timestamp else {return}
                        guard let img = self.profileImg else {return}
                        let date2 = Date(timeIntervalSince1970: TimeInterval(timestamp2.seconds))
                        
                        let usermessages = driverMessages(image: img, text: message2, date: date2, isSender: false, driverid: senderid2)
                        self.messages.append(usermessages)
                        
                        }
                        DispatchQueue.main.async {
                            self.collectionView.reloadData()
                            let item = self.messages.count - 1
                            let insertionIndexPath = IndexPath(item: item, section: 0)
                            self.collectionView.scrollToItem(at: insertionIndexPath, at: .bottom, animated: true)
                        }
                            
                     }
                 }
                
             }
         }
      }

Answer 1

我对自己编码非常陌生。 但是，在我看来，可以帮助您的事情是让.onSnapshot 侦听器寻找change 类型为added。

https://firebase.google.com/docs/reference/android/com/google/firebase/firestore/DocumentChange.Type

我发现这篇文章对我正在开发的 CRUD 应用程序很有帮助：

https://bezkoder.com/react-hooks-firestore/

其中一部分展示了如何监听各种类型的变化。 我能够在我的应用程序中实现它以仅返回添加的文档而不是整个集合，然后将其附加到我的数组中。

   tutorialsRef.onSnapshot(function(snapshot) {
  snapshot.docChanges().forEach(function(change) {
    if (change.type === "added") {
      console.log("New tutorial: ", change.doc.data());
    }
    if (change.type === "modified") {
      console.log("Modified tutorial: ", change.doc.data());
    }
    if (change.type === "removed") {
      console.log("Removed tutorial: ", change.doc.data());
    }
  });
});