Question

我正在尝试将我的实时数据库调整为适合聊天应用程序的Cloud Firestore。要存储的对象属于我创建的Message类。我希望邮件成为文档。

我的RecyclerView适配器将使用实时数据库像这样检索它们：

public ChatRecyclerViewAdapter(Context mContext, ArrayList<String> mMessage, ArrayList<String> mAuthor, String mRoomID,DatabaseReference reference) {

    this.mContext = mContext;
    this.mRoomID = mRoomID;

    mDatabaseReference = reference.child(mRoomID+"_messages");
    recentMessages = mDatabaseReference.orderByKey().limitToLast(numberOfRecentMessages);
    recentMessages.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
            // Convert data snapshot from Database into a Message Object

            Message message = dataSnapshot.getValue(Message.class);

            // Add it to an arrayList of Messages
            messageList.add(message);

            // Notice Changes
            notifyItemInserted(messageList.size());
        }

下面是我如何开始使用Firestore重新创建它的方法。如何在快照侦听器的onEvent方法中将快照转换回Message？

public ChatRecyclerViewAdapter(Context mContext, ArrayList<String> mMessage, ArrayList<String> mAuthor, String mRoomID, FirebaseFirestore firestore, CollectionReference reference) {
    this.mContext = mContext;
    this.mRoomID = mRoomID;

        messageList = new ArrayList<>();
        firestore = FirebaseFirestore.getInstance();
        mCollection = firestore.collection(mRoomID + "_messages");
        mCollection.addSnapshotListener(new com.google.firebase.firestore.EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(@javax.annotation.Nullable QuerySnapshot queryDocumentSnapshots, @javax.annotation.Nullable FirebaseFirestoreException e) {
                for (DocumentChange documentChange:queryDocumentSnapshots.getDocumentChanges()){
                    switch (documentChange.getType()){
                        case ADDED:
                    }
                }
            }
        });
        mCollection.get();

Answer 1

为了将您的文档转换为类，请使用：-

if (!ModelState.IsValid)
{
    return BadRequest(ModelState);
}

如此处所述：-

ExceptionFilterAttribute

更新：- 您可以在代码中将其用作：-

Message message = documentSnapshot.toObject(Message.class);

如何从Cloud Firestore检索自定义对象？

1 个答案: