问题描述
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());
}
以下是我如何开始使用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();
1楼
为了将您的文档转换为类，请使用：
Message message = documentSnapshot.toObject(Message.class);
如这里解释：
DocumentReference docRef = db.collection("cities").document("BJ");
docRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
@Override
public void onSuccess(DocumentSnapshot documentSnapshot) {
City city = documentSnapshot.toObject(City.class);
}
});
更新：-您可以在代码中将其用作：-
firestore = FirebaseFirestore.getInstance();
firestore.collection(mRoomID + "_messages")
.addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(@Nullable QuerySnapshot snapshots,
@Nullable FirebaseFirestoreException e) {
for (DocumentChange dc : snapshots.getDocumentChanges()) {
switch (dc.getType()) {
case ADDED:
Message message = snapshots.toObject(Message.class);
break;
}
}
}
});