I am trying to query my Messages table for three things. The first is any messages with that involve the current user logged in. Then, I want to get the user id of the person the current user has a coversation with. And finally, I want to check if any of the messages were seen. But right now my query only runs the first and last queries and not the second one. But I don't know why.
FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
DatabaseReference dbRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference userMessageKeyRef = dbRef.child("Messages").child(firebaseUser.getUid());
userMessageKeyRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
for (DataSnapshot snapshot1 : snapshot.getChildren()) {
String messageToID = snapshot1.getKey();
DatabaseReference messageRef = dbRef.child("Messages").child(firebaseUser.getUid()).child(messageToID);
Query query = messageRef.orderByChild("to").equalTo(firebaseUser.getUid());
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
long count = dataSnapshot.getChildrenCount();
if (dataSnapshot.exists()) {
DatabaseReference messageKeyRef = dbRef.child("Messages").child(firebaseUser.getUid()).child(messageToID);
Query query2 = messageKeyRef.orderByChild("isSeen").equalTo(false);
query2.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataShot) {
if (dataShot.exists() && count > 0) {
//Log.d("TAG2", "count if: " + count2);
messages_text.setText("" + Math.toIntExact(count));
messages_text.setVisibility(View.VISIBLE);
} else {
messages_text.setVisibility(View.GONE);
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
} else {
messages_text.setVisibility(View.GONE);
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
//Log.d("TAG1", "User to: " + messageToID);
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
Your first addValueEventListener already loads all data for the current user, so there is no need to go back to the database to load that data again. Instead you should check the properties of each message in your application code with something like:
DatabaseReference userMessageKeyRef = dbRef.child("Messages").child(firebaseUser.getUid());
userMessageKeyRef.addValueEventListener(new ValueEventListener() {
for (DataSnapshot parentSnapshot : snapshot.getChildren()) {
for (DataSnapshot messageSnapshot : addValueEventListener.getChildren()) {
String messageToID = messageSnapshot.getKey();
String toValue = messageSnapshot.child("to").getValue(String.class);
Boolean isSeenValue = messageSnapshot.child("isSeen").getValue(Boolean.class);
if (toValue.equals(firebaseUser.getUid()) && isSeenValue == true) {
...
}
}
}
});
Related
I am trying to select data from my database and I want to check if a specific child node has a one or a zero as it's value. If it has a 1 then I don't want to show info from that specific user. If it has a zero then I want to show info from that specific user.
I did it in a method above the one I'm working on(I followed this answer How to get child of child value from firebase in android?) and I got it working no problem. But I can't do the same for my other method and I have been trying all day now.
As of right now, the only result I am getting is the list not showing up at all. Can someone please help me ?
Method that works:
private void getPosts() {
followingList = new ArrayList<>();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Video_Posts");
FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
myPosts.clear();
//followingList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
Post post = snapshot.getValue(Post.class);
if (followingList.isEmpty()) {
if (!post.getPublisher().equals(firebaseUser.getUid())) {
DatabaseReference zonesRef = FirebaseDatabase.getInstance().getReference("Users");
DatabaseReference zone1Ref = zonesRef.child(post.getPublisher());
DatabaseReference zone1NameRef = zone1Ref.child("acc_closed");
zone1NameRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
//Log.i(TAG, dataSnapshot.getValue(String.class));
if (dataSnapshot.getValue(String.class).equals("1")) {
//Toast.makeText(getContext(), "Account closed", Toast.LENGTH_SHORT).show();
} else if (dataSnapshot.getValue(String.class).equals("0")) {
//Toast.makeText(getContext(), "Not closed.", Toast.LENGTH_SHORT).show();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
Query query = rootRef
.child("Follow")
.child(firebaseUser.getUid())
.child("following")
.child(post.getPublisher());
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
//Do something
Toast.makeText(getContext(), "Following.", Toast.LENGTH_SHORT).show();
} else {
//Do something else
myPosts.add(post);
Collections.shuffle(myPosts);
//Toast.makeText(getContext(), "Something.", Toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
};
query.addListenerForSingleValueEvent(valueEventListener);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
//Log.w(TAG, "onCancelled", databaseError.toException());
}
});
} else if (myPosts == null) {
Toast.makeText(getContext(), "Nothing.", Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(getContext(), "List is not empty.", Toast.LENGTH_SHORT).show();
for (String id : followingList) {
assert post != null;
if (!post.getPublisher().equals(id)) {
myPosts.add(post);
Toast.makeText(getContext(), "Something.", Toast.LENGTH_SHORT).show();
} else if (myPosts == null) {
Toast.makeText(getContext(), "Nothing.", Toast.LENGTH_SHORT).show();
}
}
}
}
adapterExplorer.notifyDataSetChanged();
progressBar.setVisibility(View.GONE);
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
}
Method that doesn't work:
private void searchUsers(String s) {
Query query = FirebaseDatabase.getInstance().getReference("Users");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (search_bar.getText().toString().equals("")) {
recyclerView.setVisibility(View.INVISIBLE);
}
mUsers.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
User user = snapshot.getValue(User.class);
DatabaseReference zonesRef = FirebaseDatabase.getInstance().getReference("Users");
DatabaseReference zone1Ref = zonesRef.child(user.getId());
DatabaseReference zone1NameRef = zone1Ref.child(user.getAcc_closed());
//mUsers.add(user);
zone1NameRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapS) {
if (snapS.getKey().equals("1")) {
} else if (snapS.getKey().equals("0")){
//if (!snapS.exists()) {
Log.d("TAG", snapS.toString());
mUsers.add(user);
//}
}
//}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
Log.d("Error name", error.getMessage());
}
});
}
userAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
Log.d("Error name", error.getMessage());
}
});
}
Database:
"Users": {
"4mFQt8Lf3CTNrQF74sy8wwyFoLh1": {
"acc_closed": "0",
"bio": "",
"dateAdded": "19-06-2022 17:28:56",
"date_time": 1655674136805,
"device_token": "feGjHNzaR7S8yaV2HKg0rt:APA91bEXAiYwT52niHVxR2ENrcaKXSNs11Z5ss-g2gsDwTs4wbjqjcrN4ZUmemqiMzp6SZM6UXD5TFrc1JND_DoEgd-Ni9wMeCa73EzvKBAaj5aXJf1GjgjSsTVwBg1A6VvhvVwF1VSX",
"fullname": "Brandon",
"id": "4mFQt8Lf3CTNrQF74sy8wwyFoLh1",
"imageurl": "https://firebasestorage.googleapis.com/v0/b/gone-b14f5.appspot.com/o/default.jpg?alt=media&token=befece91-9248-45ee-ab6f-b1b3d217c6b4",
"username": "bran1",
"verified": "false"
},
EDIT:
The code above (searchUsers) kind of works. When I put text into the search bar nothing shows up. But when I hit the back button and remove the keyboard the data shows up. It's like I'm actually waiting for data to change.
The simple fix is that you should call notifyDataSetChanged after you modified the data that the adapter shows, where right now you're calling it before that.
So move the call to userAdapter.notifyDataSetChanged() to right after mUsers.add(user):
Query query = FirebaseDatabase.getInstance().getReference("Users");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (search_bar.getText().toString().equals("")) {
recyclerView.setVisibility(View.INVISIBLE);
}
mUsers.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
User user = snapshot.getValue(User.class);
DatabaseReference zonesRef = FirebaseDatabase.getInstance().getReference("Users");
DatabaseReference zone1Ref = zonesRef.child(user.getId());
DatabaseReference zone1NameRef = zone1Ref.child(user.getAcc_closed());
zone1NameRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapS) {
if (snapS.getKey().equals("1")) {
} else if (snapS.getKey().equals("0")){
Log.d("TAG", snapS.toString());
mUsers.add(user);
userAdapter.notifyDataSetChanged(); // 👈
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
Log.d("Error name", error.getMessage());
}
});
}
}
There is some more (but not related to the problem) room for optimization here, as the dataSnapshot you get in the outermost listener already contains the data for *alldata under/Users`.
So there's no need to add an other listener to get the acc_closed value for each user. Instead you can just navigate the initial snapshot like this:
Query query = FirebaseDatabase.getInstance().getReference("Users");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (search_bar.getText().toString().equals("")) {
recyclerView.setVisibility(View.INVISIBLE);
}
mUsers.clear();
for (DataSnapshot userSnapshot : dataSnapshot.getChildren()) {
DataSnapshot snapS = userSnapshot.child("acc_closed");
String accClose = snapS.getValue(String.class)
if (accClose.equals("0")){
Log.d("TAG", accClose);
mUsers.add(userSnapshot.getValue(User.class));
userAdapter.notifyDataSetChanged();
}
}
}
Finally: your code retrieves all /Users to then only use the users who have acc_close being equal to "0". This wastes (your and your user's) bandwidth, especially as you're adding more users. It's much better to use a query to retrieve only the necessary data from the server/database:
DatabaseReference usersRef = FirebaseDatabase.getInstance().getReference("Users");
Query query = usersRef.orderByChild("acc_closed").equalTo("0");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (search_bar.getText().toString().equals("")) {
recyclerView.setVisibility(View.INVISIBLE);
}
mUsers.clear();
for (DataSnapshot userSnapshot : dataSnapshot.getChildren()) {
mUsers.add(userSnapshot.getValue(User.class));
}
userAdapter.notifyDataSetChanged();
}
I want to change the value of child "toggleStatus" under Reference "BetSlip" as shown below. The already set value is "on" so I want such that when I click the button the value of "toggleStatus" is changed to "off"
BetSlipActivity.toggleCollapse.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String timeStamp = betSlip.get(position).getTimeStamp();
String toggleStatus = betSlip.get(position).getToggleStatus();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("BetSlip");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
for (DataSnapshot ds: snapshot.getChildren()) {
String timestamp = ""+ ds.child("timeStamp").getValue();
String toggleStatus = ""+ ds.child("toggleStatus").getValue();
if (timeStamp.equals(timestamp) && toggleStatus.equals("on")) {
//set value to off
}
if (timeStamp.equals(timestamp) && toggleStatus.equals("off")) {
//set value to on
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
}
});
If you've got the DataSnapshot for a path in the database, it's easy to get the DatabaseReference that you need to update it:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("BetSlip");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
for (DataSnapshot ds: snapshot.getChildren()) {
String timestamp = ""+ ds.child("timeStamp").getValue();
String toggleStatus = ""+ ds.child("toggleStatus").getValue();
if (timeStamp.equals(timestamp) && toggleStatus.equals("on")) {
ds.child("toggleStatus").getRef().setValue("off");
}
if (timeStamp.equals(timestamp) && toggleStatus.equals("off")) {
ds.child("toggleStatus").getRef().setValue("on");
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
throw error.toException(); // never ignore errors
}
});
Since you're updating the node based on its existing value, strictly speaking you might need to use a transaction for it.
So basically I made a String mojID which is equal to firebase's current user, I want to pass it as a child in a node but it says it is a null pointer exception and I have already used it in another parts of a code which does not return the fault.
I am attaching some of my code.
final DatabaseReference chatRef1 = FirebaseDatabase.getInstance().getReference("ChatLista");
chatRef1.child(mojID);
chatRef1.child(userID);
chatRef1.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if(!dataSnapshot.exists()){
chatRef1.child("id").setValue(userID);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
final DatabaseReference chatRef2 = FirebaseDatabase.getInstance().getReference("ChatLista");
chatRef2.child(userID);
chatRef2.child(mojID);
chatRef2.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if(!dataSnapshot.exists()){
chatRef2.child("id").setValue(mojID);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Then there is function that takes the ID:
private void ProvjeriStatus(){
FirebaseUser user = firebaseAuth.getCurrentUser();
if(user!=null){
//user ulogovan
mojID = (String)user.getUid();
}
//ako nije vraca na login
else {
startActivity(new Intent(this,login.class));
finish();
}
}
I even tried casting it as you can see it and it just says I don't need a cast, because it is already a String? Then why does it return null? The only explanation I have come up with is that it is an object not a string and by that .child wants a string as a argument not an object.
You can add UserId via FirebaseUser.. You can refer Below code .. maybe it will help
you
FirebaseUser currentFirebaseUser;
DatabaseReference databaseReference;
currentFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();
databaseReference = FirebaseDatabase.getInstance().getReference();
databaseReference.child("Users").child(currentFirebaseUser.getUid()).child("User
Id").setValue(currentFirebaseUser.getUid());
If you want to retrieve UserId from database Refer Below code..
DatabaseReference myRef = database.getReference("Users");
myRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if ((dataSnapshot.child(currentFirebaseUser.getUid()).child("UserId").getValue() == null)) {
databaseReference.child("Users").child(currentFirebaseUser.getUid())
.child("UserId").setValue(currentFirebaseUser.getUid());
} else {
String Id= (String) dataSnapshot.child(currentFirebaseUser.getUid()).child("UserId").getValue();
}
I want to read some specific child from the parent-child, by getchild() function but this will not work properly.
FirebaseUser FUser = mAuth.getCurrentUser();
String userid = FUser.getUid();
DatabaseReference DR;
DR = FirebaseDatabase.getInstance().getReference().child("HistoryTable").child(userid);
DR.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
// Iterable<DataSnapshot> root = dataSnapshot.getChildren();
// Toast.makeText(getApplicationContext(), "ds "+dataSnapshot.getChildren(),Toast.LENGTH_LONG).show();
for (DataSnapshot ds: dataSnapshot.getChildren()) {
// Toast.makeText(getApplicationContext(), "ds "+ds,Toast.LENGTH_LONG).show();
for (DataSnapshot d: ds.getChildren()) {
String Height = d.getKey() + d.getValue() + "\n".toString();
String ch = d.child("1Height:").getValue(String.class);
// tv.append(Height);
tv.append(ch);
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
I want to get this four child from every key.
you have to add your push id in reference :-
DR = FirebaseDatabase.getInstance().getReference().child("HistoryTable").child(userid).child("push id");
DR.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
// Iterable<DataSnapshot> root = dataSnapshot.getChildren();
// Toast.makeText(getApplicationContext(), "ds "+dataSnapshot.getChildren(),Toast.LENGTH_LONG).show();
for (DataSnapshot ds: dataSnapshot.getChildren()) {
// Toast.makeText(getApplicationContext(), "ds "+ds,Toast.LENGTH_LONG).show();
for (DataSnapshot d: ds.getChildren()) {
String Height = d.getKey() + d.getValue() + "\n".toString();
String ch = d.child("1Height:").getValue(String.class);
// tv.append(Height);
tv.append(ch);
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Try like this if you just want to read the value. if you want to read data only once use addListenerForSingleValueEvent()
*Try to read values by object stucture https://firebase.google.com/docs/database/android/read-and-write#basic_write
DR.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot d: ds.getChildren()) {
//below line may cause null pointer Exception
String Height = d.getKey() + d.getValue() + "\n".toString();
if(d.child("1Height:").getValue()!=null){
String ch = d.child("1Height:").getValue(String.class);
//tv.append(Height);
tv.append(ch);}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
To get the value of your 4UserId property, simply use the following lines of code:
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference uidRef = rootRef.child("HistoryTable").child(uid);
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String userId = ds.child("4UserId").getValue(String.class);
Log.d(TAG, userId);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
uidRef.addListenerForSingleValueEvent(valueEventListener);
The result in your logcat will be:
2Wwrjx...P2obFO83
DatabaseReference newReferance = database.getReference().child("Users");
Query query = newReferance.orderByChild("timestamp");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
chatMessages.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
HashMap<String, String> hashMap = (HashMap<String, String>) dataSnapshot1.getValue();
//String userMail = hashMap.get("useremail");
String userMessage = hashMap.get("usermessage");
String userCt = hashMap.get("usershow");
chatMessages.add(userCt + ": " + userMessage);
if (chatMessages.size() >= 10){
for (int i= 0; i < 5; i++){
//HOW ????
}
}
recyclerAdapter.notifyDataSetChanged();
}
}
Hi Dear guys. How do I select and delete the first 5 data in a real-time database? When the ArrayList reaches a certain limit, I want to delete the first 5 data from the database. I'd appreciate it if you could help with the problem.
How do I select and delete the first 5 data in a real-time database?
You can achieve this using Firebase Query's limitToFirst(int limit):
Create a query with limit and anchor it to the start of the window
And in code should look like this:
Query query = newReferance.orderByChild("timestamp").limitToFirst(5);
See I have used this limitToFirst() method that can help you find the first 5 items. To delete them, just attach a listener and inside the onDataChange() method use the following line of code:
dataSnapshot.getRef().removeValue();
final DatabaseReference newReferance = database.getReference().child("Users");
final Query query = newReferance.orderByChild("timestamp");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
chatMessages.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
HashMap<String, String> hashMap = (HashMap<String, String>) dataSnapshot1.getValue();
//String userMail = hashMap.get("useremail");
String userMessage = hashMap.get("usermessage");
String userCt = hashMap.get("usershow");
chatMessages.add(userCt + ": " + userMessage);
if (chatMessages.size() >= 10){
Query query1 = newReferance.limitToFirst(5);
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
database.getReference().child("Users").setValue(null);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
recyclerAdapter.notifyDataSetChanged();
}
}
Although I'm set, it's all deleted. I can't erase the items I want. All cleared.
rootRef is the firebase database reference. whose instance we have to gained before trying to delete any value. you can see the code given below.
count = 0;
rootRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
for (DataSnapshot postSnapshot : snapshot.getChildren()) {
CommonLocationClass user = postSnapshot.getValue(CommonLocationClass.class);
if (count < 5) {
rootRef.child(user.getPhNo).removeValue();
count++;
}
}
}
}
#Override
public void onCancelled (DatabaseError firebaseError){
}
});
the CommonLocationClass is a getter setter model class i have made to make the fire-base implementation easy
you can try this it works for me
public void getDataFirebase() {
/*if (chatMessages.size() == MAX_MSJ_LIMIT){
database.getReference().child("Users").removeValue();
}*/
final DatabaseReference newRefere = database.getReference().child("Users");
Query query = newRefere.orderByChild("timestamp");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
chatMessages.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
HashMap<String, String> hashMap = (HashMap<String, String>) dataSnapshot1.getValue();
//String userMail = hashMap.get("useremail");
String userMessage = hashMap.get("usermessage");
String userCt = hashMap.get("usershow");
chatMessages.add(userCt + ": " + userMessage);
recyclerAdapter.notifyDataSetChanged();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(getApplicationContext(), databaseError.getMessage(), Toast.LENGTH_LONG).show();
}
});
if (chatMessages.size() >= 10) {
Query query1 = newRefere.orderByChild("timestamp").limitToFirst(5);
query1.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
dataSnapshot.getRef().removeValue();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
}
It didn't just erase the first 5 data.
if (chatMessages.size() >= 10) {
Query query1 = newRefere.orderByChild("timestamp").limitToFirst(5);
query1.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()){
ds.getRef().removeValue();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
I solved the problem. With this code