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Firebase value not updating

Everything is working fine, I think just userDataModel.setUserRating(aFloat / (int) dataSnapshot.getChildrenCount()); is not giving value.
And String.valueof(aFloat / (int) dataSnapshot.getChildrenCount()));
Is also giving the correct value.
FirebaseDatabase.getInstance().getReference().child("Users").child(userDataModel.getUserID()).child("Ratings")
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
userDataModel1 = dataSnapshot.getValue(UserDataModel.class);
aFloat = aFloat + Float.parseFloat(Objects.requireNonNull(dataSnapshot1.getValue()).toString());
}
userDataModel.setUserRating(aFloat / (int) dataSnapshot.getChildrenCount());
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
UserDataModel
public class UserDataModel {
float userRating;
public float getUserRating() {
return userRating;
}
public void setUserRating(float userRating) {
this.userRating = userRating;
}
}
Image URL: https://i.stack.imgur.com/t14Cc.png

This is happening maybe because userDataModel.setUserRating(aFloat / (int) dataSnapshot.getChildrenCount()); is returning null so you don't get a value

The problem in your code us the fact that your UserDataModel has a field named userRating, while in your database the property is actually a uid. This property is dynamic, so you cannot use a POJO class for that. If you want to get the values of those ratings, please try this:
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference ratingsRef = rootRef.child("Users").child(uid).child("Ratings");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
double rating = ds.getValue(Double.class);
Log.d("TAG", "rating: " + rating);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d("TAG", databaseError.getMessage()); //Don't ignore errors!
}
};
ratingsRef.addListenerForSingleValueEvent(valueEventListener);
The output in the logcat will be values of all ratings that exist within the Ratings node.
3.5
2
Now, you can simply make the average or whatever you need with those values.

how to adding the all value from " price" node with diffrent parent in firebase [duplicate]

This question already has answers here:
Firebase Database retrieving sum of multiple childs
(2 answers)
Closed 3 years ago.
Database Structure
I am still new with android and Firebase stuff and I have encountered a few problems when trying to adding the value from node, the thing is, I want to add all value from "price" node, but I have problem where, every price node have different parent, and I don't know how to add all value with different parent
what i've already tried:
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
databaseReference = firebaseDatabase.getReference().child("mycart").child(ID).child(uid).child("quantity");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot dSnapshot : dataSnapshot.getChildren()) {
///...code
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
usersRef.addListenerForSingleValueEvent(eventListener);
}

To sum up all your prices from all the keys, you can do this:
databaseReference = firebaseDatabase.getReference().child("mycart").child(ID);
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
float price = 0;
for(Datasnapshot snapshot: datasnapshot.getChildren()){
price += snapshot.child("price").getValue(Float.class);
}
Log.d("Total: ", price);
}
#Override
public void onCancelled(DatabaseError databaseError) {
System.out.println("The read failed: " + databaseError.getCode());
}
});

Getting Data from Firebase realtime database, Android Studio, Java

I am looking for a way to get data from the firebase real-time database in a format like an array[] or a String.
My database looks like this:
Link to image of database
Or:
Database
|
-->Users
|
-->UID1
-->UID2
This is at the root of the database
I want to get a list of all of the UIDs in the "Users" child.
This is the code I have so far and am a bit stuck on:
DatabaseReference databaseReference = firebaseDatabase.getReference("Users");
databaseReference.addValueEventListener(
new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String UIDs = dataSnapshot.getValue(String.class);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
I am a bit of a rookie as it comes to java, android studio, and firebase. I am trying to get the data in a format I know how to use like a String or an Array[] of Strings. I looked around if other people had maybe asked the same question, but I could get the answers to those questions to work/didn't understand them.
Thanks in advance for your time!

To get the a list of uids, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = rootRef.child("Users");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> list = new ArrayList<>();
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String uid = ds.getKey();
list.add(uid);
}
//Do what you need to do with your list
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
usersRef.addListenerForSingleValueEvent(valueEventListener);
I recommend you to use the list only inside the callback otherwise it will be empty. If you want to use it outside the onDataChange() method, I recommend you see the last part of my anwser from this post in which I have explained how it can be done using a custom callback. You can also take a look at this video for a better understanding.

For your above question I will give both ways: ArrayList or String with delimiters
ArrayList<String> uids = new ArrayList<String>();
FirebaseDatabase.getInstance().getReference("Users").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for(DataSnapshot snapshot : dataSnapshot.getChildren()) {
uids.add(snapshot.getKey());
}
}
}
#Override
public void onCancelled(DatabaseError error) {
}
});
For String
String uids = "";
FirebaseDatabase.getInstance().getReference("Users").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for(DataSnapshot snapshot : dataSnapshot.getChildren()) {
uids += snapshot.getKey() + ",";
}
}
}
#Override
public void onCancelled(DatabaseError error) {
}
});
This gives an output such as: uid1,uid2,uid3,.....uidn,

You can try this:
DatabaseReference ref=
FirebaseDatabase.getInstance().getReference("Users");
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
int i = 0;
for(DataSnapshot d : dataSnapshot.getChildren()) {
name[i] = d.getKey();
i++;
}
}
}//onDataChange
#Override
public void onCancelled(DatabaseError error) {
}//onCancelled
});
name[] is an array of strings!

Firebase RealTime Database Delete First 20 item

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

how i can get my info through the random key by push

I have JsonString by receive DataSnapShot:
myRef.child("user").orderByChild("u_email").equalTo(name).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String c = dataSnapshot.getValue().toString();
Log.w(Login.TAG, "Data: "+ c);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
in normal if i know the key (-L3Mh7kKl04GSrndbrVD) ill code:
JSONObject a = new JSONObject(c);
JSONObject jsonUser = a.getJSONObject("-L3Mh7kKl04GSrndbrVD");
But i dont have that key, How i can get that value (name, pass, img, ...) with code, im newbie. Thanks all alot

try this:
DatabaseReference references=FirebaseDatabase.getInstance().getReference().child("user");
references.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot data: dataSnapshot.getChildren()){
String name=data.child("name").getValue().toString();
String password=data.child("pass").getValue().toString();
String img=data.child("img").getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Here the reference is the user node, then using the for loop it will iterate inside every push id to give you the values (name,img,pass,...).

Try this
myRef.child("user").orderByChild("u_email").equalTo(name).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String c = dataSnapshot.getValue().toString();
Log.w(Login.TAG, "Data: "+ c);
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String u_img = ds.child("u_img").getValue(String.class);
String u_pass = ds.child("u_pass").getValue(String.class);
String u_address = ds.child("u_address").getValue(String.class);
Log.d("TAG",u_img + " / " + u_pass + " / " + u_address);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});