Develop Reference

how to check the current Firebase data under uid?

I am trying to check uid from firebase Realtime database, but its only returns the current uid and when I try to check uid with previous uid then also it only returns the current uid. I had tried many ways and searched but I can't get the exact solution, please if any one could help.
here what I am using to check the uid
FirebaseAuth.getInstance().getCurrentUser().getUid();
here is my code how I am trying to check
String userEnteredUserName = binding.textLoginUserName.getEditText().getText().toString().trim();
String userEnteredPassword = binding.textPassword.getEditText().getText().toString().trim();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users");
Query checkUser = reference.child(FirebaseAuth.getInstance().getCurrentUser().getUid()).orderByChild("userName").equalTo(userEnteredUserName);
Log.d("uids", "uid: " + uid);
checkUser.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
binding.textLoginUserName.setError(null);
binding.textLoginUserName.setErrorEnabled(false);
Log.d("users", "Username: " + snapshot.toString());
if (snapshot.exists()) {
String passwordFromDB = snapshot.child(userEnteredUserName).child("password").getValue(String.class);
if (passwordFromDB.equals(userEnteredPassword)) {
//next activity
}else{
Toast.makeText(Login.this, "Error", Toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
Toast.makeText(Login.this, "Error", Toast.LENGTH_SHORT).show();
}
});
In log what I get,
2022-02-06 13:13:06.173 18093-18093/abc C/uids: uid: OFtpR6bfISP3Odd9K1oGWCQmeEf2
Here is my firebase data, "aisha12" is working which is under the current uid but when I try to check "vgbb" it returns only the current uid

If I understand correctly, you are trying to allow a user to register a username and ensuring that the username is unique. Your current data structure doesn't allow you to do that query though.
Firebase Realtime Database can only order/filter on a value that is at a fixed path under each child node of the location you query. So in your current code:
reference.child(FirebaseAuth.getInstance().getCurrentUser().getUid()).orderByChild("userName").equalTo(userEnteredUserName);
You are querying the direct child nodes of /Users/$uid looking for the username under there. Since you're specifying the UID in that path, you're only searching under that specific user.
There is no way with your current data structure to search across all /Users, since the property you are looking for is under /Users/$uid/$username/userName, so with two dynamic keys in there, and the database can only handle one dynamic key.
To allow the query, you will need to change the data structure and remove the $userName level from it, so that you get:
Users: {
"3l6Rm....": {
"userName": "vgbb",
...
},
"OftpR...": {
"userName": "aisha12",
...
}
}
Now you can search for the username with:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users");
Query checkUser = reference.orderByChild("userName").equalTo(userEnteredUserName);
I also recommend checking out these previous questions on allowing a user to register a unique username:
How do you prevent duplicate user properties in Firebase?
Firebase security rules to check unique value of a child #AskFirebase
How to check if usernames are unique in Firebase
unique property in Firebase
How to give unique usernames from a list of usernames to the users in the firebase
Check value already exists or not in Firebase?

Retrieve data from multiple push ids under a single child in firebase realtime database

I am new to android studio and programming and am currently trying to make my first app. In firebase RTDB, I have multiple push ids under a single child that keep on increasing in number as the user presses certain buttons, and they all store only an integer. I want to retrieve the data from all those push ids(or keys, I don't really know what they are actually called) under the child and then sum the integers up and display the result in a textView and do it every time a new field is added. How can I do that? So far I only know how to normally send and receive data to childs sub-childs like this but i have never ever used push ids or keys before:
String recieve = datasnapshot.child("Child").child("subchild").getText().toString();
String send = "send";
databaseReferenc.child("Child").child("sunchile").setValue(send);
The data tree in firebase is as follows:

Assuming that Australia is a direct child of your Firebase Realtime Database root, to sum all those values, please use the following lines of code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference australiaRef = rootRef.child("Australia");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int total = 0;
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String value = Integer.parseInt(ds.getValue(String.class));
total += value;
}
Log.d("TAG", "total: " + total);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d("TAG", databaseError.getMessage()); //Don't ignore potential errors!
}
};
australiaRef.addListenerForSingleValueEvent(valueEventListener);
One more thing. Because you are storing numbers, it best to store them as long values and not as String values.

How to retrieve and display data from users that are logged in - Firestore

I am trying to get and display my user's information when they are logged in. (i.e: name, email, phone)
I have tried multiple snippets i have found on youtube and on stack overflow but they have failed. Most tutorials use realtime Database, which is not what i am looking for.
I have also tried making a "users" object.
private void getData(){
FirebaseFirestore db = FirebaseFirestore.getInstance();
db.collection("users")
//.document(FirebaseAuth.getInstance().getCurrentUser().getUid())
.whereEqualTo("email:", FirebaseAuth.getInstance().getCurrentUser().getUid())
.get()
.addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
#Override
public void onComplete(#NonNull Task<QuerySnapshot> task) {
if (task.isSuccessful()) {
for (DocumentSnapshot document : task.getResult()) {
//Toast.makeText(getApplicationContext(),document.getId() +"==>" + document.getData(),Toast.LENGTH_LONG).show();
//Toast.makeText(getApplicationContext(),""+ document.get("Email") ,Toast.LENGTH_LONG).show();
nameEdt.setText((CharSequence) document.get("First Name"));
emailEdt.setText((CharSequence) document.get("Email"));
phoneEdt.setText((CharSequence) document.get("Phone"));
}
} else {
Toast.makeText(getApplicationContext(),"No such document",Toast.LENGTH_LONG).show();
}
}
});
}
Database Structure:
I understand that documents in firestore are not associated with users, but i dont know how to set my code up so that it only retrieves data from the user that is signed in* It works fine for newly created accounts, but if i were to log out and sign in with a different user it will not update the "account/user information".
In short, how would I access and display my database information from signed in users?
Additional Notes: I am using Email and Password for authentication

To access your user data stored in Firestore, it shouldn't be as complicated as you thought, there's no queries needed, you just need to fetch the documents corresponding to the user's uid, and fetch the specific fields or do whatever you need with them, like this:
db.collection("users").document(FirebaseAuth.getInstance().getCurrentUser().getUid())
.get().addOnCompleteListener(task -> {
if(task.isSuccessful() && task.getResult() != null){
String firstName = task.getResult().getString("First Name");
String email = task.getResult().getString("Email");
String phone = task.getResult().getString("Phone");
//other stuff
}else{
//deal with error
}
});
Original Answer:
User information is not stored in the Firestore database, they are associated with the Firebase Authentication which you set up for the log in. To retrieve the related user information, you need to use the related FirebaseAuth APIs. Use this to retrieve the current log in user:
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
Then you can get the name and email with something like this:
String name = user.getDisplayName();
String email = user.getEmail();
For more information, refer to the documentation.
If FirebaseAuth doesn't resolve, that probably means you didn't follow the set up guides correctly and forgot to include the dependency in your gradle file:
implementation 'com.google.firebase:firebase-auth:17.0.0'

After a couple days head butting at trying to find a solution, i have found one that is able to retrieve user information from the database. However it is important to note that because my application is not holding a lot of data so this structure works for me.
So i was essentially on the right track, but with some lack of understanding of firebase i missed a few concepts.
private void getData(){
FirebaseFirestore db = FirebaseFirestore.getInstance();
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
final String current = user.getUid();//getting unique user id
db.collection("users")
.whereEqualTo("uId",current)//looks for the corresponding value with the field
// in the database
.get()
.addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
#Override
public void onComplete(#NonNull Task<QuerySnapshot> task) {
if (task.isSuccessful()) {
for (DocumentSnapshot document : task.getResult()) {
nameEdt.setText((CharSequence) document.get("firstName"));
emailEdt.setText((CharSequence) document.get("email"));
phoneEdt.setText((CharSequence) document.get("phone"));
// These values must exactly match the fields you have in your db
}
}
As mentioned before, documents do not associate with users, but you CAN link them together by creating a field in your db called "whatever your want" (i made mine uId). This is because firebase generates a unique id for each user when authenticated. By creating a field that holds that unique id you are able to retrieve the associated information in that collection.
How to create the field:
I created a "user" object that would grab the uid from my edit text. In my code, i passed the uid wherever i was creating/authenticating a new user/account.
FirebaseUser testUser = FirebaseAuth.getInstance().getCurrentUser(); //getting the current logged in users id
String userUid = testUser.getUid();
String uidInput = userUid;
User user = new User(firstNameInput,lastNameInput,uidInput);
db.collection("users").document(userUid)
.set(user)
.addOnSuccessListener(new OnSuccessListener<Void>() {
note: I believe you can also add it to your hash map if you have it done that way.

Retrieving data from firebase node in android

I'm having trouble getting from my Firebase database data to an android app and the Firebase listener and data snapshot documentations aren't really helping.
Say I have a database with the nodes structured as below:
Contacts-->
John : 1334255
May : 3345777
James : 5799862
Ford : 4574878
How can I directly retrieve the contacts from the nodes with the key and value both as strings , without having to cast them into some object(that's not the string object).
I want to be able to display the names(keys) as contact names and the numbers(their values) as Contact number.

Please try this code:
DatabaseReference contactsRef = FirebaseDatabase.getInstance().getReference().child("Contacts");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String name = ds.getKey();
String contactNumber = ds.getValue(String.class);
Log.d("TAG", name + ": " + contactNumber);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
contactsRef.addListenerForSingleValueEvent(eventListener);
Hope it helps.

tl;dr write them as something other than numbers
The values in your example are Long (integers). Assuming they're phone numbers, you'll probably want to store them as strings anyway. When you write a value to Firebase, it will infer the type and store it as one of the following:
String (will appear in quotes)
Long (whole number)
Double (decimal number)
Boolean (true or false without quotes)
Map<String, Object> (key with children)
List<Object> (key with children)
In your case, since you want to treat it as a String type when it's being read, just write it as a string:
If you're setting the values from client code, use the String type when you create the value.
If you're manually entering them from the dashboard, you can either wrap them in quotes or use non-numeric characters like the familiar format (123) 456-7890. Any value you type in that doesn't evaluate to a Long/Double/Boolean will be interpreted as a String.

Firebase database Android - check if nickname exists if not create another one until we get a new nickname

I want to create a nickname to each user who login to my app for the first time. The nickname is the user's firstname and I add a number to it from 1 to 9 000 000. For example kevin Bond could get the nickname kevin123456.
I have all the nicknames stored in a node of my firebase database. Two users shouldn't have the same nickname, so I have to check wether the nickname already exists or not in my database. If it already exists, I want to create another nickname until I get a new nickname.
I currently:
- add a listener to the usernickname node
- in onDataChange I have a for loop to create a nickname, then I check if it already exists with dataSnapshot.hasChild(newNickname). If the nickname doesn't exist I do what I want with the nickname and break the for loop, if it exists I loop the for loop to try another nickname. Here is my code:
mFirebaseDatabase.getReference().child("usernickname").orderByKey().addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (int i = 0; i < 9000000; i++) {
final Random random = new Random();
randomNumberId = random.nextInt(9000000);
String newNicknameId = mFirstnameId + String.valueOf(randomNumberId);
//if the nickname already exists we restart the for loop to get a new random number
if (dataSnapshot.hasChild(newNicknameId)) {
i++;
//else if the nickname doesn't exists we create it and stop the loop
} else if (!dataSnapshot.hasChild(newNicknameId)) {
//do what I want...
break;
}
}
}
});
My issue is that I currently have to download all the nicknames node or at least all the nicknames beginning with the user's firstname. It is an issue for me because it could cost me a lot in GB downloaded if I have a lot of users :D
I guess I could use datasnapshot.exists() to check if the nickname exists without having to download all the nicknames, but I don't see how to create another nickname if it already exists. I cannot have a for loop outside of the listener and break it inside of the listener when needed.
Do you see what is the best way to create a new nickname for my users?
Thank you,
Alex

A better approach for unique nicknames would be to append a time stamp to the name:
username + new Date().getTime();
This will add a unique long like 1493808526335 and you can be certain that two users are unlikely to register in the same millisecond with the same name.

You need to use another aproch to check if a user exists. You need to change this line:
dataSnapshot.hasChild(newNicknameId);
with
dataSnapshot.child("userName").getValue().equals(newNicknameId);
In which userName is the name of field in which you store the newNicknameId, assuming your key -> value pair looks like this: userName: "newNicknameId"
Hope it helps.

final Query query = mFirebaseDatabase.getReference().orderByChild("usernickname").equalTo("yourNewNickName");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
//here means the value exist
//do whatever you want to do
} else {
//here means the value not exist
//do whatever you want to do
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});
use this will solve your problem. :)