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Retrieve count data from Firebase Java

I am trying to count the number of children in my DB table that meet a certain condition. If the isSeen column equals false then I want to count that, if it equals true I don't want to count it.
Currently, it's not working but if I change the query from Query query = usersRef.orderByChild("isSeen").equalTo(true); to Query query = usersRef.orderByChild("isSeen"); I get a number but it's not the correct way. Can someone please help me?
Rules:
{
"rules": {
".read": true,
".write": true,
"Messages": {
".indexOn": "isSeen"
}
}
}
"Messages": {
"b3vYlKZFrje0e3wHyBlWIK4ooK93": {
"DIt5bGqw2WS4eGHNqQJKxZSn3B72": {
"-N8NCgnwX6V7ghfGlcWS": {
"dateAdded": 1659337356887,
"date_time": "Aug-01-2022 3:02:36 AM",
"from": "DIt5bGqw2WS4eGHNqQJKxZSn3B72",
"isSeen": true,
"message": "Yoo",
"to": "b3vYlKZFrje0e3wHyBlWIK4ooK93",
"type": "text"
},
"-N99iQjlMfeyOM_VCAEB": {
"dateAdded": 1660184797462,
"date_time": "Aug-10-2022 10:26:37 PM",
"from": "DIt5bGqw2WS4eGHNqQJKxZSn3B72",
"isSeen": true,
"message": "Wassup",
"to": "b3vYlKZFrje0e3wHyBlWIK4ooK93",
"type": "text"
}
}
}
},
DatabaseReference usersRef = FirebaseDatabase.getInstance().getReference("Messages");
Query query = usersRef.child(firebaseUser.getUid()).orderByChild("isSeen").equalTo(true);
query.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
#Override
public void onComplete(#NonNull Task<DataSnapshot> task) {
if (task.isSuccessful()) {
long count = task.getResult().getChildrenCount();
Log.d("TAG1", "count: " + count);
} else {
Log.d("TAG2", task.getException().getMessage()); //Never ignore potential errors!
}
}
});
Error message:
D/TAG2: Index not defined, add ".indexOn": "isSeen", for path "/Messages/b3vYlKZFrje0e3wHyBlWIK4ooK93", to the rules
Database schema

When you're using the following query:
Query query = usersRef.orderByChild("isSeen").equalTo(true);
Firebase will always return the exact data you are querying, meaning that you'll get all elements that have the isSeen field set to true. Please note that there is no way you can query by a negation. So something like this is not possible:
Query query = usersRef.orderByChild("isSeen").notEqualTo(true);
// 👆
According to your comment in which you say that you don't have any elements where the isSeen field is set to true, then your query will yield no results, and that's the expected behavior.
While #TimothyPham's answer will work, using getChildrenCount() might be the best solution. Why? Because if you have a lot of messages this operation requires you to read all of them in order to provide a number. The best solution I can think of would be to increment/decrement a counter as explained in my answer from the following post:
How to save users score in firebase and retrieve it in real-time in Android studio
Edit:
Query query = usersRef.orderByChild("isSeen").equalTo(true);
query.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
#Override
public void onComplete(#NonNull Task<DataSnapshot> task) {
if (task.isSuccessful()) {
long count = task.getResult().getChildrenCount();
Log.d("TAG", "count: " + count);
} else {
Log.d("TAG", task.getException().getMessage()); //Never ignore potential errors!
}
}
});
But this code will only work if you have elements in the database that have he isSeen field is set to true.

I think you should try this, it working for me. It read your messages for the first time
usersRef.orderByChild("isSeen").equalTo(true).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
Log.d("TAG", "Count:" + String.valueOf(dataSnapshot.getChildrenCount()));
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

Try this:
Log.e(dataSnapshot.getKey(),dataSnapshot.getChildrenCount() + "");

why is it redirecting to the page which is suppose to happen in else clause even when the if statement is true(i feel)

So in my database, I have 2 nodes Customer and Driver. And I tried to make the login page in such a way that if the user is in the driver node he goes to the page meant for driver and the same way for the customer. My problem is even when it is Driver it is still going to the customer page.
#Override
public void onClick(View v) {
progressdialog.show();
auth.signInWithEmailAndPassword(binding.Email.getText().toString(),binding.Password.getText().toString())
.addOnCompleteListener(new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
progressdialog.dismiss();
if(task.isSuccessful()){
Toast.makeText(Login_Page.this, "Success", Toast.LENGTH_SHORT).show();
String uid = auth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference uidRef = rootRef.child("Driver");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
if(snapshot.exists()) {
Toast.makeText(Login_Page.this,"LoginDriver",Toast.LENGTH_SHORT);
Intent intent=new Intent(Login_Page.this, HomePage.class);
startActivity(intent);
}
else {
startActivity(new Intent(Login_Page.this, Custhomepage.class));
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
};
uidRef.addListenerForSingleValueEvent(valueEventListener);
}
In this code, When the child is Driver it is supposed to go to the home page but instead, it goes to custhomepage even when the node is in Driver.
This is the database values:
{
"Users" : {
"Customer" : {
"5JEgU9isvdWFop4yt0lGFt9iSEo1" : {
"mail" : "Ashh#bbyshark.com",
"password" : "AlexXalexa",
"username" : "Ashhh"
},
"VyxUiy60khMEr4LPsNiKRTIxRs72" : {
"mail" : "xxx#g.com",
"password" : "yvuuuuuu",
"username" : "xxx"
},
"aRmz8jnue1NeDeGA08ey9H4rvIJ3" : {
"mail" : "aa#gmail.co.cin",
"password" : "123344555",
"username" : "aa"
},
"kgG9GBSK6xVdQUdTKEAnuU3OROv1" : {
"mail" : "tttt#class.com",
"password" : "---------------",
"username" : "j need"
},
"pWnRecYxRlQMwUJH5bZ10My5cBi1" : {
"mail" : "Ashh#babyshark.com",
"password" : "AlexXalexa",
"username" : "Ashhh"
},
"qHctsriB2GZYzQ2NULw0PmBdCkV2" : {
"mail" : "arfan#gmail.com",
"password" : "123456yus",
"username" : "Arfan"
}
},
"Driver" : {
"ZMqeFvM4gTh2vjTVu31JQY2jz9x2" : {
"mail" : "aww#gmail.com",
"password" : "696969",
"username" : "aditya"
}
}
}
}

Looks like you're adding the ValueEventListener to the entire Driver node so it is seeing if a snapshot exists at "Users/Driver" which it does. Instead the ValueEventListener should be attached to the child node using the UID to check if a snapshot exists at "Users/Driver/{UID}".
Changing this line:
DatabaseReference uidRef = rootRef.child("Driver");
To this:
DatabaseReference uidRef = rootRef.child("Users").child("Driver").child(uid);
Should solve the issue.

Get index data with setIndexedQuery where index not end of path

I have a Firebase realtime database with a layout similare to this:
{
"data": {
"index_1": {
"xxx": {
"value_1": "Some data",
"value_2": true
},
"index_2": {
"xxx": {
"value_1": "Some data",
"value_2": true
},
"index_3": {
"xxx": {
"value_1": "Some data",
"value_2": true
},
},
"keys": {
"user1": {
"index_1": true,
"index_2": true
},
"user2": {
"index_1": true,
"index_3": true
}
}
}
And a simple java class:
public class Data {
private String value_1;
private Boolean value_2;
...
getters/setters
...
}
Is there any (easy) way to get objects from /data/{index}/xxx/{object}?
If the layout had been /data/{index}/{object}, eg:
"data": {
"index_1": {
"value_1": "Some data",
"value_2": true
}
}
it's is possible to use
keyQuery = FirebaseDatabase.getInstance()
.getReference("keys")
.orderByKey();
dataRef = FirebaseDatabase.getInstance().getReference("data");
FirebaseRecyclerOption<Data> options = new FirebaseRecyclerOptions.Builder<Data>().
.setIndexedQuery(keyQuery, dataRef, Data.class)
.build();
but I havn't found any way to do this when the index isn't just before the wanted data.

I found a way to solve it using FirebaseRecyclerOption by creating a custom SnapshotParser
SnapshotParser<Data> parser = new SnapshotParser<Data>() {
#NonNull
#Override
public Data parseSnapshot(#NonNull DataSnapshot snapshot) {
return snapshot.child("xxx").getValue(Data.class);
}
}
FirebaseRecyclerOption<Data> options = new FirebaseRecyclerOptions.Builder<Data>().
.setIndexedQuery(keyQuery, dataRef, parser)
.build();

Is there any (easy) way to get objects from /data/{index}/xxx/{object}?
Yes it is, using the following lines of code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference dataRef = rootRef.child("data");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String value_1 = ds.child("xxx").child("value_1").getValue(String.class);
boolean value_2 = ds.child("xxx").child("value_2").getValue(Boolean.class);
Log.d(TAG, value_1 + " / " + value_2);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
dataRef.addListenerForSingleValueEvent(valueEventListener);
If you want to use FirebaseRecyclerOption, you database schema should indeed looks like this:
"data": {
"index_1": {
"value_1": "Some data",
"value_2": true
}
}
Without that extra xxx child.

Make username unique with rules [duplicate]

Parse will shut down at the end of the year, so I decided to start using Firebase. I need to implement a register process with 3 fields : email, username, password (Email & username must be unique for my app).
Since, Firebase is not providing an easy way to manage username like Parse, I decided to use only the email/password registration and save some additional data like username. Here is my users data structure :
app : {
users: {
"some-user-uid": {
email: "test#test.com"
username: "myname"
}
}
}
But, what I want to do is to make the username unique and to check it before creating an account.
These are my rules :
{
"rules": {
".read": true,
".write": true,
"users": {
"$uid": {
".write": "auth !== null && auth.uid === $uid",
".read": "auth !== null && auth.provider === 'password'",
"username": {".validate": "!root.child('users').child(newData.child('username').val()).exists()"}
}
}
}
}
Thank you very much for your help

Part of the answer is to store an index of usernames, that you check against in your security rules:
app : {
users: {
"some-user-uid": {
email: "test#test.com"
username: "myname"
}
},
usernames: {
"myname": "some-user-uid"
}
}
So the usernames node maps a username to a uid. It essentially reads as "username 'myname' is owned by 'some-user-uid'".
With this data structure, your security rules can check if there is already an entry for a given username:
"users": {
"$uid": {
".write": "auth !== null && auth.uid === $uid",
".read": "auth !== null && auth.provider === 'password'",
"username": {
".validate": "
!root.child('usernames').child(newData.val()).exists() ||
root.child('usernames').child(newData.val()).val() == $uid"
}
}
}
This validates that the username isn't claimed by anyone yet OR it is claimed by the current user.

Save usernames as suggested by Frank but when you save usernames, use runTransaction function in Firebase to make sure that the username is not taken. This function is guaranteed by Firebase to be an atomic operation so you can be rest assured of no collision
firebaseRef.child("usernames").child(username).runTransaction(new Transaction.Handler() {
#Override
public Transaction.Result doTransaction(MutableData mutableData) {
if (mutableData.getValue() == null) {
mutableData.setValue(authData.getUid());
return Transaction.success(mutableData);
}
return Transaction.abort();
}
#Override
public void onComplete(FirebaseError firebaseError, boolean commited, DataSnapshot dataSnapshot) {
if (commited) {
// username saved
} else {
// username exists
}
}
});

make a new branch for username and when new user login get list of all username and check wether it is present in db or not if it is present show them toast otherwise put its username in the username branch ..

I dont know much about firebase security yet, but I may have solved the problem using Java. I have posted it below.
my data structure is
myapp
{
users: {
<unique generated-id>
{ username: "example.username" }
}
}
public boolean isUsernameExists(final String enteredUsername) {
final Boolean[] isExist = {false};
FBref.child("users").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot userSnapshot : dataSnapshot.getChildren()) {
String existingUsername = (String) userSnapshot.child("userName").getValue();
if (existingUsername.equals(enteredUsername)) {
isExist[0] = true;
}
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
//some error thrown here
}
});
return isExist[0];
}

Login using email stored in firebase realtime database

I am developing an android App in which I implemented Firebase realtime database. And now I want to login using by email id and password which stored in database. I know firebase auth can be use for authentication but I want to login using realtime database like we do in Sql or my sql.

I done this. First I fetch data of particular email id from database and than compare its password and assign the related function to do..
Query query = databaseReference.child("users").orderByChild("email").equalTo(txvUsername.getText().toString().trim());
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
// dataSnapshot is the "issue" node with all children with id 0
for (DataSnapshot user : dataSnapshot.getChildren()) {
// do something with the individual "issues"
UsersBean usersBean = user.getValue(UsersBean.class);
if (usersBean.password.equals(txvPassword.getText().toString().trim())) {
Intent intent = new Intent(context, MainActivity.class);
startActivity(intent);
} else {
Toast.makeText(context, "Password is wrong", Toast.LENGTH_LONG).show();
}
}
} else {
Toast.makeText(context, "User not found", Toast.LENGTH_LONG).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Thanks..

I am assuming that you know how to use ValueEventListener, onDataChange method and Datasnapshot.
As you stated above, you want to do it like in SQL or MySQL. So instead of using email, I will use username and password.
You can authenticate your user without using Firebase Authentication. However, this is not recommended for the database security.
{
"userList": {
"JRHTHaIsjNPLXOQivY": {
"userName": "userA",
"password": "abc123"
},
"JRHTHaKuIFIhnj02kE": {
"userName": "userB",
"password": "abc123"
}
},
"userAuth": {
"userA": "JRHTHaIsjNPLXOQivY",
"userB": "JRHTHaKuIFIhnj02kE"
}
}
As you can see above I have saved the the userName and userId in firebase db. When a user enter the username and password, you should read the userId by using username in the userAuth. Once you have retrieved the userID, use it to access the userList for the user details. This is where you check for the entered password.
{
"userList": {
"userA": {
"password": "abc123"
},
"userB": {
"password": "abc123"
}
}
}
Or you can just authenticate your users like this.