Android Firebase检查孩子中是否存在数据

Question

I am developing an App that allows for its Users to see a certain Company's Buses and trains in Realtime.

Currently the Driver of a bus or tram registers by selecting which Route/Line he is working on with email and password and that get placed in a specific node in Firebase. For example, if the Driver selects Red Line then his UID is placed in Users => Drivers => RedLine => bus.

Then when the Driver Logs in, he can toggle a "I am Working" switch, which emits its location to the Users.

But when that happens I want that userID(userUID) to be placed in the "driversAvailable" node under a Branch which is the Route that UID is listed under in Users => Drivers, but I am battling to Find Answers.

void saveGeoFire(){
    final String userId = FirebaseAuth.getInstance().getCurrentUser().getUid();

    final DatabaseReference ref = FirebaseDatabase.getInstance().getReference("driversAvailable").child("drivers");
    final DatabaseReference driversRouteRef = FirebaseDatabase.getInstance().getReference().child("Users").child("Drivers");

    ValueEventListener driversAvailableEventListener = new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            if(dataSnapshot.exists()) // in Users => Driverrs => RedLine for example
            {
                //Create new Branch in "driversAvailable" => Drivers => RedLine => userID
            }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
        }
    };
driversRouteRef.addListenerForSingleValueEvent(driversAvailableEventListener);
}

My current Firebase Database:

Answer 1

okay, so after alot of trial and error, I figured it out, and its not as complicated as I was fearing it to be.

void saveGeoFire(){
    final DatabaseReference yellowRef = FirebaseDatabase.getInstance().getReference().child("driversAvailable").child("drivers").child("YellowLine");
    final DatabaseReference redRef = FirebaseDatabase.getInstance().getReference().child("driversAvailable").child("drivers").child("RedLine");

    final String userId = FirebaseAuth.getInstance().getCurrentUser().getUid();

    final DatabaseReference driversRouteRef = FirebaseDatabase.getInstance().getReference().child("Users").child("Drivers").child("Redline").child("bus");
    final DatabaseReference driversRouteRedRef = FirebaseDatabase.getInstance().getReference().child("Users").child("Drivers");
    ValueEventListener redRefEventListenter = new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if(dataSnapshot.exists()) {

                    if(dataSnapshot.child("RedLine").child("bus").getValue().toString().contains(userId)){
                        Toast.makeText(DriverMapActivity.this, "RedLinesuccess", Toast.LENGTH_SHORT).show();
                        GeoFire geoFire = new GeoFire(redRef);
                        geoFire.setLocation(userId, new GeoLocation(mLastLocation.getLatitude(),mLastLocation.getLongitude()));
                    }
                    if(dataSnapshot.child("YellowLine").child("bus").getValue().toString().contains(userId)){
                        Toast.makeText(DriverMapActivity.this, "YellowLine success", Toast.LENGTH_SHORT).show();
                        GeoFire geoFire = new GeoFire(yellowRef);
                        geoFire.setLocation(userId, new GeoLocation(mLastLocation.getLatitude(),mLastLocation.getLongitude()));
                    }

                }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    };
    driversRouteRedRef.addListenerForSingleValueEvent(redRefEventListenter);
}

My current Database