Develop Reference

I don't want the data registration in Firebase to be numbered Android

I do not want numbering to appear, I want the time to appear as written in the code, so what is the reason for such a problem to appear?
deviceModels.add(new DeviceModel(newDeviceName, newDeviceWat, newDeviceUse, currentDateAndTime));
FirebaseDatabase firebaseDatabase = FirebaseDatabase.getInstance();
DatabaseReference databaseReference = firebaseDatabase.getReference();
databaseReference.child("DeviceInfo").child(currentUser).child(currentDateAndTime).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
// data base reference will sends data to firebase.
databaseReference.setValue(deviceModels);
Toast.makeText(MainActivity.this, "تم أضافة الجهاز", Toast.LENGTH_SHORT).show();
dialog.dismiss();
finish();
startActivity(getIntent());
}

It looks like your deviceModels is an array or a List, and this is how the Firebase Realtime Database persists arrays/lists. There is no way to configure it to do it differently, but you can of course use a different data type in your code.
More idiomatic in Firebase is to use the push() method when adding items to a list on the database. To learn more about why that is, have a look at Best Practices: Arrays in Firebase.
In your case you'd write the data for each individual DeviceModel:
databaseReference.push().setValue(new DeviceModel(newDeviceName, newDeviceWat, newDeviceUse, currentDateAndTime));
This will then end up in the database as:
DeviceInfo: {
"IN0r....T2": {
"-N.....": {
deviceId: ...,
deviceName: ...
}
}
}
And that entire list would then map back to a Map<String, DeviceModel> in your Java code.

Value return null when search a value using query firebase android studio

I want to ask, so I want to search a value which are an ID barcode on firebase. I try search on stackoverflow which using this line code.
tindakan = FirebaseDatabase.getInstance().getReference("tindakan");
bedahMulut = tindakan.child("Bedah Mulut");
Query searchByID = tindakan.orderByChild("ID").equalTo(idBarcode);
searchByID.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot idSnapshot : dataSnapshot.getChildren()) {
Log.v("hasil", "Found! -> " + idSnapshot.child("ID").getValue(String.class));
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.v("hasil", databaseError.toException().toString());
}
});
but this code are return null value, I already post structure firebase and debug session in below. Please help me in advance, thank you :)

It looks like you're trying to query a deeply nested data structure, which is not possible. Firebase Realtime Database queries operate on a flat list, where the property/value you order/filter on is at a fixed path under each direct child node.
The solution is typically to create an additional data structure, where you keep a simple list of IDs and then the value is the path of the node that has that ID.
"IDs": {
"INLAY": "/tindakan/Konservasi/Inlay/Kelas -"
}
See
Firebase Query Double Nested
Correct JSON structure to filter through data
Firebase Query all users with nested childs , with conditions (Nodejs)
Firebase query orderByChild
How does .indexOn works with users and unique keys?

Firebase and recyclerView

Hi I'm new in firebase and android studio and I have a problem
I want to store the data of this database in an array and next use the array to make a recycler view
Then in the main activity I wrote this:
And if I run the app only this is shown:
But if I do the same but instead of firebase i use a String[] with the data i want to show it works but i don't know why with firebase i can't.
if I change the references by this:
reference = database.getReference(FirebaseReferences.POKEMONS_REFERENCES);
reference.child(FirebaseReferences.APP_REFERENCES).addValueEventListener(new ValueEventListener() {
when I run the app, it automatically closes and i don't know what to do.
Could you please tell me what i'm doing wrong?
Thank you in advance.
Here is the logCat
https://github.com/adcasna/SearchViewPrueba2/wiki

Fisrts of all, please note that the Firebase documentation recommends against using arrays. Using an array is an anti-pattern when it comes to Firebase. One of the many reasons Firebase recommends against using arrays is that it makes the security rules impossible to write. If you still want to use this kind of structure, for getting those names and store them in an ArrayList, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference appRef = rootRef.child("pokemons").child("app");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> list = new ArrayList<>();
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String c_name = ds.child("c_name").getValue(String.class);
list.add(c_name);
Log.d("TAG", c_name);
}
Log.d("TAG", list );
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
appRef.addListenerForSingleValueEvent(eventListener);

How to search for a values of Child in firebase Android

DatabaseReference databaseReference=mDatabase;
String queryText="Hotel";
databaseReference.orderByChild("Coupon")
.startAt(queryText)
.endAt(queryText+"\uf8ff");
Here I attached the code which I used to get child names of "Coupon" when I entered the "Hotel" query under the Coupon.But I got blank.I supposed to get Hotel1,Hotel2 object.I'm new to firebase.So hope your support .Thanks in advance.

In the Web version, they use something called ElasticSearch, you could try to read more here: https://firebase.googleblog.com/2014/01/queries-part-2-advanced-searches-with.html
But for Android, I think there isn't any functionality to perform a search like that. What I would do is to query all the records then filter them myself:
DatabaseReference databaseReference = mDatabase;
mDatabase.addValueEventListener(new ValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot val : dataSnapshot.getChildren()){
//I am not sure what record are you specifically looking for
//This is if you are getting the Key which is the record ID for your Coupon Object
if(val.getKey().contains("Hotel")){
//Do what you want with the record
}
//This is if your are querying for the hotel child
if(val.child("hotel").getValue(String.class).contains("Hotel")){
//Do what you want with the record
}
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
}

Don't load your whole database to filter out needed data. It produces unnecessary traffic which has to be loaded, calculated and deleted. Instead, use:
DatabaseReference myRef = FirebaseDatabase.getDatabaseReference();
Query searchQuery = myRef.child("Coupon").orderByChild("hotel").equalTo("yourSearchString");
To make this code work, you also have to add indexOn on your corresponding attribute in the rules (of Firebase Database console).

FireBase Android Need 1 value saved under a single user

I have the following data structure on firebase for the user MF0qeRA4p7djfjgXxqwFOck3m6p02. I want to get the value of item3 to populate a single field into the User interface on an Android App. I have been looking through samples on Stackoverflow, but all I have found are outdated and do not work with the current version of firebase. I'm new to firebase completely and this is my first app on android. I've got the oncreate user method to populate the users email address and add the 4 item fields, but retrieving the data I'm completely lost and I am not sure where to even begin.
-Users
---MF0qeRA4p7djfjgXxqwFOck3m6p02
------item1:"1"
------item2:"2"
------item3:"3"
------item4:"4"

According to what I can identify is, you are facing problem retrieving data from this reference. Here is the code:
final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Users");
databaseReference.child("MF0qeRA4p7djfjgXxqwFOck3m6p02").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Map<String, Object> map=(Map<String, Object>)dataSnapshot.getValue();
String item3=(String)map.get("item3");
display(item3);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Hope this helps.

You can create a custom model and inside you can insert elements. Something like this:
public class Item {
private List<Object> ojects;
}
There you can save instance of Item on database. In this case you have more controll. Other case is to use push() method, that will generate a new encoded key, something like this:
mDatabase.child("items").push().put(new Object());