Firebase Database multiple strings in one child - firebase

Question

im working with firebase for a couple months and so far i had no issues until now. im using kotlin and my problem is simple but i cant find a way out. i storage strings in database: path"/user/friends" , but i cant change the variable name and the strings were overwriting itselves. My solution was use "push()" until the "setValue()", but with this i have the following firebase structure:
"users": {
"yvrYpjMwVSPBvMAvDGo26hPlWWQ2": {
"email": "vinibarros.sp#gmail.com",
"friends": {
"-LfD9z6ke7FXFjxUb4td": {
"email": "teste#gmail.com"
},
"-LfDA-NaAYAMoWiPhXy4": {
"email": "teste2#gmail.com"
}
},
"primeiroLogin": true,
"stars": 0,
"tutorialComplete": false,
"uid": "yvrYpjMwVSPBvMAvDGo26hPlWWQ2",
"username": "Vinicius Barros"
}
}
basically hashmaps inside a hashmap ps:lol mindblow
how do i get the pushcode.value into an arraylist?
i have a class user that have the friend variable, until now this variable was typed as hashMap. and the call to get the email was "user.friends.value"
this worked because was one friend....
com.google.firebase.database.DatabaseException: Failed to convert value of type java.util.HashMap to String
When I added more than one user I got this error that references my class user, where have a "hashMap". But the firebase gives me another hashmap instead of string. I was thinking about: hashMap<hashMap<String,String>, null>.
i 've tried this:
class friends:
#Parcelize
class Friend(val hashMap: HashMap < String, String > ? ): Parcelable {
constructor(): this(null)
}
The activity where i show the friends:
val ref2 = FirebaseDatabase.getInstance().getReference("/users/" + cUid + "/friends/")
ref2.addListenerForSingleValueEvent(object: ValueEventListener {
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(p0: DataSnapshot) {
p0.children.forEach {
val friend = it.getValue(Friend::class.java)
Log.d("teste", it.toString())
if (friend != null) {
Log.d("teste", friend.hashMap ? .values.toString())
//friends.add(friend.hashMap?.values.toString())
}
}
}
})
this keeps returning null....

Answer 1

With your Friend class, the Firebase client looks for a JSON for each friend with this structure:
"-LfD9z6ke7FXFjxUb4td": {
"hashMap": {
...
}
},
This is because you're defining your Friend class with a property hashMap like this: class Friend(val hashMap: HashMap < String, String > ? ).
To be able to read your current structure, you'll need to define a data class like this:
data class Friend (
val email: String? = null
}
Now the email in the Friend class matched the email property in the JSON. And since email has a default value, the Friend class will have a default no-argument constructor, which Firebase relies on.

Answer 2

Solved!
After get into /friends
i did this:
var friends : ArrayList<String> = arrayListOf()
the onDataChanged where i get the string friend
override fun onDataChange(p1: DataSnapshot) {
p1.children.forEach { it1 ->
val friend = it1.value as String
friends.add(friend)
}
}