How to fetch nested data from Firebase to recycler view

Question

I am developing a simple database application, what I want is to print all the children (names) in one Recycler view, but I don't know how to implement the Kotlin code for that

FOLLOWING IS THE FORMAT OF THE JASON TREE

{
  "Head": {
    "Jack": {
      "Children_Info": {
        "Mike": {
          "age": "14",
          "name": "Mike"
        },
        "Tike": {
          "age": "16",
          "name": "Tike"
        }
      },
      "Spouse": {
        "name": "Fairy",
        "phone_No": "5543"
      },
      "name": "Jack",
      "phone_No": "4321"
    },
    "Max": {
      "Children_Info": {
        "Bill": {
          "age": "12",
          "name": "Bill"
        },
        "Jill": {
          "age": "14",
          "name": "Jill"
        }
      },
      "Spouse": {
        "name": "marry",
        "phone_No": "3346"
      },
      "name": "Max",
      "phone_No": "1234"
    }
  }
}

My code for DATACLASS

data class data_View(val name : String? = null,
val age : String? = null)

CODE FOR FETCHING DATA

dbref = FirebaseDatabase.getInstance().getReference("Head")**.child("Jack")**.child("Children_Info")

dbref.addValueEventListener(object : ValueEventListener{
    override fun onDataChange(snapshot: DataSnapshot) {

        if(snapshot.exists()){
            for (usersnapshot in snapshot.children){

                val user = usersnapshot.getValue(data_View::class.java)
                userArrayList.add(user!!)

            }
            var adapter = AdapterClass(this@MainActivity,userArrayList)
            recyclerView.adapter = adapter
            adapter.setOnItemClickListener(object : AdapterClass.onItemClickListener{
                override fun onItemClick(position: Int) {
                    Toast.makeText(applicationContext, "YOU CLICKED ON $position", Toast.LENGTH_SHORT).show()

                }    
            })
        }
    }

In the first line I typed the parent name .child("Jack") to get children printed in recycler view, but how do I loop through all the parents at once.

THIS IS WHAT I GOT

But according to my database I need all children to be displayed in my recyclerview ie, mike,tike,bill,jill

Answer 1

It sounds like you want to retrieve the entire Head node and then loop over the various levels of child nodes in your onDataChange method:

dbref = FirebaseDatabase.getInstance().getReference("Head")

dbref.addValueEventListener(object : ValueEventListener{
    override fun onDataChange(snapshot: DataSnapshot) {
        for (parentSnapshot in snapshot.children) {
            // parentSnapshot is Jack or Max, so we'll loop over its Children_Info
            for (usersnapshot in parentSnapshot.child("Children_Info").children){
                val user = usersnapshot.getValue(data_View::class.java)
                userArrayList.add(user!!)
            }
        }
        ...
    }