如何从 kotlin 上的 firebase 数据库中获取键和值

Question

I'm new to android development and im having a bit of problem with firebase database. I'm creating a app somewhat similar to e-commerce application.

category1
    child1
         name: nameOfChild1
         value: value
    child2
         name: nameOfChild2
         value: value
    child3

This is how my database is structured. im using

dbref = FirebaseDatabase.getInstance().getReference("requiredCategory")
        dbref.addValueEventListener(object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                if (snapshot.exists()) {
                    for (productSnapshot in snapshot.children) {
                        val product = productSnapshot.getValue(Product::class.java)
                        productlist.add(product!!)
                    }
                    productrecyclerview.adapter = productAdapter(productlist)
                }
            }

And Product class is

data class Product(
    var id: String? = null,
    var price: String? = null,
)

Instead i would like to change my structure to

category1
    child1
      nameOfNested1: value
      nameOfNested2: value
    child2
      nameOfNested1: value
      nameOfNested2: value
    child3
      nameOfNested1: Value
      nameOfNested2: value

category2
    child1
    child2
    child3

I want to retrive both the key: nameOfNested and value:value .How do i go on and change the code get both the id and value? Thanks in Advance

Answer 1

If you also want to get the key of each product, you can do so with:

for (productSnapshot in snapshot.children) {
    val key = productSnapshot.key // 👈
    val product = productSnapshot.getValue(Product::class.java)
    ...

Answer 2

Let me answer with what i got working and also be a bit more specific about what i was trying to accomplish

First of all, let me start with what i was doing. i had a Firebase Realtime Database that looked like this (Only an example for demonstration purpose)

Students
   Riya
     name: Riya 
     class: 10
   Benson
     name: Benson
     class: 9
   Merlin
     name: Merlin
     class: 7

I Made a student class that looks like this

data class Student(
    var name: String? = null,
    var class: String? = null,
)

I found a snippet online that would retrieve data from db that is given below

dbref = FirebaseDatabase.getInstance().getReference("Students")
        dbref.addValueEventListener(object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                if (snapshot.exists()) {
                    for (studentSnapshot in snapshot.children) {
                        val student = studentSnapshot.getValue(Student::class.java)
                       studentlist.add(student!!)
                    }
                    myrecyclerview.adapter = thisAdapter(studentlist)
                }
            }

It gave a Array that look something like this

[Student(name=Riya, class=10), Student(name=Benson, class=9), Student(name=Merlin, class=7)]

As you can see, the structure that i was using was inefficient and i want to change it. Also, instead of a single Students refence i wanted to add child which holds the students based on the class they are in. Also i wanted to add age property to each student as well. So i came up with a structure that looks like this

Students
   Class7
      Joe: 12
      Mary: 11
      Ann: 12
   Class8
      Michael: 12
      Lucy: 12
   Class9
      Ricko: 15
      Anna: 14

Staff
    class7
      Janet:25
      Bob: 34

What i was having issue with getting Both the Key and value at the same time. what at the time i was using was

FirebaseDatabase.getInstance()
            .getReference("Students")
            .child(requiredClass)
            .addValueEventListener(object : ValueEventListener {
                override fun onDataChange(snapshot: DataSnapshot) {
                    if (snapshot.exists()) {
                        for (studentSnapshot in snapshot.children) {
                     val student = studentSnapshot.getValue(Student::class.java)
                            studentlist.add(student!!)
                        }

It was not working with what i had.. It was looking for ids name and age . (i renamed the class to age in the Student class)

I got it working by doing something like this

FirebaseDatabase.getInstance()
            .getReference("Students")
            .child(requiredClass)
            .addValueEventListener(object : ValueEventListener {
                override fun onDataChange(snapshot: DataSnapshot) {
                    if (snapshot.exists()) {
                        for (studentSnapshot in snapshot.children) {

                            val student = Student()
                            student.name = studentSnapshot.key.toString()
                            student.age = studentSnapshot.value.toString()
                            studentlist.add(student!!)
                        }

This works fine and returns a array that i wanted.

I know most of that explanation was unnecessary. i wanted to clarify what my situation was. Also my solution might be the worst. If anyone have a better solution, i'm all ears...