如何从Firebase中检索数据列表并将其存储到ArrayList<>

我有一个Firebase数据库，我想从那里检索数据列表并存储到ArrayList中。

产品模型很好，可以正常工作。

class Product(var pName: String?,var pUnit: Int,var pPrice: Double,var pAmount: Double)


但是以某种方式我无法从数据库中获取“项目”列表。
我想要的是获取pname，punit，pprice和pamount并将其存储在ArrayList

我对数据库的引用是这个

ref = FirebaseDatabase.getInstance().getReference().child("Sales")
ref.addValueEventListener(object : ValueEventListener{
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(p0: Datasnapshot) {
var sira: Int = 0
ref.addListenerForSingleValueEvent(object : ValueEventListener {
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(p1: Datasnapshot) {
println("onDataChange")
if (p0.exists()) {
list.clear()
for (h in p0.children) {
val dateR = h.child("date").value.toString()
val discountR = h.child("discount").value.toString()
val dueR = h.child("due").value.toString()
val nameR = h.child("name").value.toString()
val totalR = h.child("total").value.toString()
val subtotalR = h.child("subTotal").value.toString()
val timeR = h.child("time").value.toString()
val name = h.child("pname").value.toString()
val unit = h.child("punit").value.toString()
val price = h.child("pprice").value.toString()
val amount = h.child("pamount").value.toString()
productList.add(Product(name,unit.toInt(),price.toDouble(),amount.toDouble()))


这是json文件

{
"-Lw37--uyfuBA0AfTalp" : {
"date" : "14/12/2019","discount" : 0.24,"due" : 0,"items" : [ {
"pamount" : 2.4,"pname" : "Granola","pprice" : 2.4,"punit" : 1
} ],"paym" : [ {
"paymentAmnt" : 0.02,"paymentDesc" : "Cash Payment :"
},{
"paymentAmnt" : 2.14,"paymentDesc" : "Card Payment :"
} ],"subTotal" : 2.4,"time" : "11:16:42","total" : 2.16
},"-Lw5Qx8sVdw3ZCMiXAL-" : {
"date" : "14/12/2019","discount" : 1,"items" : [ {
"pamount" : 4.8,"punit" : 2
},{
"pamount" : 2.6,"pname" : "Brownie","pprice" : 2.6,"punit" : 1
},"punit" : 1
} ],"name" : "James Brown","paym" : [ {
"paymentAmnt" : 3,"paymentDesc" : "Cash Payment :"
},{
"paymentAmnt" : 5,"paymentDesc" : "Staff Markout :"
},{
"paymentAmnt" : 1,"subTotal" : 10,"time" : "22:03:07","total" : 9
},"-Lw5T4TfYUTXsWKAndBx" : {
"date" : "14/12/2019","due" : -0.84,"paymentDesc" : "Cash Payment :"
} ],"time" : "22:12:26","-Lw5UWguHS18IwWE6elT" : {
"date" : "14/12/2019","discount" : 0.26,"due" : -1.66,"items" : [ {
"pamount" : 2.6,"paym" : [ {
"paymentAmnt" : 4,"subTotal" : 2.6,"time" : "22:18:43","total" : 2.34
},"-Lw5ypp5xJLJO53bjejk" : {
"date" : "15/12/2019","discount" : 0,"due" : -1.6,"paymentDesc" : "Cash Payment :"
} ],"time" : "00:35:32","total" : 2.4
},"-LwANPC0UYCmTnqm7DRV" : {
"date" : "15/12/2019","punit" : 1
},{
"pamount" : 2.4,"paym" : [ {
"paymentAmnt" : 5,{
"paymentAmnt" : 4,"time" : "21:05:43","total" : 9
}
}


但是，请帮助我在这里做错了什么。任何帮助表示赞赏。

谢谢。

您可以尝试：使用GenericTypeIndicator获取列表数据。

您可以引用我的github：https://github.com/vancuong0429/stack_59350042

private lateinit var database: DatabaseReference
private var productList: ArrayList = arrayListOf()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
database = FirebaseDatabase.getInstance().getReference("Sales")
database.addValueEventListener(object: ValueEventListener {
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(p0: DataSnapshot) {
productList.clear()
for (snapshot in p0.children) {
if (snapshot.hasChild("items")) {
val generic: GenericTypeIndicator> =
object : GenericTypeIndicator>() {}
val items = snapshot.child("items").getValue(generic)
items?.let { productList.addAll(it) }
}
}
}
})
}
class Product {
var pName: String? = null
var pUnit: Int? = null
var pPrice: Double? = null
var pAmount: Double? = null
}