从 Firebase 子项中检索整数

Question

I am trying to implement a counter for deals in my app. i am trying to recall the last integer written to the child eg deal number 10. i can successfully write a manually inputted value into firebase however i cannot retrieve the initial value.

i am using the following

dealnumRef = FirebaseDatabase.getInstance().reference
val numberRef = dealnumRef.child("Total_deals").orderByChild("deal_number")


val dealnumEventListener = object : ValueEventListener {
    override fun onDataChange(dataSnapshot: DataSnapshot) {
        for (ds in dataSnapshot.children) {

            val deal_num =
                ds.child("deal_number_cars").getValue()
            d("current deal number",deal_num.toString())
            val new_deal_num = deal_num + 1

the issue i have is that currently deal_num is pulling through as Any? . If i insert String::class.java into getvalue() it will bring it back as a string. But I need to keep it as an Integer to compute new_deal_num because new_deal_num will need to be written to the database and increment the deal_number to 11 as an example.

how do i extract deal_num as an integer?

I have checked available answers, but those indicate to convert to string. This would not work in my example, because i need to increment the deal number and hence keep it as an integer.

Answer 1

You can get the correct type from Firebase by passing its class into getValue(..) .

So:

val deal_num = ds.child("deal_number_cars").getValue(Long.class)

If you're storing a number in deal_number_cars in the database, this will get that value as a long .

Answer 2

The Full correction to the above is as follows:

dealnumRef = FirebaseDatabase.getInstance().reference
val numberRef = dealnumRef.child("Total_deals").orderByChild("deal_number_cars")


val dealnumEventListener = object : ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
    for (ds in dataSnapshot.children) {

        val deal_num =
            ds.getValue(Long::class.java)!!
        d("current deal number",deal_num.toString())
        val new_deal_num = deal_num + 1

You also have to make sure that you data model class is set as Long. i originally had it set as Int which created a small problem but was easily resolved.