How to implement Android in app purchase in kotlin?

Question

I want to implement Google Play's billing for my android app's in-app purchase, which is written in kotlin. I am following this tutorial.

Here is my code:

private lateinit var billingClient: BillingClient
    private lateinit var productsAdapter: ProductsAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setupBillingClient()
    }

    private fun setupBillingClient() {
        billingClient = BillingClient
            .newBuilder(this)
            .setListener(this)
            .build()

        billingClient.startConnection(object : BillingClientStateListener {
            override fun onBillingSetupFinished(@BillingClient.BillingResponse billingResponseCode: Int) {
                if (billingResponseCode == BillingClient.BillingResponse.OK) {
                    println("BILLING | startConnection | RESULT OK")
                } else {
                    println("BILLING | startConnection | RESULT: $billingResponseCode")
                }
            }

            override fun onBillingServiceDisconnected() {
                println("BILLING | onBillingServiceDisconnected | DISCONNECTED")
            }
        })
    }

    fun onLoadProductsClicked(view: View) {
        if (billingClient.isReady) {
            val params = SkuDetailsParams
                .newBuilder()
                .setSkusList(skuList)
                .setType(BillingClient.SkuType.INAPP)
                .build()
            billingClient.querySkuDetailsAsync(params) { responseCode, skuDetailsList ->
                if (responseCode == BillingClient.BillingResponse.OK) {
                    println("querySkuDetailsAsync, responseCode: $responseCode")
                    initProductAdapter(skuDetailsList)
                } else {
                    println("Can't querySkuDetailsAsync, responseCode: $responseCode")
                }
            }
        } else {
            println("Billing Client not ready")
        }
    }


    private fun initProductAdapter(skuDetailsList: List<SkuDetails>) {
        productsAdapter = ProductsAdapter(skuDetailsList) {
            val billingFlowParams = BillingFlowParams
                .newBuilder()
                .setSkuDetails(it)
                .build()
            billingClient.launchBillingFlow(this, billingFlowParams)
        }
        //products.adapter = productsAdapter

    }

    override fun onPurchasesUpdated(responseCode: Int, purchases: MutableList<Purchase>?) {
        println("onPurchasesUpdated: $responseCode")
        allowMultiplePurchases(purchases)
    }

    private fun allowMultiplePurchases(purchases: MutableList<Purchase>?) {
        val purchase = purchases?.first()
        if (purchase != null) {
            billingClient.consumeAsync(purchase.purchaseToken) { responseCode, purchaseToken ->
                if (responseCode == BillingClient.BillingResponse.OK && purchaseToken != null) {
                    println("AllowMultiplePurchases success, responseCode: $responseCode")
                } else {
                    println("Can't allowMultiplePurchases, responseCode: $responseCode")
                }
            }
        }
    }

    private fun clearHistory() {
        billingClient.queryPurchases(BillingClient.SkuType.INAPP).purchasesList
            .forEach {
                billingClient.consumeAsync(it.purchaseToken) { responseCode, purchaseToken ->
                    if (responseCode == BillingClient.BillingResponse.OK && purchaseToken != null) {
                        println("onPurchases Updated consumeAsync, purchases token removed: $purchaseToken")
                    } else {
                        println("onPurchases some troubles happened: $responseCode")
                    }
                }
            }
    }

    companion object {
        private val skuList = listOf("get_5_coins", "get_10_coins")
    }

I also added implementation 'com.android.billingclient:billing:1.2.2' in my build.gradle and also added com.android.vending.BILLING and Internet uses-permission in my menifest file.

When I'm running this code, it is showing that billing client isn't ready.

Answer 1

1. Normally billing client doesn't work in emulator. So, either made the emulator work or easier way is to check it in real android phone, where the app will be downloaded using testers email.
2. Complete the google play set up very carefully. That part is very useful. The documentation I used over there is actually very good. I could not understood it fully first. It was my fault. Also, You can check this documentation.