图3和代码A是来自play-billing-samples项目，可以看到here。
从文档中可以看出，当用户想要购买东西时，可以通过点击按钮来触发launchBillingFlow，然后onPurchasesUpdated就会启动。
我对override fun onBillingSetupFinished(billingResult: BillingResult){ }的评论感到困惑，onBillingSetupFinished（包括processPurchases()）将在BillingClient成功建立后启动。
通常情况下，我需要首先初始化BillingClient，onBillingSetupFinished被启动，processPurchases()也会被启动，然后我点击一个 Buy 按钮，onPurchasesUpdated将被启动，processPurchases()将再次启动。
代码有问题吗？

* Figure 3 -- Server-reliant billing integration with offline access to some entitlements
 *
 *  _____                        _________________
 * |Start|----------------------|launchBillingFlow|
 *  -----                        -----------------
 *                                        |
 *                                  ______v____________
 *                                 |onPurchasesUpdated |
 *                                  -------------------
 *                                 /      |
 *                   ITEM_ALREADY_OWNED   |
 *                               /        |
 *  _____       ________________v__       |
 * |Start|-----|queryPurchasesAsync|      OK
 *  -----       -------------------       |
 *                               \        |
 *                               v________v_______
 *                              |processPurchases |
 *                               -----------------
 *                                        |
 *   

                                 |

代码A

/**
     * This is the callback for when the connection to the Play [BillingClient] has been successfully
     * established. It might make sense to get [SkuDetails] and [Purchases][Purchase] at this point.
     */
    override fun onBillingSetupFinished(billingResult: BillingResult) {
        when (billingResult.responseCode) {
            BillingClient.BillingResponseCode.OK -> {
                Log.d(LOG_TAG, "onBillingSetupFinished successfully")
                querySkuDetailsAsync(BillingClient.SkuType.INAPP, GameSku.INAPP_SKUS)
                querySkuDetailsAsync(BillingClient.SkuType.SUBS, GameSku.SUBS_SKUS)
                queryPurchasesAsync()
            }
            BillingClient.BillingResponseCode.BILLING_UNAVAILABLE -> {
                //Some apps may choose to make decisions based on this knowledge.
                Log.d(LOG_TAG, billingResult.debugMessage)
            }
            else -> {
                //do nothing. Someone else will connect it through retry policy.
                //May choose to send to server though
                Log.d(LOG_TAG, billingResult.debugMessage)
            }
        }
    }


    override fun onPurchasesUpdated(
            billingResult: BillingResult,
            purchases: MutableList<Purchase>?
    ) {
        when (billingResult.responseCode) {
            BillingClient.BillingResponseCode.OK -> {
                // will handle server verification, consumables, and updating the local cache
                purchases?.apply { processPurchases(this.toSet()) }
            }
            BillingClient.BillingResponseCode.ITEM_ALREADY_OWNED -> {
                // item already owned? call queryPurchasesAsync to verify and process all such items
                Log.d(LOG_TAG, billingResult.debugMessage)
                queryPurchasesAsync()
            }
            BillingClient.BillingResponseCode.SERVICE_DISCONNECTED -> {
                connectToPlayBillingService()
            }
            else -> {
                Log.i(LOG_TAG, billingResult.debugMessage)
            }
        }
    }

   fun queryPurchasesAsync() {
       ...
       processPurchases(purchasesResult)
   }