Android In-App billing library: doubts about unlocking logic

Question

I have succeeded integrating the class BillingClient, starting the connection etc. I can, in fact, make a test purchase of the product from the App (it shows the payment form, buys the product etc.) I implemented it as it is described in this link that explains how to integrate the Google Play Billing Library.

It works, the purchase is performed... but I am clueless about how to implement the unlocking logic! For the record, it is only one product, non-consumable:

private void handlePurchase(Purchase purchase) {
    AcknowledgePurchaseResponseListener acknowledgePurchaseResponseListener = new AcknowledgePurchaseResponseListener() {
        @Override
        public void onAcknowledgePurchaseResponse(@NonNull BillingResult billingResult) {
            // TODO Ok, now what???
            if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK) {
                // TODO Handle the success of the "acknowledge"
                //      Unlock things etc...
            }

        }
    };

    if (purchase.getPurchaseState() == Purchase.PurchaseState.PURCHASED) {
        if (!purchase.isAcknowledged()) {
            AcknowledgePurchaseParams acknowledgePurchaseParams =
                    AcknowledgePurchaseParams.newBuilder()
                            .setPurchaseToken(purchase.getPurchaseToken())
                            .build();
            billingClient.acknowledgePurchase(acknowledgePurchaseParams, acknowledgePurchaseResponseListener);
        }

        // TODO Unlock from here?
        is_premium_unlocked = true;
    }
}

I am not sure howto implement the unlock: but for keeping it simple, let's say that the variable is_premium_unlocked will do the job. Will this grant it to be true after closing and reopening the App? I don't think so... Even though this handlePurchase is triggered onPurchaseUpdated, when this event occurrs? Only in new purchase requests? Every time the BillingClient connection is successful? I wonder about all of these things...

So, summarizing: What does my business logic have to do about the "acknowledging"? I am aware that this is some kind of mechanism to prevent duplicated purchases by the same user and stuff like that... but what should my App do about it, beyond what the code samples suggest? But most importantly: how is the app supposed to know that the "unlock product" is already purchased while starting? Is this done by some of the callbacks implemented by documentation's code samples, or have I to implement it my own way? Is there a way of, looking at the ProductDetails to check if it is has been already purchased before, and proceed to execute unlocking logic right away? Is this up to my code, or up to Google Play Billing Service?

The point is, what I have already done following those docs, lets the app "trigger" the unlock just after the product is purchased (AKA is_premium_unlocked = true), but I don't know how is the billingClient supposed to check if the product was already purchased in future connections, or if billingClient is able to do so at all in the first place.

SebasSBM · Answer

Finally, it was in the docs (I didn't read them hard enough). It looks like it must be done this way, by adding an async checker. So, if I trigger queryPurchasesAsync every time the billingClient connects successfully, I can trigger the unlock from there after app starts:

billingClient.queryPurchasesAsync(
    QueryPurchasesParams.newBuilder()
      .setProductType(ProductType.INAPP)
      .build(),
        new PurchasesResponseListener() {
          public void onQueryPurchasesResponse(BillingResult billingResult, List purchases) {
              is_premium_unlocked = true;
          }
        }
);

Android In-App billing library: doubts about unlocking logic

1 Answers