Android in-app purchase of a subscription with a free trial - how to avoid abuse?

Question

I've searched high and low for guidance on how best to address this... I've read Google Play In-App Subscriptions (http://developer.android.com/google/play/billing/billing_subscriptions.html) and the section on Implementing Subscriptions (http://developer.android.com/google/play/billing/billing_integrate.html#Subs) but I still don't see a way to avoid abuse.

I've also seen the related question here - Google Inapp purchasing and trial period. However, using the SharedPreferences is subject to relatively easy abuse.

I have an app that will require a subscription for full functionality. I set up a monthly subscription in-app purchase product, say ID = "myapp.subscription.monthly", costing $0.99/month. I want to give people a chance to experience the full functionality, so I give "myapp.subscription.monthly" a 30-day trial period.

When the user installs the app for the first time, they are prompted to purchase the monthly subscription, they are charged $0.00 and told that starting 30 days from now their card will start getting charged $0.99/month.

When my app calls "getPurchases()", the fact that they have a subscription will be returned.

If they cancel during the free trial, or say after a couple of months of billing, a call to "getPurchases()" returns nothing, according to the "Implementing" section:

The call returns a Bundle with all the active subscriptions owned by the user. Once a subscription expires without renewal, it will no longer appear in the returned Bundle.

Since the user has no active subscriptions, my app will prompt them to purchase the subscription for full functionality. Again, they will get the 30-day free trial.

I've thought about having a second subscription product, say "myapp.subscription.monthly.no.free.trial" and I would have that be the available item for purchase. However, without a way to ask Google Play if the user ever previously purchased a subscription, my app can't know that is should be offering the "no free trial" product.

So, how to avoid someone just subscribing and cancelling over and over to keep getting the free 30 days? Is there a way to ask Google Play for the complete purchase history?

Answer 1

According to documentation (https://support.google.com/googleplay/answer/2476088?hl=en, Trial subscriptions), its says:

You can't sign up for multiple trials.

I guess Google automatically handle this