How to know if a user has used a free trial with Google Play Billing Library?

I can't seem to find any relevant information in the Purchase object returned by Google. I know there is a "getFreeTrialPeriod()" method for SkuDetails, but that only returns the duration of the free trial, and not if the user used the free trial or not.

Any ideas? Thanks!

Solution

This is only possible if you use backend to process subscriptions. Then from your server you can make a request that will return you JSON with purchase information, where you can find paymentState field.

Possible values:

0 - Payment pending
1 - Payment received
2 - Free trial

You can use it if you want to determine if the trial is active now. To determine if a trial was active in the past, your server should receive Real-time developer notifications and store information about purchased subscriptions.

For example, when you receive SUBSCRIPTION_PURCHASED notification, you can make the same request as above, to retrieve information about purchase. In the JSON you'll get there will be priceAmountMicros field. It should be 0 for trial. So you can store that on your server and check for it later.