Android In-App-Purchase, how to check if user have purchased one item

Question

is that OK and safe to set a value in SharedPreference to flag that the user have purchased this item? What if user hack this value in SharedPreference. Or I need to connect IAP

Answer 1

As what Kuffs has mentioned, it is best to query the app-side implementation of the In-App Billing library which in turn queries the device's Google Play client. This will ensure that the purchase history most recently obtained from the Google Play servers would be reliable and relatively fresh information.

Also, keep in mind that if you are distributing the app on Google Play you MUST use the Google Play payment mechanism via In-App Billing. As it stands, Google Play and Wallet do NOT yet support Paypal or wire/bank transfer methods so you should not integrate the option if you are releasing it on Play.

http://play.google.com/about/developer-content-policy.html#payments