Detect unpremium user

[mehmetpeker]

How can I detect if a user has not buy any product or subscription purchases?The functions 'onSubscriptionRestored' or 'onProductRestored' are not triggered if the user has not buy any purchase.Please add this callback to the library in future versions.

[jdleung]

It might a wrong way, but that's a solution I can find:

1. Set addBillingClientConnectionListener to check billing connection when app starts.
2. If status is true in onConnected, set all subscription and nonconsume products to false.
3. Then onSubscriptionRestored will be called if product is valid, just set the product to true again.

Important: be sure that the connection status is true before setting a product to false