Android : Android in-app purchasing: free credit vs. free trial

Android's in-app billing supports subscriptions with a free trial period:

... users [can] try your subscription content before buying it. The trial period runs for the period of time that you set and then automatically converts to a full subscription ...

This is attractive, but such a model is

• open to abuse (e.g., a free magazine trial would allow a user to download all content)

and, moreover,

• forces user commitment (i.e., users commit to a subscription, albeit, can make the effort to cancel).

Using the magazine example as an analogy, I'd rather

1. allow the user to download 10 articles for free, and then


2. offer the user the opportunity to subscribe.

Intuitively, (1) can be modelled by giving the user 10 items of credit and consuming an item of credit for every download. Once the free credit has been exhausted, (2) can be captured by offering the user a subscription. Unfortunately, I cannot see how the billing API can support this. Any suggestions?

An insecure solution

One solution would be for the app to allow 10 downloads before offering a subscription, but the subscription mechanism can be circumvented by clearing the app's data.