How to work with In-App Billing (Android Development)?

Question

Google

Hello. I re-read a bunch of information on the Internet, but did not figure out how to use Android In-App Billing in my application. I created content for sale in the developer panel, connected the necessary classes from the SDK and the library, what should I do next? In my layout there are 2 buttons for buying goods of two types, each of these purchases is bought once for each Google account. How can I check whether the purchase has already been purchased or not and withdraw the payment? Thank you.
I also heard that there are third-party libraries .. can I have their names and how to use them? Thanks a lot.

Answer 1

UPD 2017-09-28: Centuries
later, Google bothered to pack the billing tools in the form of an official library , now it's better to use it.
You need to copy certain classes from somewhere in the documentation (IabHelper, etc.) to work with billing, in general, the process is not very convenient. An example application is here . There is also a third-party library that simplifies the work with billing a little.