How to implement the purchase of additional functionality in the application?

Question

Android

Please tell me how to implement the purchase in the application of additional functionality.
There are two types in the play markete:
1) Purchase of an additional application (key)
2) Purchase within the application
Please describe the pros and cons of implementing each method.
And I would be very grateful for links to implementation examples.

Answer 1

dev.android.com - there is even an example of a working application, what else do you need???
If English is tight, then look on other resources where it is written in Russian, in a minute you can find dozens of articles on this topic.

Answer 2

I would like to say a few words about in-app purchases. This implementation of the purchase add. functionality in the application is convenient, but unreliable. If the device is rooted, then bypassing the protection system through other programs will not be difficult, but if the purchase comes from GooglePlay itself, then it is much more difficult to bypass the protection system there.