The Android implementation of in_app_purchase.
This package is endorsed, which means you can simply use in_app_purchase normally. This package will be automatically included in your app when you do, so you do not need to add it to your pubspec.yaml.
However, if you import this package to use any of its APIs directly, you should add it to your pubspec.yaml as usual.
Alternative and UserChoice billing from Google Play is exposed from this package.
Using the Alternative billing only feature requires Google Play app configuration, checking if the feature is available (isAlternativeBillingOnlyAvailable) and informing users that Google Play does not handle all aspects of purchase (showAlternativeBillingOnlyInformationDialog). After those calls then you can call setBillingChoice and respond when a user attempts a purchase.
Google Play documentation for Alternative billing
To migrate to version 0.3.0 from 0.2.x, have a look at the migration guide.