IAP / Purchasing Gradle errors

Symptoms:

• Gradle build errors on Andorid platform using Unity 4.12.0 and above
• Unity version 2020 and above

Cause:

In IAP 4.12.0, we updated to Google Play Billing Library 6 which introduced a new dependency which required us to support it.

Resolution:

1. Using EDM4U (External Dependency Manager for Unity)

• Verify if your project contains both EDM4U and MDR (Mobile Dependency Resolver). If it has both, remove MDR.
• In the Project Settings, under Player → Publishing Settings for Android,
  • enable  Custom Main Gradle Template 
  • enable Custom Gradle Properties Template 
• Go to Assets → External Dependency Manager → Android Resolver → Settings.
  • Enable Patch mainTemplate.gradle
  • Enable Copy and patch settingsTemplate.gradle from 2022.2
    *NB if the above settings aren't visible update your External Dependency Manager
• Go to Assets → External Dependency Manager → Android Resolver → Force Resolve

2. If your project has Google Mobile Ads and you are receiving this error:

Cannot change dependencies of dependency configuration ‘:unityLibrary:implementation’ after it has been included in dependency resolution.

In Assets → Google Mobile Ads → Settings

• Disable the Remove property tag from GMA Android SDK

3. If you get the following error:

java.lang.NoClassDefFoundError: Could not initialize class org.codehaus.groovy.vmplugin.v7.Java7

Go in Unity → Settings → External Tools, then disable and reenable the Android JDK, SDK and NDK.

More information:

https://discussions.unity.com/t/iap-4-12-0-solutions-to-android-build-issues/1503523