# Troubleshooting In-App Purchasing 5.4.0 Android builds on Unity 2022.3

> Solve an Android build failure when you use In-App Purchasing 5.4.0 on Unity 2022.3 LTS.

In-App Purchasing (IAP) 5.4.0 is designed for Unity 6. To use IAP 5.4.0 with Unity 2022.3 LTS on Android, you need to adjust some project settings.

This page explains why the build fails on Unity 2022.3, how to recognize the errors, and the steps to build successfully. The steps are verified against Unity 2022.3.62f2, but they apply to Unity 2022.3 LTS in general.

> **Note:**
>
> For new projects, and to avoid this configuration entirely, use Unity 6, where IAP 5.4.0 builds without changes. If you're staying on Unity 2022.3 for now, you can use this page to adopt IAP 5.4.0 today, and then you can plan a move to Unity 6 at your own pace.

## Symptoms

Depending on your build settings, IAP 5.4.0 on Unity 2022.3 can fail during the Android build with one or more of the following errors. If you get these errors, apply the steps in the [Resolution](#resolution) section.

* A manifest merge error such as `uses-sdk:minSdkVersion 22 cannot be smaller than version 23 declared in library [com.android.billingclient:billing:9.0.0]`.
* An R8 error during the minify step, for example `R8: java.lang.NullPointerException` with an origin of `androidx.core` (`core-1.15.0-runtime.jar`).
* A duplicate class failure from `checkDebugDuplicateClasses` or `checkReleaseDuplicateClasses`, involving either `androidx.core` / `android.support.v4` or `kotlin-stdlib` (for example `Duplicate class kotlin.collections.jdk8.CollectionsJDK8Kt`).

## Cause

IAP 5.4.0 depends on Google Play Billing Library 9.0.0, which in turn requires `androidx.core` 1.15.0. `androidx.core` 1.15.0 is built for Android Gradle Plugin 8 and later.

Unity 2022.3 LTS builds with Android Gradle Plugin 7.4.2 (Gradle 7.5.1). This older plugin and its R8 compiler can't process `androidx.core` 1.15.0, which produces the R8 and duplicate class errors above. Google Play Billing Library 9.0.0 also requires a minimum Android API level of 23, which is higher than the Unity default.

The following steps keep IAP 5.4.0 and Google Play Billing Library 9.0.0 in place, and align the affected Android dependencies with versions the Unity 2022.3 toolchain can build.

## Resolution

To build IAP 5.4.0 on Unity 2022.3, follow these steps:

1. [Set the minimum API level to 23 or higher](#set-the-minimum-api-level-to-23-or-higher)
2. [Pin the Android dependencies with a custom Gradle template](#pin-the-android-dependencies-with-a-custom-gradle-template)
3. [Build your project](#build-your-project)

### Set the minimum API level to 23 or higher

1. Go to **Edit** > **Project Settings** > **Player** > **Android** > **Other Settings**.
2. Set **Minimum API Level** to **Android 6.0 'Marshmallow' (API level 23)** or higher.

This satisfies the minimum API level required by Google Play Billing Library 9.0.0.

### Pin the Android dependencies with a custom Gradle template

1. Go to **Edit** > **Project Settings** > **Player** > **Android** > **Publishing Settings**.
2. Under **Build**, enable **Custom Base Gradle Template**. Unity creates the file at `Assets/Plugins/Android/baseProjectTemplate.gradle`.
3. Open `baseProjectTemplate.gradle` and add the following block at the end of the file:

```gradle
allprojects {
    configurations.all {
        resolutionStrategy {
            // androidx.core 1.15.0 requires Android Gradle Plugin 8;
            // pin to the last release compatible with the Unity 2022.3 toolchain.
            force 'androidx.core:core:1.13.1'
            force 'androidx.core:core-ktx:1.13.1'
            // Align the Kotlin standard library to a single version to avoid duplicate classes.
            force 'org.jetbrains.kotlin:kotlin-stdlib:1.8.22'
            force 'org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.8.22'
            force 'org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.8.22'
        }
    }
}
```

Keep **Custom Base Gradle Template** enabled. The dependency versions only apply while Unity builds with this template.

### Build your project

Build for Android as usual (**File** > **Build Settings** > **Android** > **Build**). The build now completes past the minify and duplicate class checks.

## Move to Unity 6

The steps above are a supported way to build IAP 5.4.0 on Unity 2022.3, but they hold two Android dependencies below the versions the package targets. Unity 6 ships Android Gradle Plugin 8 and later, so IAP 5.4.0 builds without any of these changes. If you're planning an engine upgrade, moving to Unity 6 removes the need for this configuration.