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.

Read time 4 minutes

Last updated 2 months ago

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 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

checkReleaseDuplicateClasses

, involving either

androidx.core

android.support.v4

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:

Set the minimum API level to 23 or higher
Pin the Android dependencies with a custom Gradle template
Build your project

Set the minimum API level to 23 or higher

Go to Edit > Project Settings > Player > Android > Other Settings.
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

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


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.

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