Java.Lang.ClassNotFoundException Didn't find class "androidx.core.splashscreen.SplashScreen" on path: DexPathList

Question

Java.Lang.ClassNotFoundException Didn't find class "androidx.core.splashscreen.SplashScreen" on path: DexPathList

Kim Strasser 1,321

I get the following error in Activity1.cs in my Android project:

protected override void OnCreate(Bundle bundle)
{
    AndroidX.Core.SplashScreen.SplashScreen.InstallSplashScreen(this);

Java.Lang.ClassNotFoundException Message=Didn't find class "androidx.core.splashscreen.SplashScreen" on path: DexPathList[[zip file "/data/app/~~8NjzDRCJ5Z5JiKWZbb1ewA==/com.myname.appname-vHE02keTTv4yXDk6G-jBSg==/base.apk"],nativeLibraryDirectories=[/data/app/~~8NjzDRCJ5Z5JiKWZbb1ewA==/com.myname.appname-vHE02keTTv4yXDk6G-jBSg==/lib/arm64, /data/app/~~8NjzDRCJ5Z5JiKWZbb1ewA==/com.myname.appname-vHE02keTTv4yXDk6G-jBSg==/base.apk!/lib/arm64-v8a, /system/lib64, /system/system_ext/lib64]]

The error came after installing/uninstalling the NuGet package Xamarin.Firebase.Crashlytics (119.3.0).

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Answer 1

Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Microsoft External Staff

Hello,

androidx.core.splashscreen.SplashScreen is not a native component included with Maui. You need to install Xamarin.AndroidX.Core.SplashScreen to use this API.

Best Regards,

Alec Liu.

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Kim Strasser 1,321 Reputation points

2025-01-13T10:13:30.5566667+00:00

Xamarin.AndroidX.Core.SplashScreen (1.0.1.13) is already installed. I have tried to uninstall it and installed it again and made a clean&rebuild on my Android project but I still get the same error.
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Reputation points Microsoft External Staff

2025-01-14T05:37:39.72+00:00

Thanks for your feedback.

I noticed that you created a Maui project for .net 9.0. In this project, the Nuget Packages with yellow exclamation marks have not been officially released for .net 9.0.

Therefore, this should be an error caused by Nuget Package dependency conflicts. If you use a .net 8.0 project to install these packages and call this API, will the problem occur?

Your prompt reply will be highly appreciated.
Kim Strasser 1,321 Reputation points

2025-01-15T00:16:29.9433333+00:00

Two weeks ago it still worked with target framework .NET 9 because I had created an archive in release mode for Google Play internal testing.

Clean&Rebuild the project and delete the obj and bin folder doesn´t solve the problem.

In addition, I get this warning:

1>obj\Debug\net9.0-android\proguard\proguard_project_references.cfg : warning XA4304: ProGuard configuration file 'obj\Debug\net9.0-android\proguard\proguard_project_references.cfg' was not found.

I don´t know if this warning was already there before I got the Java.Lang.ClassNotFoundException or if this warning is new.
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Reputation points Microsoft External Staff

2025-01-15T05:32:38.3633333+00:00

Thanks for your feedback.

For XA4304 warning, you can refer to this official solution.

Solution Verify you are not declaring a ProguardConfiguration build item that does not exist. Consider submitting a bug if you are getting this warning under normal circumstances.

If I create a new project, are there specific steps to reproduce this problem?
Kim Strasser 1,321 Reputation points

2025-01-15T13:19:07.2133333+00:00
I have a file named proguard.cfg in my Android project and the Build Action of this file is set on ProguardConfiguration.

-dontobfuscate

-dontwarn com.google.android.gms.** -keep class com.google.android.gms.** { ; } -keep class com.google.firebase.* { *; } -ignorewarnings

And in MyAppAndroid.csproj I have this:

<ItemGroup> <ProguardConfiguration Include="proguard.cfg" /> </ItemGroup>

Is this proguard_project_references.cfg a different proguard file?

I don´t get this warning when I create a new .Net9 Android project.
Kim Strasser 1,321 Reputation points

2025-01-15T23:33:41.3966667+00:00

I have uninstalled Maui.Controls, Maui.Core, Maui.Essentials and all the Xamarin. NuGet packages and then I have installed the Maui packages and then the Xamarin packages again. Then I have deleted the obj and bin folder and made a clean&rebuild on my Android project. But I still get the same Java.Lang.ClassNotFoundException.

Current NuGet packages:
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Reputation points Microsoft External Staff

2025-01-16T05:52:55.9566667+00:00

Thanks for your feedback.

I installed the same project as the Nuget Package list you showed and compiled it with Visual Studio 2022 17.12.0. As a result, this error did not occur. Therefore, this problem may be caused by accidental damage to your project file. You can try to create a new Maui project and reinstall these Nuget Packages.

Kim Strasser 1,321

I found out that I don´t get the Java.Lang.ClassNotFoundException when I remove the following line from my csproj file:

  <AndroidLinkTool>r8</AndroidLinkTool>

Can I remove this line from my Android csproj file?

Android csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net9.0-android</TargetFramework>
    <SupportedOSPlatformVersion>31.0</SupportedOSPlatformVersion>
    <OutputType>Exe</OutputType>
    <ApplicationId>com.companyname.AndroidProj</ApplicationId>
    <ApplicationVersion>1</ApplicationVersion>
    <ApplicationDisplayVersion>1.0</ApplicationDisplayVersion>
    <AndroidSigningKeyStore>androidkeystore.keystore</AndroidSigningKeyStore>
    <AndroidEnableR8>true</AndroidEnableR8>
    <AndroidLinkTool>r8</AndroidLinkTool>
    <AndroidSupportedAbis>armeabi-v7a;arm64-v8a;x86;x86_64</AndroidSupportedAbis>
    <DebugType>portable</DebugType>
    <DebugSymbols>true</DebugSymbols> 
    <AndroidLinkMode>SdkOnly</AndroidLinkMode>
  </PropertyGroup>
...

Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 50,126 Reputation points Microsoft External Staff

2025-01-24T05:59:31.7833333+00:00
Thanks for your feedback.

r8 is a code shrinker that uses an aggressive strategy. Using this optimizer may indeed cause java.lang.ClassNotFoundException. Therefore, it is specifically mentioned in the official blog that r8 is only recommended in Release mode.

 <AndroidLinkTool Condition="'$(Configuration)' == 'Release'">r8</AndroidLinkTool>

Therefore, this should be a problem caused by the optimization strategy. For more details, please refer to this official blog.

R8 Java Code Shrinker.

Kim Strasser 1,321

It works in debug mode with this code. I have not tested in release mode.

<AndroidEnableR8>true</AndroidEnableR8>      
<!-- NOTE: not recommended for Debug builds! -->       
<AndroidLinkTool Condition="'$(Configuration)' == 'Release'">r8</AndroidLinkTool>

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Java.Lang.ClassNotFoundException Didn't find class "androidx.core.splashscreen.SplashScreen" on path: DexPathList

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