Building a binding NuGet package does not include JAR files - use of the package results in `java.lang.NoClassDefFoundError`

[brunck]

Android framework version

net9.0-android

Affected platform version

VSCode 1.104.0, .NET 9.x, .NET 10.0.100-rc.1.25451.107

Description

The same problem as described in #9974 - dependent JAR files are not included in the NuGet package. AAR files are.
This is causing the same error and crash as described in the referenced issue when the binding NuGet is consumed - java.lang.NoClassDefFoundError

This happened using the .NET 9 SDK and earlier versions of VSCode so it’s not a .NET 10 regression per se.

This is a problem for package authors trying to update their packages to comply with the Google Play 16 KB requirement, which has a deadline coming.

Steps to Reproduce

Get the reproduction sample:

1. dotnet build -c Release
2. unzip -l ./bin/Release/com.yourcompany.SomeAndroidBinding.1.0.0.nupkg | grep kronos-java-0.0.1-alpha11.jar

Expected: The JAR file is included in the NuGet package and shown.
Actual: The JAR file is not included.

Note: running unzip -l ./bin/Release/com.yourcompany.SomeAndroidBinding.1.0.0.nupkg | grep kronos-android-0.0.1-alpha11.aar shows the AAR file as included.

[jonathanpeppers]

The fix for this is in .NET 10 RC 1, is it fixed for you there?

• [xabt] fix missing .nupkg output for dotnet pack #10270

[brunck]

@jonathanpeppers I noted above that I’m using .NET 10 RC 1 and I still see the problem.

Also if I use AndroidMavenLibrary I see the same problem, so I don’t think that 9974 was necessarily fixed, at least as far as I’m able to tell.

[jonathanpeppers]

The .jar files will have a hashed name like mentioned in the PR:

android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/XASdkTests.cs

Lines 164 to 169 in fca76a3

	// Look for libs/29CAF121D5FD8E3D.jar, libs/A1AFA985571E728E.jar
	using var aar = ZipArchive.Open (aarStream);
	int count = aar.Count (e =>
	e.FullName.StartsWith ("libs/", StringComparison.OrdinalIgnoreCase) &&
	e.FullName.EndsWith (".jar", StringComparison.OrdinalIgnoreCase));
	Assert.AreEqual (2, count, $"There should be 2 .jar files in the {aarPath} archive, but found {count}.");

Are you sure they aren't there when targeting net10.0-android?

[brunck]

Yes, I am sure. If you use the reproduction as provided and run the two commands I list, you’ll see that the JAR file is not included. You can set it to net10.0-android and still the problem remains. If I manually extract the .nupkg files, in the lib folder I still do not see the .jar file, just to double check the unzip command I provided.

[brunck]

@jonathanpeppers I assume you mean when inspecting the .aar file that is generated and is inside the package? That only has a proguard.txt file, no JAR files, when I look at it using a decompiler.
It does seem to work if .NET 10 is targeted, although that is not production-ready so we can't very well be releasing NuGet packages for use in production that target .NET 10.

[Domik234]

FYI

I had propably similar or same problem.

Basically I needed to pack also joda-time:joda-time package but without binding. My app crashed on start because of missing classes when I had this:
<AndroidMavenLibrary Include="joda-time:joda-time" Version="2.10.14" Bind="false" />

So I've added jar file downloaded from maven to Packages folder and did this:

<AndroidLibrary Remove="Packages\joda-time-2.10.14.jar" />
<AndroidJavaLibrary Include="Packages\joda-time-2.10.14.jar" Bind="False" />

This older Item Group makes the jar file work. It is added to the aar of the binding project and later available in the final app.
Microsoft Docs - Xamarin.Android binding project migration

I've also added record to proguard.cfg (may not be needed):

-keep class org.joda.time.** { *; }
-keep interface org.joda.time.** { *; }