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Distributing bindings libraries

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Once a Java library has been bound to be used in .NET for Android, there are multiple ways it can be consumed:

  • Project Reference - If the binding project and the application project are in the same solution file, using a <ProjectReference> is generally the easiest way to consume the binding.

  • NuGet Package - A NuGet package is ideal for public publishing or for an internal distributed development environment that has an internal NuGet server.

  • File Reference - A consuming application can directly add a <Reference> to a binding .dll if neither the binding project nor a NuGet server is available.

Controlling binding and packaging options

A bindings library project has two options for controlling if an <AndroidLibrary> gets bound and gets redistributed:

  • Bind (true/false) - Defaults to true, meaning managed bindings are created for the specified <AndroidLibrary>. Setting to false means the Java library will be included in the output, but will not have managed bindings. This is useful if the library a needed dependency of another Java library, but it will not be called from C#.
<!-- Java library will have C# bindings and be included in the output -->
<AndroidLibrary Include="okhttp-4.12.0.jar" />

<!-- Java library will not have C# bindings but will still be included in the output -->
<AndroidLibrary Include="okio-3.9.0.jar" Bind="false" />
  • Pack (true/false) - Defaults to true, meaning the specified <AndroidLibrary> will be included in the output (such as a NuGet package). Setting to false means the Java library will not be included in the output. This is a rare scenario in case the dependency is already being provided via alternative means.
<!-- Java library will have C# bindings and be included in the output -->
<AndroidLibrary Include="okhttp-4.12.0.jar" />

<!-- Java library will have C# bindings but will *not* be included in the output -->
<AndroidLibrary Include="okio-3.9.0.jar" Pack="false" />

ProjectReference

If the binding project and the application project are in the same solution file, using a <ProjectReference> is generally the easiest way to consume the binding:

<ProjectReference Include="mybindinglib.csproj" />

The build system will be responsible for adding the managed bindings as well as any .jar/.aar files to the application project.

NuGet package

As a property inherited from .NET SDK-style projects, any bindings library can be trivially packaged into a redistributable NuGet package by using the "Pack" command in Visual Studio or from the command line:

dotnet pack

The bindings library as well as the Java library will be included in the NuGet package:

NuGet package contents

Use the Pack attribute documented above to control which Java libraries are desired in the NuGet package.

NuGet packages can be customized using the standard .NET MSBuild elements.

File reference

If neither of the above options are possible, the binding .dll can be referenced directly with a <Reference> element. Note that any Java libraries that are part of the binding project output must be in the same directory as the binding .dll.

If you move/copy just the binding .dll to another location and do not also move/copy any .jar/.dll files they will not end up in your application and the binding will fail at runtime.

Important

In Classic Xamarin.Android using an item action like EmbeddedJar would place the .jar file inside the .dll and only one file would be needed. Support for this was removed in .NET for Android because it greatly increased application build time to scan and extract embedded Java library files. Any needed .jar/.dll files MUST be located in the same directory as the binding .dll.