Xamarin.Android provides open-source bindings of the Android SDK for use with .NET managed languages such as C#.

The Xamarin.Android build is heavily dependent on MSBuild, with the intention that it should (eventually?) be possible to build the project simply by checking out the repo, loading Xamarin.Android.sln into an IDE, and Building the solution. (This isn't currently possible, and may never be, but it's the vision.)

However, some properties may need to be altered in order to suit your requirements, such as the location of a cache directory to store the Android SDK and NDK.

To modify the build process, copy [Configuration.Override.props.in][Configuration.Override.props.in] to Configuration.Override.props, and edit the file as appropriate. Configuration.Override.props is <Import/>ed by Configuration.props and will override any default values specified in Configuration.props.

Overridable MSBuild properties include:

• $(AndroidApiLevel): The Android API level to bind in src/Mono.Android.
• $(AndroidFrameworkVersion): The Xamarin.Android $(TargetFrameworkVersion) version which corresponds to $(AndroidApiLevel).
• $(AndroidToolchainCacheDirectory): The directory to cache the downloaded Android NDK and SDK files. This value defaults to $(HOME)\android-archives.
• $(AndroidToolchainDirectory): The directory to install the downloaded Android NDK and SDK files. This value defaults to $(HOME)\android-toolchain.
• $(HostCc), $(HostCxx): The C and C++ compilers to use to generate host-native binaries.

Building Xamarin.Android requires the Java Development Kit (JDK), several pieces of the Android SDK, and the Android NDK.

The Java Development Kit may be downloaded from the Oracle Java SE Downloads page.

To simplify building Xamarin.Android, important pieces of the Android SDK and Android NDK will be automatically downloaded and installed from Google's website. Downloaded files are cached locally, by default into $(AndroidToolchainDirectory). The Android NDK and SDK will be installed by default into $(AndroidToolchainDirectory).

The files that will be downloaded and installed are controlled by build-tools/android-toolchain/android-toolchain.projitems via the @(AndroidNdkItem) and @(AndroidSdkItem) item groups, and the URL to download files from is controlled by the $(AndroidUri) property.

At this point in time, building Xamarin.Android is only supported on OS X. We will work to improve this.

To build Xamarin.Android, first prepare the project:

make prepare

This will perform git submodule update, and any other pre-build tasks that need to be performed.

Then, you may do one of the following:

1. Run make:

    make
   

2. Load Xamarin.Android.sln into Xamarin Studio and Build the project.

   Note: The Mono.Android project may fail on the first build because it generates sources, and those sources won't exist on the initial project load. Rebuild the project should this happen.

There are two configurations, Debug and Release, controlled by the $(Configuration) MSBuild property.

The bin\Build$(Configuration) directory, e.g. bin\BuildDebug, contains artifacts needed for building the repository. They should not be needed for later execution.

The bin\$(Configuration) directory, e.g. bin\Debug, contains redistributable artifacts, such as tooling and runtimes. This directory acts as a local installation prefix, in which the directory structure mirrors that of the OS X Xamarin.Android.framework directory structure:

• bin\$(Configuration)\lib\xbuild\Xamarin\Android: MSBuild-related support files and required runtimes used by the MSBuild tooling.
• bin\$(Configuration)\lib\xbuild-frameworks\MonoAndroid: Xamarin.Android profiles.
• bin\$(Configuration)\lib\xbuild-frameworks\MonoAndroid\v1.0: Xamarin.Android Base Class Library assemblies such as mscorlib.dll.
• bin\$(Configuration)\lib\xbuild-frameworks\MonoAndroid\*: Contains Mono.Android.dll for a given Xamarin.Android $(TargetFrameworkVersion).

Xamarin.Android uses the MSBuild $(TargetFrameworkVersion) mechanism to provide a separate Mono.Android.dll binding assembly for each API level.

This means there is no single Mono.Android.dll, there is instead a set of them.

This complicates the "mental model" for the Mono.Android project, as a project can have only one output, not many (...within reason...). As such, building the Mono.Android project will only generate a single Mono.Android.dll.

To control which API level is bound, set the $(AndroidApiLevel) and $(AndroidFrameworkVersion) properties. $(AndroidApiLevel) is the Android API level, usually a number, while $(AndroidFrameworkVersion) is the Xamarin.Android $(TargetFrameworkVersion).

The default values will target Android API-23, Android 6.0.

For example, to generate Mono.Android.dll for API-19 (Android 4.4):

cd src/Mono.Android
xbuild /p:AndroidApiLevel=19 /p:AndroidFrameworkVersion=v4.4
# creates bin\Debug\lib\xbuild-frameworks\MonoAndroid\v4.4\Mono.Android.dll