(This is similar to Requiring a minimum version of the Android NDK, but for SDK versions)

Again, I was tinkering with our build system at work, which is a set of small Makefiles that are responsible for invoking ndk-build (to build our C component) and ant (for the Java component). These files also maintain the dependency graph for the cross-domain dependencies, so things like header files being generated from class-files using javah and APKs depending on the produced shared libraries.

I recently made some changes to the ant build step by creating our own custom_rules.xml, exposing the “hidden” -compile target. What I noticed was that build.xml only did an <import file="custom_rules.xml" optional="true" /> if you were on a fairly recent Android SDK version. This isn’t a problem for our Jenkins builds, since we’ve got an in-house system that ensures a strict version dependency between a specific source checkout and SDK/NDK versions, so they were always using the newer SDK. It was a problem for our developers – we’ve yet to roll this system to our development machines, so developers are responsible for checking out and updating their own SDKs.

To prevent this from getting in the way, I wrote a little snippet of bash that’s run from the Makefile, that ensures that the SDK version is at least the given version.

You can find the shellscript as a gist on GitHub

Put the script into assert_sdk_version.sh, and put the following at the top of your Makefile, and voilà! Builds should now fail with a more understandable message if someone’s using the wrong NDK version. :–)

Makefile
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ifneq ($(shell $(LOCAL_PATH)/assert_sdk_version.sh "r19"),true)
  $(error SDK version r19 or greater required)
endif

If you’re curious how this works: It checks the tools/source.properties file in your Android SDK, looking for a line like Pkg.Revision=XX, and extracts the version (XX) from that.

It’s pretty straight forward, but I couldn’t find anything online on how to check the SDK version from the command line, so I figured I’d share it.

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