It can be tricky sometimes when adding an android library project in intellij or android studio. The reasons may vary from time to time but two I recently encountered are:

1. Automatic update of project.properties is disabled in intellij, thus the android library project cannot be added.
2. Creating a new library module in android studio, for an ant based project, Studio only creates a settings.gradle, but forget to change the project.properties.

So far, the root cause is clear, the inconsistency between ide settings and android configs.

1. You can manually update project.properties to a correct value

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target=android-16
android.library.reference.1=../../actionbarsherlock

and

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android.library=true
target=android-14

1. Remember to update settings in your IDE

That’s it.