Another java-based multi-project build example. 1 java library project, 2 android library projects, 1 test project, 1 use of the actionbarsherlock apklib and 1 android project.

build.scala

import sbt._
import sbt.Keys._
import android.Keys._
import android.Dependencies.apklib

object ExampleMultiBuild extends Build {
  // add 'run' alias to the root project
  lazy val root = Project(id = "root-prj", base = file(".")) settings(
    android.Plugin.androidCommands ++ Seq(
      run   <<= (run in (mainprj, Android)) map { _ => Unit }): _*
  ) aggregate(javalib, alib, slidingmenu, mainprj)

  lazy val javalib = Project(id = "java-lib", base = file("AJavaLib")) settings(
    // use an ant/eclipse style layout
    javaSource in Compile <<= baseDirectory (_/"src"),
    javacOptions in Compile ~= { _ ++ Seq("-source", "1.5", "-target", "1.5") },
    // android projects consume java jars, export it with this setting
    exportJars := true
  )

  // our project has a weird layout, include guava from another project
  lazy val alib = Project(
    id = "andylib", base = file("AnAndroidLibrary")) settings((
	commonSettings :+ (unmanagedClasspath in Compile ~= {
        Attributed.blank(mainprj.base / "libs" / "guava-14.0.1.jar") +: _ })
  ):_*) dependsOn(javalib)

  // the main project loads actionbarsherlock via an apklib
  lazy val mainprj: Project = Project(
    id = "main", base = file("MainAndroidProject")) settings(Seq(
      resolvers <+= (sdkPath in Android) { p =>
        "gms" at (file(p) / "extras" / "google" / "m2repository").toURI.toString
      },
      libraryDependencies ++= Seq(
        apklib("com.actionbarsherlock" % "actionbarsherlock" % "4.2.0"),
        aar("com.google.android.gms" % "play-services" % "3.1.36")
      )

    ) ++ commonSettings: _*) dependsOn(alib, slidingmenu)

  lazy val tests = Project(
    id = "tests", base = file("SomeJvmBasedUnitTests")) settings(
    // this project has an eclipse/ant-style layout
    javaSource in Test <<= baseDirectory (_/"src"),
    libraryDependencies ++= Seq(
      "junit" % "junit" % "4.11" % "test",
      "com.novocode" % "junit-interface" % "0.10-M4" % "test"
    )
  ) dependsOn(mainprj)

  // another android library
  lazy val slidingmenu = Project(
    id = "smenu", base = file("SlidingMenu/library")) settings(
      commonSettings: _*)

  // this project configuration doesn't require specifying arguments to
  // androidBuild due to the way it's setup, but specifying them is harmless.
  lazy val commonSettings = android.Plugin.androidBuild :+
    (watchSources ~= { _.filterNot(_.isDirectory) })
}