Android Gradle build with sub projects

Question

I am currently in the process of converting one of our projects to Gradle from maven. The folder structure is as follows:

gitRoot
    settings.gradle
    build.gradle
    ProjectA
        build.gradle
        src/main/java
    Libraries
        SomeLib (git submodule)
        ProjectBRoot (git submodule)
            settings.gradle
            build.gradle
            ProjectB
                build.gradle
                src/main/java
            Libraries
                FacebookSDK/facebook
                    build.gradle
                    src

So already it looks complicated. But the idea is that ProjectB is a library project and it should be able to be built and packaged separately, which is why it has its own settings.gradle and as far as i can tell it seems to be working ok, i have it building and its finding facebook just fine.

The ProjectB/build.gradle contains this line

compile project(':libraries:facebook-android-sdk:facebook')

The ProjectBRoot/settings.gradle contains this line

include ':ProjectB', ':libraries:facebook-android-sdk:facebook'

The gitRoot/settings.gradle contains this line

include ':ProjectA', ':Libraries:ProjectBRoot:ProjectB'

The ProjectA/build.gradle contains this line

compile project(':Libraries:ProjectBRoot:ProjectB')

When I run the build i get this error

The TaskContainer.add() method has been deprecated and is scheduled to be removed in Gradle 2.0. Please use the create() method instead.

FAILURE: Build failed with an exception.

* Where:
Build file '/gitRoot/Libraries/ProjectBRoot/ProjectB/build.gradle' line: 17

* What went wrong:
A problem occurred evaluating project ':Libraries:ProjectBRoot:ProjectB'.
> Project with path ':libraries:facebook-android-sdk:facebook' could not be found in project ':Libraries:ProjectBRoot:ProjectB'.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 4.652 secs

So my guess as to whats wrong is that facebook is not in a direct subfolder from ProjectB...but that doesn't matter when building within ProjectBRoot. This is probably due to the face that I am referencing ProjectB directly and not through the ProjectBRoot/gradle.build but I tried that and it also did not work. Can someone please help me out, I have looked through the documentation and it doesn't talk about multiple projects that have their own settings.gradle files and I think thats the thing that is messing me up.

Update:

So I followed Xav's answer and I am now able to build with the command line however i can't import/build with android studio. I know the problem is still with the facebook project. The error i get is that it could not configure ProjectB.

 Gradle: A problem occurred configuring project ':ProjectA'.
   > Failed to notify project evaluation listener.
     > A problem occurred configuring project ':Libraries:ProjectBRoot:ProjectB'.
       > Failed to notify project evaluation listener.
         > Configuration with name 'default' not found.

The error is caused by the line

 compile project(':facebook-sdk')

inside the ProjectB/build.gradle

Answer 1

settings.gradle must define all the modules. It won't load other settings.gradle found in the tree to load more module.

You'll have to either

1. define a module for the facebook SDK in the top level settings.gradle. Yes it's redundant with the other settings.gradle.

2. publish Project B somehow (as well as its dependencies so in this case the facebook SDK library), somewhere (a corporate artifact repository for instance) and access it from Project A.

While #1 is better, it makes the ProjectB -> Facebook dependency tricky as the path will be different depending on the settings.gradle used. One way to fix this is to split the module name/path from its actual location on disk. this is done inside the settings.gradle file.

In your top level settings.gradle file, do

include 'facebook-sdk'
project(':facebook-sdk').projectDir = new File('Libraries/ProjectBRoot/Libraries/FacebookSDK/facebook')

In the setting.gradle file inside your Project B, do the same with the different relative path:

include 'facebook-sdk'
project(':facebook-sdk').projectDir = new File('Libraries/FacebookSDK/facebook')

This makes both project setup define the same 'facebook-sdk' module located at the same absolute location on disk.

All projects depending on this module should just declare the dependency as

compile project(':facebook-sdk')