Gradle Warning "not specified, depends on libraries, but is a jar" when compiling the android module in the user module of the java library

Question

I am new to Gradle. I have a simple project structure (see below) with the main Android application module, one Android module (myandroidlibrary) and one pure java module (myjavalibrary). They have simple dependencies, app → myjavalibary, myjavalibary → myandroidlibrary (see Figure below). Below are snapshots of Gradle files.

However, when synchronizing Gradle, it throws the following error:

D:\MyTestCodes\MyTestApplication\app\build.gradle Warning:Module version MyTestApplication:myjavalibrary:unspecified depends on libraries but is a jar 

Help me! I spent all this day to deal with this to no avail!

 MyProject - app - myjavalibrary (pure java library) - myandroidlibrary (android library) 

Now the dependency is as follows:

 "app" depends on -> "myjavalibrary" "myjavalibrary" depends on -> "myandroidlibrary" 

Gradle files for each of the modules:

 gradle file for app module: ---------------------------- apply plugin: 'com.android.application' android { // ommitting other detail dependencies { compile fileTree(dir: 'libs', include: ['*.jar']) compile 'com.android.support:appcompat-v7:22.0.0' compile project(':myjavalibrary') } Gradle file for myjavalibrary module: ------------------------------------- apply plugin: 'java' dependencies { compile fileTree(dir: 'libs', include: ['*.jar']) compile project(':myandroidlibrary') } gradle file for myandroidlibrary module: ---------------------------- apply plugin: 'com.android.application' android { //ommiting other detail. dependencies { compile fileTree(dir: 'libs', include: ['*.jar']) compile 'com.android.support:appcompat-v7:22.0.0' } The settings.gradle: --------------------- include ':app', ':myjavalibrary', ':myandroidlibrary' 

Now when I sync Gradle files, it shows the following error:

  D:\MyTestCodes\MyTestApplication\app\build.gradle Warning:Module version MyTestApplication:myjavalibrary:unspecified depends on libraries but is a jar 

Answer 1

The warning is triggered by the pure-jave myjavalibrary myjavalibrary , which has a dependency on myandroidlibrary one, which is the Android library.

Gradle warns you that the pure-java module does not know anything about Android-specific myandroidlibrary tags (such as Android resources, assets, etc.). Having this dependency (pure-java for the android library), you may lose some of the things you expect.

A clearer direction of dependencies would be from the android library to the pure-java library. In this case, Gradle will not give you any warnings.

Answer 2

If you want to create an Android application project from Java code, use apply plugin: 'com.android.application' .

If you want to create a library project from java code, use apply plugin: 'com.android.library' .

If you want to use pre-created jar files, do not create any project for them. Just add them to the projects, in the libs folder, which depend on them. compile fileTree(dir: 'libs', include: ['*.jar']) in dependencies will take care of them.