Android Gradle Build System: Create Jar Not Library

Question

Currently I am working in eclipse. I want to migrate to Android Studio however I need to figure this out first: How do I create a jar for my project using the new android build system?

My Project is setup as a library however there are only java files in the project. I don't need or want to export this as a library. I want to export the files as a .jar so it can easily be dropped into another project.

Update Here is my gradle file. I cannot add the line apply plugin java because it is incompatible with the android plugin. The jar task is already included in the android plugin.

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.4'
    }
}
apply plugin: 'android'

dependencies {
    compile files('libs/android-support-v4.jar')
}

android {
    compileSdkVersion 17
    buildToolsVersion "17.0.0"

    defaultConfig {
        minSdkVersion 7
        targetSdkVersion 16
    }
}

sourceSets {
    main  {
        java {
            srcDir 'src/main/java'
        }
    }
}
task jar(type: Jar) {
    from sourceSets.main.java
}

I'm running the script as: gradle clean jar

When I run the tasks, nothing happens... Why? What am I missing?

Update 2

Below is the new gradle build file that I'm using. Notice the gradle version change due to android studio's latest update. Even with a simple clean build I get this error: Project directory '<my_workspace_path>\Core2Project\build.gradle' is not a directory. This error only happens in the build studio. Not when I run from the IDE. I've run into this same issue with another project as well. Turns out i'll get this error when I specify the file name to use in the build studio.

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.5.+'
    }
}
apply plugin: 'android'

dependencies {
    compile files('libs/android-support-v4.jar')
}

android {
    compileSdkVersion 17
    buildToolsVersion "17.0.0"

    defaultConfig {
        minSdkVersion 7
        targetSdkVersion 16
    }

    sourceSets {
        main  {
            java {
                srcDir 'src/main/java'
            }
        }
    }
}


task jar(type: Jar) {
    from android.sourceSets.main.java
}

Reversion

Answer 1

With newer versions of gradle and the android gradle plugin, you just need to add the following to your build.gradle:

task jar(type: Jar) {
    from android.sourceSets.main.java.srcDirs
}

and run gradle clean compileReleaseJava jar

On older versions of the gradle plugin, your sourceSets element needs be inside android:

android {
    compileSdkVersion 17
    buildToolsVersion "17.0.0"

    defaultConfig {
        minSdkVersion 7
        targetSdkVersion 16
    }

    sourceSets {
        main  {
            java {
                srcDir 'src/main/java'
            }
        }
    }
}

Then, your jar task would need to reference android.sourceSets:

task jar(type: Jar) {
    from android.sourceSets.main.java
}

Sleety

I want to say you're right, but I can't build my project anymore. Just a simple "clean build" gives me an error. The build.gradle file in the error path is the one i'm pointing to in order to run the tasks. No changes here. Project directory '<my_workspace_path>\Core2Project\build.gradle' is not a directory. – Reversion

are you on the latest gradle plugin version? you should be at classpath 'com.android.tools.build:gradle:0.5.+' now – Sleety

Yes, I actually created a new project just now and copied my src directory, and the android and jar bits from the gradle. My build script is inside of the module's gradle file, not the project's gradle file – Reversion

why are you pointing to that error path to run the tasks? what are you trying to run? – Sleety

I guess I left it that way because that's how it is set by default. The build targets the Project level gradle file (which has a settings file next to it that pulls in each module's gradle file. This case there is only one module) – Reversion

Even when I change it to point to the module's build file I see the same error (with the relevant path) – Reversion

With the latest Gradle plugin, I had to change the Jar task body from part to this: from fileTree(dir: 'build/intermediates/classes/release') I also run gradle clean compileReleaseJava jar – Luncheon

More recently: from android.sourceSets.main.java.srcDirs – Mamie

Do we add the task to the project-level or the module-level build.gradle? – Thunderous

Answer 2

the 'jar' task you mean here is introduced by the java plugin. you can apply the gradle java plugin by using

apply plugin:'java'

Have a look in the chapter about the java plugin in the gradle userguide at http://www.gradle.org/docs/current/userguide/tutorial_java_projects.html#N103C6 to get more information about the java plugin.

cheers,

René

Redpencil

that's surprising as the java library definitely adds a jar task. can you provide the full rootproject build file. What do you mean with "using" the jar task? injecting it from the command line? – Redpencil

Sorry for the delay, I've updated my question with the build script – Reversion

what do you mean by "nothing happens" when running "gradle clean jar" is the task executed and marked as up-to-date? Is no jar file created in build/libs? One thing I notice in your build script is the configuration of your main java source directory. This is the default I think so configuring this isn't necessary. Furthermore, your snippet just adds another directory to the default ones. – Redpencil

The java plugin doesn't compile correctly against imported android classes. – Sleety