Copy classes from 'core' module to other modules

build.gradle

//copy core classes to the project gen folder
def includeCoreClasses = { Project p ->
    p.android.libraryVariants.all { variant ->
        def outputDir = p.file("$p.buildDir/generated/core/${variant.dirName}")
        def packageName = variant.generateBuildConfig.appPackageName

        def mergeTask = p.tasks.create(name: "merge${variant.name.capitalize()}CoreClasses", type: Copy) {
            from(project(':core').android.sourceSets.main.java.srcDirs) {
                filter { String line ->
                    if (line == 'package ru.solodovnikov.rxlocationmanager') {
                        "package $packageName"
                    } else {
                        line
                    }
                }
                eachFile {
                    path = "${packageName.replaceAll('\\.', '/')}/$name"
                }
            }
            into outputDir
        }
        variant.registerJavaGeneratingTask mergeTask, outputDir
    }
}

project(':rxlocationmanager') {
    includeCoreClasses(it)
}

project(':rxlocationmanager-rxjava2') {
    includeCoreClasses(it)
}