# First create the file version.properties with value VERSION_BUILD=0
# In app/build.gradle:

android {
    def versionPropsFile = file('version.properties')
    def versionBuild

    if (versionPropsFile.canRead()) {
        def Properties versionProps = new Properties()
        versionProps.load(new FileInputStream(versionPropsFile))
        versionBuild = versionProps['VERSION_BUILD'].toInteger()
    } else {
        throw new FileNotFoundException("Could not read version.properties!")
    }

    ext.autoIncrementBuildNumber = {
        if (versionPropsFile.canRead()) {
            def Properties versionProps = new Properties()
            versionProps.load(new FileInputStream(versionPropsFile))
            versionBuild = versionProps['VERSION_BUILD'].toInteger() + 1
            versionProps['VERSION_BUILD'] = versionBuild.toString()
            versionProps.store(versionPropsFile.newWriter(), null)
        } else {
            throw new FileNotFoundException("Could not read version.properties!")
        }
    }

    # Add / change this part in defaultConfig for the versionCode
    defaultConfig {
        versionCode versionBuild
    }

    gradle.taskGraph.whenReady { taskGraph ->
        if (taskGraph.hasTask(assembleDebug)) {
            autoIncrementBuildNumber()
        } else if (taskGraph.hasTask(assembleRelease)) {
            autoIncrementBuildNumber()
        }
    }
}