[Android Gradle] Auto-Increment version code/name in AndroidManifest/Gradle before Jenkins Build

jenkins_android_gradle_buildNum

import java.util.regex.Pattern

def versionMajor = 1
def versionMinor = 0
def versionPatch = 0

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.jakewharton.sdkmanager:gradle-plugin:0.12.0'
    }
}

apply plugin: 'android-sdk-manager'
apply plugin: "com.android.application"

android {
    compileSdkVersion project.ANDROID_BUILD_SDK_VERSION
    buildToolsVersion project.ANDROID_BUILD_TOOLS_VERSION

    defaultConfig {
        applicationId project.APPLICATION_ID
        minSdkVersion project.ANDROID_BUILD_MIN_SDK_VERSION
        targetSdkVersion project.ANDROID_BUILD_TARGET_SDK_VERSION

        def vCode
        def vName
        def vItem

        def buildNum = System.getenv("BUILD_NUMBER") ?: 0
        if (buildNum != 0) {
            vItem = buildNum.toInteger()
        } else {
            vItem = versionPatch
        }

        versionCode versionMajor * 10000 + versionMinor * 1000 + vItem * 100
        versionName "${versionMajor}.${versionMinor}.${vItem}"
    }

    buildTypes {
        debug {
            applicationIdSuffix ".debug"
            minifyEnabled false
            debuggable true
            testCoverageEnabled true

            applicationVariants.all { variant ->
                variant.outputs.each { output ->
                    def buildNum = System.getenv("BUILD_NUMBER") ?: 0

                    if (buildNum != 0) {
                        def manifestFile = file("src/main/AndroidManifest.xml")

                        def pattern = Pattern.compile("versionCode=\"(\\d+)\"")
                        def pattern2 = Pattern.compile("versionName=\"(.*?)\"")

                        def manifestText = manifestFile.getText()

                        def matcher = pattern.matcher(manifestText)
                        matcher.find()

                        def manifestContent = matcher.replaceAll("versionCode=\"" + buildNum + "\"")

                        def matcher2 = pattern2.matcher(manifestContent)
                        matcher2.find()

                        def manifestContent2 = matcher2.replaceAll("versionName=\"" + "${versionMajor}.${versionMinor}." + buildNum + "\"")

                        manifestFile.write(manifestContent2)

                        def file = output.outputFile
                        def newfilename = file.name.replace(".apk", "-" + buildNum + ".apk")
                        output.outputFile = new File(file.parent, newfilename)
                    }
                }
            }
        }
    }
}