how to update gradle version android code example

Example: how to auatomatically update version code in android gradle

android {
    compileSdkVersion 27
    buildToolsVersion '27.0.3'

    def versionPropsFile = file('version.properties')
    def value = 0
    Properties versionProps = new Properties()
    if (!versionPropsFile.exists()) {
        versionProps['VERSION_PATCH'] = "0"
        versionProps['VERSION_NUMBER'] = "0"
        versionProps['VERSION_BUILD'] = "-1" // I set it to minus one so the first build is 0 which isn't super important. 
        versionProps.store(versionPropsFile.newWriter(), null)
    }

    def runTasks = gradle.startParameter.taskNames
    if ('assembleRelease' in runTasks) {
        value = 1
    }

    def mVersionName = ""
    def mFileName = ""

    if (versionPropsFile.canRead()) {
        versionProps.load(new FileInputStream(versionPropsFile))

        versionProps['VERSION_PATCH'] = (versionProps['VERSION_PATCH'].toInteger() + value).toString()
        versionProps['VERSION_NUMBER'] = (versionProps['VERSION_NUMBER'].toInteger() + value).toString()
        versionProps['VERSION_BUILD'] = (versionProps['VERSION_BUILD'].toInteger() + 1).toString()

        versionProps.store(versionPropsFile.newWriter(), null)

        // 1: change major and minor version here
        mVersionName = "v1.0.${versionProps['VERSION_PATCH']}"
        // 2: change AppName for your app name
        mFileName = "AppName-${mVersionName}.apk"

        defaultConfig {
            minSdkVersion 21
            targetSdkVersion 27
            applicationId "com.example.appname" // 3: change to your package name
            versionCode versionProps['VERSION_NUMBER'].toInteger()
            versionName "${mVersionName} Build: ${versionProps['VERSION_BUILD']}"
        }

    } else {
        throw new FileNotFoundException("Could not read version.properties!")
    }

    if ('assembleRelease' in runTasks) {
        applicationVariants.all { variant ->
            variant.outputs.all { output ->
                if (output.outputFile != null && output.outputFile.name.endsWith('.apk')) {
                    outputFileName = mFileName
                }
            }
        }
    }

    task copyApkFiles(type: Copy){
        from 'build/outputs/apk/release'
        into '../apk'
        include mFileName
    }

    afterEvaluate {
        assembleRelease.doLast {
            tasks.copyApkFiles.execute()
        }
    }

    signingConfigs {
        ...
    }

    buildTypes {
        ...
    }
}