Gradle function to replace a placeholder string in AndroidManifest.xml with productFlavor package name

android_replace_in_manifest.gradle

replaceInManifest = {variant, fromString, toString ->
    def flavor = variant.productFlavors.get(0)
    def buildtype = variant.buildType
    def manifestFile = "$buildDir/manifests/${flavor.name}/${buildtype.name}/AndroidManifest.xml"
    def updatedContent = new File(manifestFile).getText('UTF-8').replaceAll(fromString, toString)
    new File(manifestFile).write(updatedContent, 'UTF-8')
}

flavor_packagename_replace.gradle

applicationVariants.all { variant ->
    def flavor = variant.productFlavors.get(0)
    def buildType = variant.buildType
    variant.processManifest.doLast {
        println '################# Adding Package Names to Manifest #######################'
        replaceInManifest(variant,
            'PACKAGE_NAME',
            [flavor.packageName, buildType.packageNameSuffix].findAll().join()) // ignores null
    }
}