Custom apk name

build.gradle

buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.config
            applicationVariants.all { variant ->
                variant.outputs.each { output ->
                    project.ext { appName = 'whpicking' }
                    def formattedDate =  "-" + variant.versionName + "_" + variant.versionCode + "-" + new Date().format('yyyyMMddHHmmss')
                    def newName = output.outputFile.name
                    newName = newName.replace("app-", "$project.ext.appName-")
                    newName = newName.replace("-release", "-release" + formattedDate)
                    output.outputFile = new File(output.outputFile.parent, newName)
                }
            }
        }
    }