singning.properties configuration in your build.gradle so your credentials are safe(r)

build.gradle

File propFile = file('signing.properties');
if (propFile.exists()) {
    def Properties props = new Properties()
    props.load(new FileInputStream(propFile))

    if (props.containsKey('STORE_FILE') &&
            props.containsKey('STORE_PASSWORD') &&
            props.containsKey('KEY_ALIAS') &&
            props.containsKey('KEY_PASSWORD')) {

        android.signingConfigs.release.storeFile = file(props['STORE_FILE'])
        android.signingConfigs.release.storePassword = props['STORE_PASSWORD']
        android.signingConfigs.release.keyAlias = props['KEY_ALIAS']
        android.signingConfigs.release.keyPassword = props['KEY_PASSWORD']

    } else {
        android.buildTypes.release.signingConfig = null
    }

} else {
    android.buildTypes.release.signingConfig = null
}

/*
PLACE AT BOTTOM OF module.build.gradle
CREATE FILE signing.properties file

STORE_PASSWORD=yourpasswordincleartextetc
*/