Versioning Android Apps - Simple schema - https://medium.com/dipien/versioning-android-apps-d6ec171cfd82

build.gradle

apply plugin: 'com.android.application'

ext.versionMajor = 1
ext.versionMinor = 2
ext.versionPatch = 3
ext.versionClassifier = null
ext.isSnapshot = true

android {
	defaultConfig {
		versionCode generateVersionCode() // 010203
		versionName generateVersionName() // 1.2.3-SNAPSHOT
	}
}

private Integer generateVersionCode() {
	return ext.versionMajor * 10000 + ext.versionMinor * 100 + ext.versionPatch
}

private String generateVersionName() {
	String versionName = "${ext.versionMajor}.${ext.versionMinor}.${ext.versionPatch}"
	if (ext.versionClassifier == null && ext.isSnapshot) {
		ext.versionClassifier = "SNAPSHOT"
	}

	if (ext.versionClassifier != null) {
		versionName += "-" + ext.versionClassifier
	}
	return versionName;
}