How to get the build/version number of your Android application?

Question

I need to figure out how to get or make a build number for my Android application. I need the build number to display in the UI.

Do I have to do something with

Answer 1

Use BuildConfig class

String versionName = BuildConfig.VERSION_NAME;
int versionCode = BuildConfig.VERSION_CODE;

build.gradle(app)

 defaultConfig {
    applicationId "com.myapp"
    minSdkVersion 19
    targetSdkVersion 27
    versionCode 17
    versionName "1.0"
   }