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

Kotlin example:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.act_signin)

    packageManager.getPackageInfo(packageName, PackageManager.GET_ACTIVITIES).apply {
        findViewById(R.id.text_version_name).text = versionName
        findViewById(R.id.text_version_code).text =
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) "$longVersionCode" else "$versionCode"
    }

    packageManager.getApplicationInfo(packageName, 0).apply{
        findViewById(R.id.text_build_date).text =
            SimpleDateFormat("yy-MM-dd hh:mm").format(java.io.File(sourceDir).lastModified())
    }
}

Don't thank :-)