To get versionName and versionCode of current build of your application you should query Android’s package manager.

try {
    // Reference to Android's package manager
    PackageManager packageManager = this.getPackageManager();

    // Getting package info of this application
    PackageInfo info = packageManager.getPackageInfo(this.getPackageName(), 0);

    // Version code
    info.versionCode

    // Version name
    info.versionName

} catch (NameNotFoundException e) {
    // Handle the exception
}