안드로이드 패키지 버젼 가져오는 방법

public static String getAppVersion(Context mContext) {
    String packageName = null;
    String appVersion = null;
    try {
        PackageInfo _package;
        packageName = mContext.getPackageName();
        _package = mContext.getPackageManager().getPackageInfo(packageName, 0);
        appVersion = _package.versionName;
    } catch (PackageManager.NameNotFoundException e1) {
        appVersion = "Unknown";
    }
    return appVersion;
}