code: public static String generateUserAgent(Context context) {
          StringBuilder ua = new StringBuilder("api-client/");
          ua.append(VERSION);
  
          String packageName = context.getApplicationContext().getPackageName();
  
          ua.append(" ");
          ua.append(packageName);
  
          PackageInfo pi = null;
          try {
              pi = context.getPackageManager().getPackageInfo(packageName, 0);
          } catch (PackageManager.NameNotFoundException e) {
              e.printStackTrace();
          }
          if (pi != null) {
              ua.append("/");
              ua.append(pi.versionName);
              ua.append("(");
              ua.append(pi.versionCode);
              ua.append(")");
          }
          ua.append(" Android/");
          ua.append(Build.VERSION.SDK_INT);
  
          try {
              ua.append(" ");
              ua.append(Build.PRODUCT);
          } catch (Exception e) {
              e.printStackTrace();
          }
  
          try {
              ua.append(" ");
              ua.append(Build.MANUFACTURER);
          } catch (Exception e) {
              e.printStackTrace();
          }
  
          try {
              ua.append(" ");
              ua.append(Build.MODEL);
          } catch (Exception e) {
              e.printStackTrace();
          }
  
          return ua.toString();
      }
docs: build the default User-Agent
  
  @param context
  @return