good.cs

    /** Access to ```internal AndroidJavaObject(IntPtr jobject)``` */
    static readonly Fn<object[], AndroidJavaObject> ajoCreator = 
      PrivateConstructor.creator<AndroidJavaObject>();

    public static AndroidJavaObject cjoReturningNull(
      this AndroidJavaObject javaObject, string methodName, params object[] args
    ) {
      if (args == null) args = new object[1];
      var methodId = AndroidJNIHelper.GetMethodID<AndroidJavaObject>(
        javaObject.GetRawClass(), methodName, args, false
      );
      var jniArgArray = AndroidJNIHelper.CreateJNIArgArray(args);
      try {
        var returned = AndroidJNI.CallObjectMethod(
          javaObject.GetRawObject(), methodId, jniArgArray
        );
        if (returned == IntPtr.Zero) return null;
        else {
          try { return ajoCreator(new object[] {returned}); }
          finally { AndroidJNI.DeleteLocalRef(returned); }
        }
      }
      finally {
        AndroidJNIHelper.DeleteJNIArgArray(args, jniArgArray);
      }
    }