QAndroidJniObject::callstaticobjectmethod return empty string

[JRobles]

Hello I have this code:

QAndroidJniObject string = QAndroidJniObject::callStaticObjectMethod<jstring>("com/app/utils/MyParams", "getEmpty");
qDebug() << "stringContent:" << string.toString();

QAndroidJniObject jniParam = QAndroidJniObject::fromString("name" );
 QAndroidJniObject jniParamValue =  QAndroidJniObject::callStaticObjectMethod(
                            "com/app/utils/MyParams" // class name
                            , "getStaticParam" // method name
                            , "Ljava/lang/String;" // signature
                            , jniParam.object<jstring>() );

qDebug() << "param:" << jniParam.toString();

on java:

 public static String getStaticParam(String param){
        String realParamName = "Param_ " + param;        
        return realParamName;
    }


public static String getEmpty(){
    String realPath = "EMPTY";
    return realPath;
}

When I call the 'getEmpty' method it works ok, console prints 'stringContent:EMTPY' but when I call the second method it always return an empty string, I don't know why.

I read that maybe I need to add the return type to the function (QAndroidJniObject::callStaticObjectMethod<jstring>) but doing that gives me an error on QT.

"no matching function for call to 'callStaticObjectMethod'"

what Im missing?