How to call a static method of java from c++ side?

[stereoMatching]

simpleJNI.hpp



#include <QObject>

class simpleJNI : public QObject
{
Q_OBJECT
public:
explicit simpleJNI(QObject *parent = nullptr);

Q_INVOKABLE QString printHelloWorld();

};



simpleJNI.cpp



#include "simpleJNI.hpp"

#include <QtAndroidExtras/QAndroidJniObject>

simpleJNI::simpleJNI(QObject *parent) :
QObject(parent)
{
}


QString simpleJNI::printHelloWorld()
{
QAndroidJniObject str = QAndroidJniObject::callStaticObjectMethod("adv/appBucksAdv",
"getString",
"(V)Ljava/lang/String;"
);

return str.toString();
}



appBucksAdv.java



//package adv;

import org.qtproject.qt5.android.bindings.QtApplication;
import org.qtproject.qt5.android.bindings.QtActivity;
//import android.content.Context;

public class appBucksAdv extends QtActivity
{
public static String getString()
{
return "hello world";
}
}



main.qml



import QtQuick 2.2
import QtQuick.Controls 1.1

Rectangle {
width: 100
height: 62

color: "red"

Text{
id: text
height: 30
width: parent.width
anchors.centerIn: parent
}

MouseArea{
anchors.fill: parent

onClicked: {
text.text = text.text + simpleJNI.printHelloWorld() + "\n"
}
}
}


But the program do not print “helloWorld\n”

message :
W/dalvikvm( 6727): Bogus method descriptor: (V)Ljava/lang/String;

Layout of the project https://github.com/stereomatchingkiss/blogCodes2/tree/master/androidTest

Added after 28 minutes:

If I change the signature of the function to


public static String printHelloWorld(int a)
{
return "hello world";
}

and simpleJNI.cpp to



QString simpleJNI::printHelloWorld()
{
QAndroidJniObject str = QAndroidJniObject::callStaticObjectMethod("adv/appBucksAdv",
"printHelloWorld",
//change (V) to (I)
"(I)Ljava/lang/String;",
23);

return str.toString();
}



The codes work