help with QAbstractNativeEventFilter

hi,

i am trying to catch native events on the windows platform, to communicate with an hid usb device.... i have successfully done so using the nativeEvent method in QWidget....now i am trying to create a generic class that can be added to any QWidget or QMainWindow.

for this pupose i am trying to derive a class from QAbstractNativeEventFilter .... Override the virtual nativeEventFilter and instantiate this class in the QWidget of my choice....yet i am unable to recieve any events so far.....

i am new to qt and havent had much experience using abstract classes.....i am attaching a sample below....using this example the code compiles and the widget window appears but the nativeeventfilter method is not called. any help would be highly appreciated.....

usbworker.h

Code:

---

#ifndef USBWORKER_H
#define USBWORKER_H
 
#include <QAbstractNativeEventFilter>
 
class usbworker : public QAbstractNativeEventFilter
{
public:
    usbworker();
    virtual bool nativeEventFilter(const QByteArray &eventType, void *message, long *result);
 
};
 
#endif // USBWORKER_H

---

usbworker.cpp

Code:

---

#include "usbworker.h"
 
usbworker::usbworker()
{
 
}
 
 
bool usbworker::nativeEventFilter(const QByteArray &eventType, void *message, long *result)
Q_DECL_OVERRIDE
{
    qDebug("i came here");
    return false;
}

---

widget.h

Code:

---

#ifndef WIDGET_H
#define WIDGET_H
 
#include <QWidget>
#include <usbworker.h>
 
namespace Ui {
class Widget;
}
 
class Widget : public QWidget
{
    Q_OBJECT
 
public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();
    usbworker uw;
 
private:
    Ui::Widget *ui;
};
 
#endif // WIDGET_H

---

widget.cpp

Code:

---

#include "widget.h"
#include "ui_widget.h"
 
 
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
}
 
Widget::~Widget()
{
    delete ui;
}

---

main.cpp

Code:

---

#include "widget.h"
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
 
    return a.exec();
}

---

i am using qt 5.1.0

i have sorted how to do this.....:D

it was said in the documentation that, the filter needs to installed on the application object.....i tried finding what that meant and found no results, at least none that i could understand....then i started browsing through the documention of QAbstractEventDispatcher and their i found an indirect hint. i followed up on it and, viola!!! it worked....

the changes needed to be made to main.cpp below is the reivsed code. i needed to installNativeEventFilter on the application instance in the main file

Code:

---

#include "widget.h"
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    a.installNativeEventFilter(&w.uw); //this installs the instance uw of the usbworker inside the widget w, on the application instance a.
    w.show();
 
    return a.exec();
}

---

i have further modified my usbworkerclass to inherit from QObject and QAbstractNativeEventFilter. since the later is an abstract class(an interface) it is ok to inherit multiple.(correct me if i am wrong).....

it would be great if the documentation of the abstract class be made a bit clearer....or probably its just me who did not understand it.