help with QAbstractNativeEventFilter

[alee]

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

#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

#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

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usbworker.cpp

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

#include "usbworker.h"

usbworker::usbworker()
{

}


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

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widget.h

#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

#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

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widget.cpp

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

#include "widget.h"
#include "ui_widget.h"


Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
}

Widget::~Widget()
{
    delete ui;
}

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main.cpp

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

#include "widget.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    
    return a.exec();
}

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i am using qt 5.1.0

[alee]

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

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

#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();
}

#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();
}

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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.