warning: invalid use of incomplete type 'class QEvent'

[focusdoit]

I got this warning when I compile the following code:
//MainWindow.h

#include <QPushButton>
#include "mywidget.h"
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
protected:
    bool eventFilter(QObject *obj, QEvent *e);
private:
    QPushButton *button;
 
};

#include <QPushButton>
#include "mywidget.h"

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
protected:
    bool eventFilter(QObject *obj, QEvent *e);
private:
    QPushButton *button;

};

To copy to clipboard, switch view to plain text mode 

//MainWindow.cpp

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    button = new QPushButton;
    this->setCentralWidget(button);
    button->installEventFilter(button ); 
}
 
MainWindow::~MainWindow()
{
}
 
bool MainWindow::eventFilter(QObject *obj,QEvent *e)
{
    if (obj == button)       
    {
        if (e->type() == QEvent::MouseButtonPress)   // this is the statement warning happened.
        {
            QMouseEvent *event = static_cast<QMouseEvent*> (e);
            button->setText(QString("Press: %1, %2").arg(QString::number(event->x()), QString::number(event->y())));
            return true;
        }
     ...
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    button = new QPushButton;
    this->setCentralWidget(button);
    button->installEventFilter(button ); 
}

MainWindow::~MainWindow()
{
}

bool MainWindow::eventFilter(QObject *obj,QEvent *e)
{
    if (obj == button)       
    {
        if (e->type() == QEvent::MouseButtonPress)   // this is the statement warning happened.
        {
            QMouseEvent *event = static_cast<QMouseEvent*> (e);
            button->setText(QString("Press: %1, %2").arg(QString::number(event->x()), QString::number(event->y())));
            return true;
        }
     ...
}

To copy to clipboard, switch view to plain text mode 

Anybody can help me to find the reason?

[anda_skoa]

That kind of error indicates a missing include.
In your case the include for QMouseEvent.

Cheers,
_