How to call function after window is shown?

Question

Using Qt I create a QMainWindow and want to call a function AFTER the windows is shown. When I call the function in the constructor the fun

Answer 1

Follow Reza Ebrahimi's example, but keep this in mind:

Do not omit the 5th parameter of connect() function which specifies the connection type; make sure it to be QueuedConnection.

I.E.,

connect(this, SIGNAL(window_loaded), this, SLOT(your_function()), Qt::ConnectionType(Qt::QueuedConnection | Qt::UniqueConnection));

I believe that you'd achieve what you need if you do it this way.

• There are several types in signal-slot connections: AutoConnection, DirectConnection, QueuedConnection, BlockingQueuedConnection (+ optional UniqueConnection). Read the manual for details. :)

Answer 2

The best solution for me is count once paint event:

.H

public:
void paintEvent(QPaintEvent *event);

.CPP

#include "qpainter.h"
#include <QMessageBox> // example

int contPaintEvent= 0;

void Form2::paintEvent(QPaintEvent* event)
{
  if (contPaintEvent ==0 )
  {
  QPainter painter(this); 
  QMessageBox::information(this, "title", "1 event paint"); // example
  // actions
  contPaintEvent++;
  }
}

Answer 3

If you want to do something while the widget is made visible, you can override QWidget::showEvent like this:

class YourWidget : public QWidget { ...

void YourWidget::showEvent( QShowEvent* event ) {
    QWidget::showEvent( event );
    //your code here
}