Print Preview in Qt

I want to preview a page or want to have print preview. A preview window is opening but the contents of qt window is not comming in it. My code to print preview is as follows:

void User::on_actionprintPreview_triggered()
{
    QPrinter printer(QPrinter::HighResolution);
    QPrintPreviewDialog preview(&printer, this);
    connect(&preview, SIGNAL(paintRequested(QPrinter *)),
            this, SLOT(print(QPrinter *)));
    preview.exec();
}

How can I get the content of the qt window in it. Does I am doing something wrong. Please help me out to solve this.