1.窗体居中显示

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

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    w.move((QApplication::desktop()->width()-w.width())/2,
           (QApplication::desktop()->height()-w.height())/2);
    return a.exec();
}