#include <QtGui/QApplication>#include <QtGui/QMainWindow>#include <QtGui/QDialog>#include <QtGui/QPushButton>class MainWindow : public QMainWindow{ Q_OBJECTpublic: MainWindow() { QPushButton *button = new QPushButton( "Show dialog", this ); connect( button, SIGNAL(clicked()), SLOT(onShowDialog()) ); }protected slots: void MainWindow::onShowDialog() { QDialog *pDialog = new QDialog( this ); pDialog->setWindowModality( Qt::WindowModal ); pDialog->show(); pDialog->activateWindow(); }};int main(int argc, char *argv[]){ QApplication a(argc, argv); MainWindow w; w.show(); return a.exec();}