(C++) How to show a dialog modally? or How to show a pop-up window?

 

How to show a dialog modally? is a QT FAQ one has to know the answer of for pop-up windows.

 

The answer is to call the 'exec' method of the dialog, as in the method below:

 

---

void DialogMain::onClickShow() {   boost::shared_ptr<DialogPopUp> f(new DialogPopUp);   f->exec(); //Show the pop-up modally }

 

For a full working example, you can:

• View the source of the Qt Creator project 'CppQtShowModal' below
• Download the Qt Creator project 'CppQtShowModal' (zip)

 

 

 

 

 

Project and source code

 

Operating system: Ubuntu 10.04 LTS Lucid Lynx

IDE: Qt Creator 2.0.0

Project type: Qt4 GUI Application

Compiler: G++ 4.4.1

Libraries used:

• Qt: version 4.7.0 (32 bit)

 

 

 

 

 

main.cpp

 

---

#include <QtGui/QApplication> #include "dialogmain.h" int main(int argc, char *argv[]) {   QApplication a(argc, argv);   DialogMain w;   w.show();   return a.exec(); }

 

 

 

 

 

dialogpopup.h

 

---

#ifndef DIALOGPOPUP_H #define DIALOGPOPUP_H #include <QDialog> namespace Ui {     class DialogPopUp; } class DialogPopUp : public QDialog {     Q_OBJECT public:     explicit DialogPopUp(QWidget *parent = 0);     ~DialogPopUp(); protected:     void changeEvent(QEvent *e); private:     Ui::DialogPopUp *ui; }; #endif // DIALOGPOPUP_H

 

 

 

 

 

dialogpopup.cpp

 

---

#include "dialogpopup.h" #include "ui_dialogpopup.h" DialogPopUp::DialogPopUp(QWidget *parent) :     QDialog(parent),     ui(new Ui::DialogPopUp) {     ui->setupUi(this); } DialogPopUp::~DialogPopUp() {     delete ui; } void DialogPopUp::changeEvent(QEvent *e) {     QDialog::changeEvent(e);     switch (e->type()) {     case QEvent::LanguageChange:         ui->retranslateUi(this);         break;     default:         break;     } }

 

 

 

 

 

dialogmain.h

 

---

#ifndef DIALOGMAIN_H #define DIALOGMAIN_H #include <QDialog> namespace Ui {     class DialogMain; } class DialogMain : public QDialog {     Q_OBJECT public:     explicit DialogMain(QWidget *parent = 0);     ~DialogMain(); protected:     void changeEvent(QEvent *e); private:     Ui::DialogMain *ui; private slots:     void onClickShow(); }; #endif // DIALOGMAIN_H

 

 

 

 

 

dialogmain.cpp

 

---

#include <boost/shared_ptr.hpp> #include "dialogpopup.h" #include "dialogmain.h" #include "ui_dialogmain.h" DialogMain::DialogMain(QWidget *parent) :     QDialog(parent),     ui(new Ui::DialogMain) {   ui->setupUi(this);   QObject::connect(ui->button_show,SIGNAL(clicked()),this,SLOT(onClickShow())); } DialogMain::~DialogMain() {   delete ui; } void DialogMain::changeEvent(QEvent *e) {   QDialog::changeEvent(e);   switch (e->type()) {   case QEvent::LanguageChange:     ui->retranslateUi(this);     break;   default:     break;   } } void DialogMain::onClickShow() {   boost::shared_ptr<DialogPopUp> f(new DialogPopUp);   this->hide(); //Hide the main window   f->exec(); //Show the pop-up modally   this->show(); //Show the main window again }