QShowEvent example 1: visibility is a QShowEvent example that verifies that a widget is invisible in a dialog its constructor, but is visible in the showEvent member function.

Technical facts

Application type(s)

Desktop application

Operating system(s) or programming environment(s)

Lubuntu 13.04 (raring)

IDE(s):

Qt Creator 2.7.0

Project type:

GUI application

C++ standard:

C++98

Compiler(s):

G++ 4.7.3

Libraries used:

Qt: version 4.8.4 (32 bit)
STL: GNU ISO C++ Library, version 4.7.3

Qt project file: CppQShowEventExample1.pro


#-------------------------------------------------

#

# Project created by QtCreator 2013-05-04T15:13:50

#

#-------------------------------------------------



QT       += core gui



greaterThan(QT_MAJOR_VERSION, 4): QT += widgets



TARGET = CppQShowEventExample1

TEMPLATE = app





SOURCES += main.cpp\

        dialog.cpp



HEADERS  += dialog.h



FORMS    += dialog.ui

dialog.h


#ifndef DIALOG_H

#define DIALOG_H



#include <QDialog>

#include <QLabel>



namespace Ui {

  class Dialog;

}



class Dialog : public QDialog

{

  Q_OBJECT

  

public:

  explicit Dialog(QWidget *parent = 0);

  ~Dialog();



protected:

  void showEvent(QShowEvent *);

  

private:

  Ui::Dialog *ui;

  QLabel * const m_label;

};



#endif // DIALOG_H

dialog.cpp


#include "dialog.h"



#include <cassert>

#include <QDebug>

#include <QLabel>

#include <QShowEvent>

#include <QVBoxLayout>



#include "ui_dialog.h"



Dialog::Dialog(QWidget *parent) :

  QDialog(parent),

  ui(new Ui::Dialog),

  m_label(new QLabel("My label"))



{

  ui->setupUi(this);



  assert(!this->layout() && "No layout is present yet");

  this->setLayout(new QVBoxLayout);

  assert(this->layout() && "Vertical layout is present");



  this->layout()->addWidget(m_label);

  assert(!m_label->isVisible() && "Label is not visible yet");

  qDebug() << "End of constructor";

}



Dialog::~Dialog()

{

  delete ui;

}



void Dialog::showEvent(QShowEvent *)

{

  assert(m_label->isVisible() && "Label has been made visible now");

  qDebug() << "End of showEvent";

}

main.cpp


#include "dialog.h"

#include <QApplication>



int main(int argc, char *argv[])

{

  QApplication a(argc, argv);

  Dialog w;

  w.show();

  

  return a.exec();

}

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(C++) QShowEvent example 1: visibility

Technical facts

Qt project file: CppQShowEventExample1.pro

dialog.h

dialog.cpp

main.cpp