QWidget::create: Failed to create window () Why my application crash?

Hi,

QWidget::create: Failed to create window () Why my application crash?

DialogByButton.pro

Code:

---

SOURCES += \
    main.cpp \
    mainwindow.cpp \
    dialog.cpp
 
HEADERS += \
    mainwindow.h \
    dialog.h

---

main.cpp

Code:

---

#include <QApplication>
#include "mainwindow.h"
 
int main (int argc, char *argv[]) {
    QApplication app(argc, argv);
 
    MainWindow window;
    window.show();
 
    return app.exec();
}

---

mainwindow.h

Code:

---

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <QtGui>
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
 
signals:
    //void sendName(QString name);
 
private slots:
    //void callDialog();
 
private:
    QLineEdit *leName;
};
 
#endif // MAINWINDOW_H

---

mainwindow.cpp

Code:

---

#include "mainwindow.h"
//#include "dialog.h"
//#include <QWidget>
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)
{
    // Controls
    //QLabel *lblName = new QLabel(tr("Enter your name:"));
    leName = new QLineEdit;
    //QPushButton *btnCallDialog = new QPushButton(tr("Call Dialog"));
 
//    // Layout
//    QGridLayout *mainLayout = new QGridLayout(this);
//    mainLayout->addWidget(lblName, 0, 0);
//    mainLayout->addWidget(leName, 0, 1);
//    mainLayout->addWidget(btnCallDialog, 1, 0, 1, 2);
 
//    // Set center widget
//    QWidget *widget = new QWidget;
//    widget->setLayout(mainLayout);
//    this->setCentralWidget(widget);
 
//    //connect(btnCallDialog, SIGNAL(clicked()), this, SLOT(callDialog()));
}
 
//void MainWindow::callDialog() {
//    QDialog *dialog = new QDialog(this);
//    connect(this, SIGNAL(sendName(QString)), dialog, SLOT(showName(QString)));
//    emit sendName(leName->text());
//    dialog->show();
//}

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Sorry, I solved this problem. I click "Clean".