QT Slots and signals, showing 2nd form/window

Question

I have a QT application and I'm trying to have a button in one of my windows open another window.

The way I have done my window objects so far in the main is like this:

Website control;
control.show();

This displays my first window fine and if I declare my other window in a similar way that also displays at runtime, although this is not what I want

Then in a separate header file:

class Website: public QWidget, public Ui::Website
{
public:
Website();
}

Then in the corresponding Cpp file I have:

Website::Website()
{
setupUi(this);
}

Now all this works and have added a custom slot so that when I click a button it triggers a slot in my other cpp file. The issue is I'm not sure how to show my other window as I declare them in my main so can't access them to do .show()?

Any help would be appreciated, I'm fairly new to C++ and QT

Answer 1

It's not clear to me what you want to do. But i might understand your struggle as I had one myself the first time approaching this framework.

So let's say you have a MainWindow class that controls the main Window view. Than you want to create a second window controlled by Website class.

You then want to connect the two classes so that when you click a button on the Website window something happens in the MainWindow.

I made a simple example for you that is also on GitHub :

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "website.h"

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

public slots:
    void changeText();

private slots:
    void on_openButton_clicked();

private:
    Ui::MainWindow *ui;

    //You want to keep a pointer to a new Website window
    Website* webWindow;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::changeText()
{
    ui->text->setText("New Text");
    delete webWindow;
}

void MainWindow::on_openButton_clicked()
{
    webWindow = new Website();
    QObject::connect(webWindow, SIGNAL(buttonPressed()), this, SLOT(changeText()));
    webWindow->show();
}

website.h

#ifndef WEBSITE_H
#define WEBSITE_H

#include <QDialog>

namespace Ui {
class Website;
}

class Website : public QDialog
{
    Q_OBJECT

public:
    explicit Website(QWidget *parent = 0);
    ~Website();

signals:
    void buttonPressed();

private slots:
    void on_changeButton_clicked();

private:
    Ui::Website *ui;
};

#endif // WEBSITE_H

website.cpp

#include "website.h"
#include "ui_website.h"

Website::Website(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Website)
{
    ui->setupUi(this);
}

Website::~Website()
{
    delete ui;
}

void Website::on_changeButton_clicked()
{
    emit buttonPressed();
}

Project composed:

SOURCES += main.cpp\
        mainwindow.cpp \
    website.cpp

HEADERS  += mainwindow.h \
    website.h

FORMS    += mainwindow.ui \
    website.ui

Consider the Uis to be composed:

• Main Window: a label called "text" and a button called "openButton"
• Website Window: a button called "changeButton"

So the keypoints are the connections between signals and slots and the management of windows pointers or references.