Qt/C++ - Tutorial 063. Adding windows inside the main application window using QMdiArea

QMdiArea, QWidget, Qt

Many applications, like a photoshop, can open projects (images, texts, etc.) inside windows that open inside the main application window. Qt provides a similar function as QMdiArea . In an object of this class, you can place class objects inherited from the QWidget class, and accordingly the QWidget class. These objects will display as windows, only they will be located inside QMdiArea .

Let's see an example with a window inside the window.

Project structure

The following files are included in the project:

  • MdiWindow.pro - project profile, created by default;
  • main.cpp - the startup file of the program with the main function, created by default;
  • mainwindow.h - header file of the main application window;
  • mainwindow.cpp - the source code file for the main application window;
  • mainwindow.ui - form of the main application window;
  • icons.qrc - resource file, contains one icon.

Files MdiWindow.pro and main.cpp will not be considered, since they are created by default. The file icons.qrc contains one icon, which is visible on the toolbar of the main application window. This button is responsible for creating an additional application window and is added through the graphic designer. This Action is only needed to emit a signal to add new windows to QMdiArea .

Now let's move on to the essence of the project.

mainwindow.h

Header file of the main application window. Contains the declaration of the pointer to the QMdiArea object, as well as the declaration of the slot for adding new windows, which was created through the graphic designer.

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QMdiArea>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void on_actionAddWindow_triggered();

private:
    Ui::MainWindow *ui;
    QMdiArea * mdiArea;  // Area in which windows will be added
};

#endif // MAINWINDOW_H

mainwindow.cpp

The QMdiArea object is installed as the central widget for the main application window. Also, configure the scrollbars so that they appear only when necessary. In the add window add a QWidget object with an inscription. There is one point. If QWidget does not contain any content, it will open with a minimum size, even if you size it. And only when you try to move the window, this widget will take the size displayed.

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

#include <QGridLayout>
#include <QLabel>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    mdiArea = new QMdiArea(this);  // init QMdiArea
    // configure scrollbars
    mdiArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAsNeeded);
    mdiArea->setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
    // Set Mdi Area as the central widget
    setCentralWidget(mdiArea);
}

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

void MainWindow::on_actionAddWindow_triggered()
{
    // Create a widget that will be a window
    QWidget *widget = new QWidget(mdiArea);
    // Adding layout to it
    QGridLayout *gridLayout = new QGridLayout(widget);
    widget->setLayout(gridLayout);
    // Adding an label to the widget
    QLabel *label = new QLabel("Hello, I am sub window!!!", widget);
    gridLayout->addWidget(label);

    // Adding a widget as a sub window in the Mdi Area
    mdiArea->addSubWindow(widget);
    // Set the window title
    widget->setWindowTitle("Sub Window");
    // And show the widget
    widget->show();
}

Download the project with an example QMdiArea

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TT
June 13, 2019, 7:01 p.m.
Taimoor Tanweer

C++ - Test 001. The first program and data types

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TT
June 13, 2019, 6:51 p.m.
Taimoor Tanweer

C++ - Test 002. Constants

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ВМ
June 13, 2019, 12:30 p.m.
Ваня Мороз

C++ - Test 001. The first program and data types

  • Result:100points,
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Last comments
МБ
June 20, 2019, 6:23 p.m.
Михаил Булатов

А если мне нужно сделать конект из дочернего qml?Сигнал работает только из main.qml
i
June 17, 2019, 6:10 a.m.
ingenfly

Только по осям xAxis2, уAxis2 значения начинаются с 0. Почему-то xAxis2 и xAxis не синхронизированы по данным. Ну и QCustomPlot последний.
June 16, 2019, 8:21 p.m.
Евгений Легоцкой

Добрый день. Ну точно также добавляете ту же самую информацию на ось xAxis2, только добавляете другое форматирование customPlot->xAxis2->setDateTimeFormat("hh:mm"); если я ...
EF
June 14, 2019, 1:56 p.m.
Egor Fomin

Спасибо за ваш ответ, у меня получилось реализовать это. Тем не менее появилась другая проблема, поэтому опять надеюсь на вашу помощь. Скажем, я уже выставил точки и они соеденены. Когда я нач...
d
June 13, 2019, 2:47 p.m.
damix

Можно классу, который описывает точку, добавить сигнал, который подавать (emit), когда точка перемещается (переопределить mouseMoveEvent или mouseReleaseEvent). Так вот эти сигналы у каждой из...
Now discuss on the forum
June 20, 2019, 9:30 a.m.
IscanderChe

Вернулся к этой задачке только-только, поэтому и не ответил ничего раньше.Как переопределить mouseReleaseEvent(QMouseEvent* event) у QTableView, если QTableView задан в ui? Или задавать QTabl...
I
June 19, 2019, 1:41 p.m.
Intruder

Всем добрый день. При разборе XML файла наткнулся на тег вот такого плана: <TagName attribute1="value1" attribute2="value2" /> При попытке проверить на наличие такого элеме...
June 19, 2019, 12:55 p.m.
Михаиллл

Скажите пожалуйста, как его в таком случае перемещать и удалять?
June 18, 2019, 7:50 p.m.
Дмитрий

Большое спасибо! SDK заработал.К сожалению удалось продвинутся только на один шаг. При сборке чистого проекта NDK выдаёт следующие ошибки C:\Android\ndk-bundle/toolchains/arm-linux-andr...
June 18, 2019, 4:59 p.m.
Михаиллл

Добрый день.В этом учебнике представлен код INSTALLED_APPS = ( ... 'rest_framework', 'snippets.apps.SnippetsConfig',) На строчке 'snippets.apps.SnippetsConf...
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