QSplitterWithMDI.CPP

#include <QApplication>
#include <QMainWindow>
#include <QMenuBar>
#include <QMdiArea>
#include <QMdiSubWindow>
#include <QTextEdit>
#include <QVBoxLayout>
#include <QPushButton>
#include <QSignalMapper>
#include <QMainWindow>
#include <QToolBar>
#include <QAction>
#include <QTextEdit>
#include <QSplitter>
#include <QToolBar>
#include <QMessageBox>
#include <QTabBar>

class WidgetContainer: public QSplitter{

public:
    WidgetContainer(QWidget *parent): QSplitter(parent){
            // Create a vertical layout for the main window
             QVBoxLayout mainLayout(this);
             this->setOrientation(Qt::Horizontal);
            // Create widgets to be added to the splitter
            QTextEdit *textEdit1 = new QTextEdit;
            QTextEdit *textEdit2 = new QTextEdit;
            // Add widgets to the splitter
            addWidget(textEdit1);
            addWidget(textEdit2);
            // Create a button for toggling collapsibility
            QPushButton toggleButton("Toggle Collapsibility");

            // Connect the button's clicked signal to a slot that toggles the collapsibility
            QObject::connect(&toggleButton, &QPushButton::clicked, [this]() {
                // Toggle the collapsibility of the second handle
                setCollapsible(1, !this->isCollapsible(1));
            });
            setSizes(QList<int>() << 100 << 600);
    }
};

class MainWindow : public QMainWindow {
  ///  Q_OBJECT

    QTabBar* tabBar;
    QMdiArea* mdiArea;
    QVBoxLayout *centralLayout = new QVBoxLayout();

    void updateTabBar() {
            // Clear existing tabs
            tabBar->removeTab(0);


            // Add tabs for each MDI child window
            QList<QMdiSubWindow *> subWindows = mdiArea->subWindowList();
            for (QMdiSubWindow *subWindow : subWindows) {
                tabBar->addTab(subWindow->windowTitle());
            }
    }

    void closeTab(int index) {
            QMdiSubWindow *subWindow = mdiArea->subWindowList().at(index);
            if (subWindow) {
                subWindow->close();
            }
    }

    void createMdiChild(const QString &title) {
            QTextEdit *textEdit = new QTextEdit;
            QMdiSubWindow *subWindow = mdiArea->addSubWindow(textEdit);
            subWindow->setWindowTitle(title);
            subWindow->show();

            // Update the tab bar
            updateTabBar();
    }

    void addMdiChild() {
            static int childNumber = 2;
            createMdiChild("Document " + QString::number(childNumber));
            ++childNumber;
    }


    void createInstanceOfCenterLayout(){
            centralLayout = new QVBoxLayout();
            tabBar = new QTabBar(this);
            connect(tabBar, &QTabBar::tabCloseRequested, this, &MainWindow::closeTab);
            mdiArea = new QMdiArea(this);
            connect(mdiArea, &QMdiArea::subWindowActivated, this, &MainWindow::updateTabBar);
    }

    void configureLayout(){
            // Add the tab bar and MDI area to the central layout
            centralLayout->addWidget(tabBar);
            centralLayout->addWidget(mdiArea);

            // Create a central widget to hold the layout
            QWidget *centralWidget = new QWidget(this);
            centralWidget->setLayout(centralLayout);
            setCentralWidget(centralWidget);
    }

    void addAction(){
            // Create an "Add MDI Child" action
            QAction *addAction = new QAction("Add MDI Child", this);
            connect(addAction, &QAction::triggered, this, &MainWindow::addMdiChild);

            // Add the action to the toolbar
            QToolBar *navToolBar = addToolBar("Navigation");
            navToolBar->addAction(addAction);
            // Create actions for managing MDI child windows
            QAction *newAction = new QAction("New", this);
            QAction *cascadeAction = new QAction("Cascade", this);
            QAction *tileAction = new QAction("Tile", this);

            // Connect actions to slots
            connect(newAction, &QAction::triggered, this, &MainWindow::createNewChild);
            connect(cascadeAction, &QAction::triggered, mdiArea, &QMdiArea::cascadeSubWindows);
            connect(tileAction, &QAction::triggered, mdiArea, &QMdiArea::tileSubWindows);

            // Add actions to the toolbar
           navToolBar->addAction(newAction);
           navToolBar->addAction(cascadeAction);
           navToolBar->addAction(tileAction);

    }

public:
    MainWindow(QWidget *parent = nullptr) : QMainWindow(parent) {
            createInstanceOfCenterLayout();
            configureLayout();
            addAction();
    }

private slots:
    void createNewChild() {
        // Create a new QTextEdit as an MDI child
        auto *window = new WidgetContainer(this);
        QMdiSubWindow *subWindow = mdiArea->addSubWindow(window);

        // Set window properties
        subWindow->setAttribute(Qt::WA_DeleteOnClose);
        subWindow->setWindowTitle("Document");
        subWindow->show();
    }

private:

};

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);

    MainWindow mainWindow;
    mainWindow.setWindowTitle("test of MDI");
    mainWindow.show();

    return app.exec();
}