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Multiple signals handling in one slot



  • Hi, dear Qt community! I am new to Qt development, few days ago started to learn this library.
    I want to handle the pushButtons onClicked signals from QML front-end in C++ back-end., am i using the right approach for this task? or i should use another more proper way? Please give any advice..

    here is my simple code (Qt Quick project):

    backend.h

    #ifndef BACKEND_H
    #define BACKEND_H
    
    #include <QObject>
    #include <QMessageBox>
    
    class BackEnd : public QObject
    {
        Q_OBJECT
    public:
        explicit BackEnd(QObject *parent = nullptr);
    
    signals:
    
    public slots:
        void qml_Events_Handler(QString Id);
    
    };
    
    #endif // BACKEND_H
    

    backend.cpp

    #include "backend.h"
    
    
    BackEnd::BackEnd(QObject *parent) : QObject(parent)
    {
    
    }
    
    void BackEnd::qml_Events_Handler(QString Control_ID)
    {
        if(Control_ID=="button")
        {
           QMessageBox msgBox;
           msgBox.setText("Hello QML.");
           msgBox.exec();
        }
    
        if(Control_ID=="button1")
        {
            QMessageBox::warning(nullptr,tr("Тест"),"This is a text",QMessageBox::Ok);
        }
    
        Control_ID.clear();
    
    }
    

    main.cpp

    #include <QApplication>
    #include <QQmlApplicationEngine>
    #include <QQmlContext>
    #include "backend.h"
    
    
    int main(int argc, char *argv[])
    {
        QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    
        QApplication app(argc, argv);
    
        QQmlApplicationEngine engine;
    
        BackEnd backend;
        engine.rootContext()->setContextProperty("backend", &backend);
    
        const QUrl url(QStringLiteral("qrc:/main.qml"));
        QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                         &app, [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl)
                QCoreApplication::exit(-1);
        }, Qt::QueuedConnection);
        engine.load(url);
    
        return app.exec();
    }
    

    main.qml

    import QtQuick 2.14
    import QtQuick.Controls 2.12
    import QtQuick.Window 2.14
    
    Window {
        id: mainWindow
        visible: true
        width: 360
        height: 360
        flags: Qt.FramelessWindowHint | Qt.Window
        color: "transparent"
    
        Rectangle {
            color: "#191919"
            anchors.fill: parent
            anchors.margins: 10
            radius: 30
            anchors.leftMargin: 10
            anchors.bottomMargin: 242
            opacity: 1
            clip: true
            anchors.rightMargin: 10
            anchors.topMargin: 20
    
            MouseArea {
    
                anchors.fill: parent;
                   property variant clickPos: "1,1"
                opacity: 1
    
                onPressed: {
                    clickPos = Qt.point(mouse.x,mouse.y)
                   }
    
                   onPositionChanged: {
                       var delta = Qt.point(mouse.x-clickPos.x, mouse.y-clickPos.y)
                       var new_x = mainWindow.x + delta.x
                       var new_y = mainWindow.y + delta.y
                       if (new_y <= 0)
                           mainWindow.visibility = Window.Maximized
                       else
                       {
                           if (mainWindow.visibility === Window.Maximized)
                               mainWindow.visibility = Window.Windowed
                           mainWindow.x = new_x
                           mainWindow.y = new_y
                       }
                   }
    
                   Button {
                       id: button
                       x: 174
                       y: 29
                       text: qsTr("Click Me")
                       highlighted: true
                       onClicked: backend.qml_Events_Handler("button")
                   }
             }
        }
    
        Rectangle {
            color: "#191919"
            anchors.fill: parent
            anchors.margins: 10
            radius: 30
            rotation: 45
            anchors.leftMargin: -15
            anchors.bottomMargin: 126
            opacity: 1
            clip: true
            anchors.rightMargin: 35
            anchors.topMargin: 136
    
            MouseArea {
    
                anchors.fill: parent;
                   property variant clickPos: "1,1"
                opacity: 1
    
                onPressed: {
                    clickPos = Qt.point(mouse.x,mouse.y)
                   }
    
                   onPositionChanged: {
                       var delta = Qt.point(mouse.x-clickPos.x, mouse.y-clickPos.y)
                       var new_x = mainWindow.x + delta.x
                       var new_y = mainWindow.y + delta.y
                       if (new_y <= 0)
                           mainWindow.visibility = Window.Maximized
                       else
                       {
                           if (mainWindow.visibility === Window.Maximized)
                               mainWindow.visibility = Window.Windowed
                           mainWindow.x = new_x
                           mainWindow.y = new_y
                       }
                   }
    
                   Button {
                       id: button1
                       x: 149
                       y: 28
                       text: qsTr("Close")
                       highlighted: true
                       clip: false
                       onClicked:
                       {
                           backend.qml_Events_Handler("button1")
                           mainWindow.close()
                       }
    
                   }
             }
        }
    
    }
    


  • Am I using right technique to pass control ID as a string from QML to c++?


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