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Calling qml on mainwindow

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  • V Offline
    V Offline
    vibolvireak
    wrote on last edited by
    #1

    Hello. i try to call qml file with mainwindow class. here my code

    mainwindow.h

    #ifndef MAINWINDOW_H
    #define MAINWINDOW_H
    
    
    #include <QMainWindow>
    
    class MainWindow : public QMainWindow {
        Q_OBJECT
    public:
        explicit MainWindow(QWidget *parent = 0);
    
    
    private:
    
    public slots:
    
    };
    
    
    #endif // MAINWINDOW_H
    
    

    mainwindow.cpp

    #include "mainwindow.h"
    #include "qqmlapplicationengine.h"
    
    MainWindow::MainWindow(QWidget *parent) :
        QMainWindow(parent)
    {
        QQmlApplicationEngine engine;
        engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    }
    
    

    main.cpp

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

    I can loading window normal but the window is not from qml it look like and empty window.

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    0
    • p3c0P Offline
      p3c0P Offline
      p3c0
      Moderators
      wrote on last edited by
      #2

      Hi,
      IMO, if you are trying to embed a QML file then a better option would be to use QQuickWidget

      157

      1 Reply Last reply
      1
      • V Offline
        V Offline
        vibolvireak
        wrote on last edited by
        #3

        Hello, i'm thank for your response.

        After i use QQuickWidgets, When i run the project it seen to launch 2 window at the same time.

        I was create a qml project. and i see in my resource file has 2 qml file which name
        main.qml, mainform.ui.qml.
        Note***

        1. if i use qqmlapplicaitonengine i will see the form suddenly close when it run
        2. if i use qquickview the window will launch normally but.. the message say
        QML debugging is enabled. Only use this in a safe environment.
        QQuickView does not support using windows as a root item. 
        
        If you wish to create your root window from QML, consider using QQmlApplicationEngine instead. 
        
        1. if i use qquickwidget it will see the 2 window main.qml, mainwindow.ui.qml will launch at the same time.
        1 Reply Last reply
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        • jsulmJ Offline
          jsulmJ Offline
          jsulm
          Lifetime Qt Champion
          wrote on last edited by
          #4

          Well, if you have a MainWindow AND a QML window then you get two windows. Do you really need this MainWindow? If not remove it and only use main.qml via QQmlApplicationEngine instead.

          https://forum.qt.io/topic/113070/qt-code-of-conduct

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          0
          • V Offline
            V Offline
            vibolvireak
            wrote on last edited by
            #5

            I'm sorry @jsulm i'm not i'm not good at c++ but i'm understand what your mean. Because i sperate a class name mainwindow and call it to main.cpp and i call the qml file inslude a class on file mainwindow.cpp. So the main problem is if i use qqmlapplicationengine it will suddenly close my window when it start ... I mean it will open and close at the same time..

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            • jsulmJ Offline
              jsulmJ Offline
              jsulm
              Lifetime Qt Champion
              wrote on last edited by
              #6

              Here you can see an example: http://doc.qt.io/qt-5/qqmlapplicationengine.html

              #include <QGuiApplication>
              #include <QQmlApplicationEngine>
              
              int main(int argc, char *argv[])
              {
                  QGuiApplication app(argc, argv);
                  QQmlApplicationEngine engine("main.qml");
                  return app.exec();
              }
              

              Are you doing it now this way, or do you still have MainWindow + main.qml?

              https://forum.qt.io/topic/113070/qt-code-of-conduct

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              • V Offline
                V Offline
                vibolvireak
                wrote on last edited by
                #7

                the default is like this. But i just think i want to include a mainwindow class because it easy to connect with a slot and signal. As i see in qt application there should be main.cpp, mainwindow.cpp, mainwindow.h and also mainwindow.ui. So i want to use this way in qml. Correct me if i'm wrong

                p3c0P 1 Reply Last reply
                0
                • jsulmJ Offline
                  jsulmJ Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by
                  #8

                  This way you will get two windows - just because you create two of them. If you only want to use QML for your UI then there is no need for MainWindow at all. You can use signals/slots without MainWindow.

                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                  1 Reply Last reply
                  0
                  • V vibolvireak

                    the default is like this. But i just think i want to include a mainwindow class because it easy to connect with a slot and signal. As i see in qt application there should be main.cpp, mainwindow.cpp, mainwindow.h and also mainwindow.ui. So i want to use this way in qml. Correct me if i'm wrong

                    p3c0P Offline
                    p3c0P Offline
                    p3c0
                    Moderators
                    wrote on last edited by
                    #9

                    @vibolvireak What is the root Item of your QML file ?
                    QQuickWidget does not support using windows as a root item. You will need to change it to Item.

                    157

                    JoeBermejalesJ 1 Reply Last reply
                    0
                    • P Offline
                      P Offline
                      prat22
                      wrote on last edited by
                      #10

                      your QQmlApplicationEngine engine; looks to be a local object which will go out of scope as soon as your constructor returns. try to make it member of your class and you will be able to see it.

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                      0
                      • p3c0P p3c0

                        @vibolvireak What is the root Item of your QML file ?
                        QQuickWidget does not support using windows as a root item. You will need to change it to Item.

                        JoeBermejalesJ Offline
                        JoeBermejalesJ Offline
                        JoeBermejales
                        wrote on last edited by JoeBermejales
                        #11

                        @p3c0 said in Calling qml on mainwindow:

                        @vibolvireak What is the root Item of your QML file ?
                        QQuickWidget does not support using windows as a root item. You will need to change it to Item.

                        You really saved my day, thanks, the QML was defined as a Window and when I tried to open in my app it always opened a new window. Now it works fine: this is a main window with a qml map inserted... it is an example about how inserting qml widgets into your app could help... Location and maps are not supported for c++

                        0_1542291644528_example qquickwidget qml on c++ main window.jpg

                        http://reparacionplotter.com

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