Calling qml on mainwindow

[vibolvireak]

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.

[p3c0]

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

[vibolvireak]

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. 

3. if i use qquickwidget it will see the 2 window main.qml, mainwindow.ui.qml will launch at the same time.

[jsulm]

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.

[vibolvireak]

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..

[jsulm]

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?

[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

[jsulm]

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.

[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.

[prat22]

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.

[JoeBermejales]

@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++