how to set full screen when I use QQuickView in Qt?

Question

When I create a new project in Qt, Qt use QQmlApplicationEngine to load qml file, rootObject in qml file is Window, like :

Window {
    id: root
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")
    Component.onCompleted: {
        root.showFullScreen()
    }
}

And I can use method showFullScreen to display it full my screen (full my monitor)

But, if I use QQuickView to show qml file, I can't make it full screen, I don't find any function with the same, I use like that:

QQuickView view;
view.setSource(QUrl("qrc:/main.qml"));
view.setWindowState(Qt::WindowFullScreen);
view.setResizeMode(QQuickView::SizeRootObjectToView); //even when i call this method, it doesn't still work
view.show();

qml file with this case:

Rectangle{
    // rectangle has with, hight, it still doesn't work
    color: "green"
}

Please guide me how to display full screen with QQuickView ? Thanks so much, I appreciate with any help !

Answer 1

In my opinion, there's no much difference setting main window to full-screen for QQuickView. It inherits QWindow and also has showFullScreen method. Therefore you can invoke this method from c++ instead of your view.show();. If, on the other hand, you need to switch to full-screen from QML then you have to expose your QQuickView object to QML, as described here:

#include <QGuiApplication>
#include <QQuickView>
#include <QQmlEngine>
#include <QQmlContext>

int main(int argc, char *argv[])
{
  QGuiApplication app(argc, argv);    
  QQuickView mainView;

  // expose mainView to QML, see
  // https://doc.qt.io/qt-6/qtqml-cppintegration-contextproperties.html
  mainView.setObjectName("mainView");
  mainView.engine()->rootContext()->setContextProperty("mainView", &mainView);

  mainView.show(); // we call mainView.show() before loading the qml file in
  // order to allow to override mainView.show() with mainView.showFullScreen()
  mainView.setSource(QUrl("qrc:/main.qml"));

  return app.exec();
}

Here's also the code of main.qml for reference:

import QtQuick 2
import QtQuick.Controls 2

Rectangle {
    id: rect
    color: "green"
    anchors.fill: parent

    Button {
        id: toggleFullScreen
        property bool isFullScreen: true
        text: "toggle full screen"
        anchors.centerIn: parent

        onPressed: {
            toggleFullScreen.isFullScreen = !toggleFullScreen.isFullScreen
            executeFullScreen()
        }
    }

    function executeFullScreen() {
        if(toggleFullScreen.isFullScreen)
            mainView.showFullScreen()
        else
            mainView.showNormal()
    }

    Component.onCompleted: {
        executeFullScreen()
    }
}

Answer 2

Use view.showFullScreen(); instead of view.setWindowState(Qt::WindowFullScreen);

QQuickView view;
view.setSource(QUrl("qrc:/main.qml"));
view.showFullScreen();