How to access one checkbox in QML from .cpp in QT?

Question

Recently, I got a small problem, which is accessing the checkbox in qml from cpp in QT. So the problem is quite simple: I have a main.qml file, which has a checkbox, I want to update the "checked" property to true or false based on the configuration that I saved in QSettings when I launch the application. Currently, I have successfully load the setting from QSettings in cpp file when application startup. Then how to modify the "checked" property in this cpp file?

I tried this :http://doc.qt.io/qt-5/qtqml-cppintegration-interactqmlfromcpp.html and used the findChild function but it does not work.

1), I put import <QtQuick> in cpp file but i got error as QtQuick file can't be found.

2), I changed to "import <QtQuick/QQuickView>". Solved 1) but got new error for this line QObject* object = view.rootObject();:

cannot initialize a variable of type 'QObject *' with an rvalue of type 'QQuickItem *`

3), I changed QObject* object = view.rootObject(); this line to QQuickItem* object = view.rootObject(); and used QObject* acbox = object->findChild<QObject* >("acbox"); after that. (acbox is the objectName of that checkbox) Solved 2) but got new error:

Undefined symbols for architecture x86_64:
  "QQuickView::setSource(QUrl const&)", referenced from:
      ndn::TrayMenu::TrayMenu(QQmlContext*, ndn::Face&) in tray-menu.cpp.1.o
  "QQuickView::QQuickView(QWindow*)", referenced from:
      ndn::TrayMenu::TrayMenu(QQmlContext*, ndn::Face&) in tray-menu.cpp.1.o
  "QQuickView::~QQuickView()", referenced from:
      ndn::TrayMenu::TrayMenu(QQmlContext*, ndn::Face&) in tray-menu.cpp.1.o
  "QQuickView::rootObject() const", referenced from:
      ndn::TrayMenu::TrayMenu(QQmlContext*, ndn::Face&) in tray-menu.cpp.1.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Anyone has any suggestion? Thanks in advance!

Answer 1

you can use setproperty in cpp to set a property in qml and then bind that to the checked status in qml file check the following code

C++ part:

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

    QQmlApplicationEngine engine; 
    QQmlComponent component(&engine, QUrl("qrc:/main.qml"));
    QObject *object = component.create();
    object->setProperty("checkstatus", false);
    return app.exec();
}

QML part:

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    property bool checkstatus


    CheckBox {
        id:checkbox
        text: qsTr("checkbox1")
        checked: checkstatus
    }

}