Cannot modify Qml propriety from Cpp
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I've this main.cpp code:
@int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv); //preparo l'applicazione
QQmlApplicationEngine engine(QUrl("qml/main.qml")); //carico l'interfaccia
QObject *radice = engine.rootObjects().value(0); //identifico la radice
QQuickWindow *applicationwindow = qobject_cast<QQuickWindow *>(radice); //acquisisco in C++ l'ogg QML ApplicationWindow
if ( !applicationwindow )
{
qWarning("Error: Your root item has to be a Window.");
return -1;
}QObject *button = radice->findChild<QObject*>("buttonOpenCloseCom",Qt::FindChildrenRecursively); if (button) { button->setProperty("text", "Open"); qDebug()<<"find!"; } applicationwindow->show(); return app.exec();}@
and this main.qml file:
@import QtQuick 2.1
import QtQuick.Controls 1.0
import QtQuick.Controls.Styles 1.0
import QtQuick.Layouts 1.0ApplicationWindow
{
id: applicationwindow;
/Interface config/
title: appname
property int margin: 11
property string appname: "Controller 0.1"
property int coordsFontSize: 25
property string buttonComText: "Open/Close"
//width: mainLayout.implicitWidth + 2 * margin
//height: mainLayout.implicitHeight + 2 * margin
width: 1024
height: 768
minimumWidth: 1024
minimumHeight: 768RowLayout { id: mainLayout anchors.fill: parent anchors.margins: margin Layout.fillWidth: true ColumnLayout { id: leftColumn anchors.bottom: parent.bottom anchors.bottomMargin: 0 anchors.top: parent.top anchors.left: parent.left Layout.fillWidth: false Layout.preferredWidth: parent.width/2 //Layout.preferredHeight: parent.height/2 GroupBox { id: comGroupBox title: "COM Layer" Layout.fillWidth: true RowLayout { id: rowlayout1 anchors.top: parent.top anchors.fill: parent anchors.margins: 20 spacing: 5 ComboBox { id: comboComs model: [ "COM1", "COM2", "COM3" ] function test() { console.log("TEST OK"); } onClipChanged: {console.log("azz")} } Button { id: buttonOpenCloseCom objectName: buttonOpenCloseCom text:applicationwindow.buttonComText enabled: true } } } }}@
I need to change the text of the button that has the objectName proprety "buttonOpenCloseCom", but the code defined in main.cpp doesn't work, and I'm not able to understand why. I've followed examples like "this":http://qt-project.org/doc/qt-5.1/qtqml/qtqml-cppintegration-interactqmlfromcpp.html but it seem that the button object is not found by the findChild method... infact the qDebug print is not performed...
Can anyone help me? -
I guess you need to set that property after even loop is started in app.exec().
Otherwise, the code seems to be correct (although there is no need to modify buttonOpenCloseCom, when you can just modify buttonComText in ApplicationWindow).
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Hi, thanks for the answer.
I've changed the code:
@int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv); //preparo l'applicazione
QQmlApplicationEngine engine(QUrl("qml/main.qml")); //carico l'interfaccia
QObject *radice = engine.rootObjects().value(0); //identifico la radice
QQuickWindow *applicationwindow = qobject_cast<QQuickWindow *>(radice); //acquisisco in C++ l'ogg QML ApplicationWindow
if ( !applicationwindow )
{
qWarning("Error: Your root item has to be a Window.");
return -1;
}
applicationwindow->show();
return app.exec();QObject *button = radice->findChild<QObject*>("buttonOpenCloseCom",Qt::FindChildrenRecursively); if (button) { button->setProperty("text", "Open"); qDebug()<<"found!"; } else { button->setProperty("text", "Open"); qDebug()<<"not found!"; }}@
but there is no output.
The problem persists!I've also tried to change the buttonComText in ApplicationWindows, but the result is the same.
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There is yet the objectName proprety.
I've tried this solution... but doesn't work.
[quote author="wspilot" date="1376930837"]Try this:
objectName: "buttonOpenCloseCom"[/quote] -
Excuseme but in the code:
@
Button
{
id: buttonOpenCloseCom
objectName: buttonOpenCloseCom
text:applicationwindow.buttonComText
enabled: true
}
@objectName: “buttonOpenCloseCom” there is![/quote]
what is the problem you talk about?!
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Put it in quotes: ". Not just string but "string".
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I've understand what you mean, and I've tried with the correction, but the result is the same as before.
Debugging i've see that the root object is correctly the "applicationwindow",
but when I try to find the child, it fails and return a null pointer...
in "this":http://qt-project.org/doc/qt-5.1/qtqml/qtqml-cppintegration-interactqmlfromcpp.html#loading-qml-objects-from-c reference it used QQuickView, and not QQuickWindow to handle the root object...
Could it be a problem?
If yes, how can I resolve it? any suggestions? -
I've modified the code:
@int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv); //preparo l'applicazione
QQmlApplicationEngine engine(QUrl("qml/main.qml")); //carico l'interfaccia
QObject *radice = engine.rootObjects().value(0); //identifico la radice
QQuickWindow *applicationwindow = qobject_cast<QQuickWindow *>(radice); //acquisisco in C++ l'ogg QML ApplicationWindow
if ( !applicationwindow )
{
qWarning("Error: Your root item has to be a Window.");
return -1;
}
QObject button = radice->findChild<QObject>("buttonOpenCloseCom",Qt::FindChildrenRecursively);
if (button)
{
button->setProperty("text", "Open");
qDebug()<<"found!";
}
else
{
button->setProperty("text", "Open");
qDebug()<<"not found!";
}applicationwindow->show(); return app.exec();}@
but is the same as before...
[quote author="mranger90" date="1376947874"]The problem is that you make the change after the return() statement.
Nothing after that will be executed.[/quote] -
One drawback of QML is that it's mightily hard to explain certain things... In order for this to work (IMO) you need to do that property manipulation outside of "main.cpp":https://github.com/sierdzio/closecombatfree/blob/master/src/ccfmain.cpp so for example in a QObject that gets initialised somewhere later. Same as with QWidgets or console apps in Qt: you need to have a working event loop for moc to work.
One possible alternative would be to modify the property using Qt::QueuedConnection, or the infamous singleshot QTimer.
