How do you access properties of a QML component in C++?
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Look at:
"Locating child objects in QML":http://doc.qt.nokia.com/4.7-snapshot/qtbinding.html#locating-child-objects -
I have seen that but isn't that for changing the properties in QML? I am trying to take properties from the QML object and use them as inputs for C++ functions.
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The last post helped quite a bit I am having trouble using it though can't seem to find any examples of people actually using it so not sure how I am supposed to implement that piece of code. In the form it is presented it isn't working for me. Do I need to use Q_PROPERTY macros or anything to make it work? Not really sure if what I need to make it work.
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Yes you need Q_PROPERTY in order for the moc (Meta Object Compiler) to add it to the generated MetaObject, so you can access it via these methods. If you have any further problems, just ask.
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@QObject *object = view.rootObject();
QObject textIn = object->findChild<QObject>(“textIn”);
textIn->setProperty("text","sampleText"); @See if this works.
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i have a similar problem. i managed to set a value from c++ in my qml file. the value is the x position of a qml rectangle, but when i change the value in c++ the rectangle isnt moved. What am i doing wrong?
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[quote author="Nazgul" date="1308039647"]i have a similar problem. i managed to set a value from c++ in my qml file. the value is the x position of a qml rectangle, but when i change the value in c++ the rectangle isnt moved. What am i doing wrong?[/quote]
How should we know, if you are not showing us what you are actually doing?
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I'll check to see if that works but here is something that does work really well
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QDeclarativeProperty property([name of element], "[name of property]");
@and then to call the property just do
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property.read()
property.write()
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and you can even do stuff like property.read().toString etc. this is what I was really looking for I think but thanks for all the help wouldn't have been able to find it without the leads.You still need stuff like
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QObject object = object->findChild<QObject>("rect");
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to use this thoughEdit: use @ tags to markup code sections please.
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c++ code
@QDeclarativeEngine engine;
QDeclarativeComponent component(&engine, url);
QObject *object = component.create();
if (object) {
object->setProperty("currentValue", newVal);
delete object;
object = NULL;
}@and my qml file:
@Item {
id: line
objectName: "line"
property real currentValue: 100
property real minimum: 0
property real maximum: 200
property int xMax: line.width - rect.width - 4
onCurrentValueChanged: { rect.x = 2 + (currentValue - minimum) * line.xMax / (maximum - minimum) }
signal valueChanged(real val)
width: 400
height: 20
Rectangle {
id: rect
x: 0; y: 0
width: 100; height: 20
color: "red"
MouseArea {
anchors.fill: parent
drag.axis: Drag.XAxis
drag.target: rect
drag.minimumX: 0
drag.maximumX: line.width - rect.width
onPositionChanged: {
line.currentValue = (maximum - minimum) * (rect.x-2) / line.xMax + minimum
line.valueChanged(line.currentValue)
}
}
}
}
@thanks in advance
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What is the delete statement doing on line 6 of your code? What do you expect to happen if you first set a property, and then immediately delete the object?
What you are doing here, is creating an object, setting a property on it, and then immediately disposing of it again. That seems like a rather useless thing to do. Instead, you should try to find the object you wish to manipulate, and then modify its properties. Or, perhaps better from a QML/declarative way of thinking kind-of-perspective, you should create a QObject derived object, give it properties for the position, insert it into your QML environment, and bind to these properties.
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@QObject* obj = mDeclarativeView->rootObject();
if (obj) {
obj->setProperty("currentValue", newVal);
}@ok, i wasnt sure about a memory leak because the method was create.
i changed my code to the above and made sure obj != null. obj is a qml object with name = "line"
thats fine so far but still the setProperty has no effect. -
no ideas about my problem?