Static Variables and Static Class Members - 2023

 

Introduce component construction, destruction, and dynamic loading knowledge.

Objects/Components all have C++-like constructors and destructors

 

• onCompletedObject construction completes automatic execution;
• onDestructionExecuted automatically before the object is destroyed.
•  

QtObject {
    Component.onCompleted: console.log("Completed")
    Component.onDestruction: console.log("Destruction")
}

 

Load components using Loader

 

• ComponentMust have a subspace to instantiate;
• onProgressChangedThe loading progress of the component can be obtained.

Component {
    id: component
    Text {
        text: "Component"
    }
}

Loader {
    sourceComponent: component
    onProgressChanged: console.log(progress)
}

 

Dynamically load Qml components (1)

 

• prototype:

1. qmlDescribe the statement for the qml component;
2. parentTo attach to that parent control;
3. filepathError reporting during loading for redirection to file

object createQmlObject(qml, 
                       object parent, 
                       string filepath)

• example

var object = Qt.createQmlObject('import QtQuick 2.0; Rectangle {color: "blue"; width: 50; height: 50}',
                                   root,
                                   "error.txt");

 

Dynamically load Qml components (2)

 

• prototype:

1. urlIt is a qml file (you can also load a network qml file);
2. modeMode for creating qml (synchronous or asynchronous);
3. parentDesignate a control as the parent control;
4. objectas an additional attribute.

object createComponent(url, mode, parent)
object createObject(parent, object properties)

•  
• Example:
•  

var component = Qt.createComponent("MyComponent.qml");
if (component.status == Component.Ready)
    component.createObject(parent, {x: 100, y: 100});