QML Property Binding with QT C++

╰+哭是因爲堅強的太久メ 2022-07-24 10:13 152阅读 0赞

今天就分享一下，在c++中定义qml中的属性。

QT QML will helps us to build the User Interface quickly and elegantly, It acts as a UI Presentation Layer. There should be a way of communicating data from C++ to QML. This article describes the simplest way of data binding between QML and C++ which uses the following features:

三步走：  
**1 Q\_PROPERTY in C++ which will give the set and get methods for C++ as well as QML.**  
**2 QT way of registering the C++ Object, which makes the way to import that object in QML.**  
**3 In QML, we can set and get the properties by attaching the C++ object to it.**

直接来代码：

**//C++ Header File**

#pragma once
    
     #include <QObject>
    
    
     class propertybinding : public QObject
      {
        Q_OBJECT
        Q_PROPERTY(QString valueToQML READ valueToQML WRITE setValueToQML NOTIFY valueToQMLChanged)
    
        public:
    
        explicit propertybinding(QObject *parent = 0);
        ~propertybinding();
        QString valueToQML() const;
        void setValueToQML(QString);
    
    signals:
         void valueToQMLChanged();
    
    private:
        QString _valueString;
    };

**// C++ Source File**

#include "propertybinding.h" 
    
    propertybinding::propertybinding(QObject *parent) : QObject(parent) { } 
    
    propertybinding::~propertybinding() { }
    
    void propertybinding::setValueToQML(QString pData) {
        _valueString = pData;
        emit valueToQMLChanged();
    } 
    
    QString propertybinding::valueToQML() const {
        return _valueString;
    }

**// QML Code**

import QtQuick 2.3
    import PropertyBinding 1.0
    
    Rectangle {
        property alias mouseArea: mouseArea 
        // Creating the Instance fro Property Binding
    
        PropertyBinding {
            id: propertyBinding
        }
    
        width: 400
        height: 400
        MouseArea {
            id: mouseArea
            anchors.rightMargin: 0
            anchors.bottomMargin: 0
            anchors.leftMargin: 0
            anchors.topMargin: 0
            anchors.fill: parent
    
           Text {
                id: text1
                x: 115
                y: 27
                width: 145
                height: 32
                text: qsTr("Property Binding")
                font.pixelSize: 22
            }
          Text {
                id: text2
                x: 109
                y: 103
                width: 41
                height: 15
                text: qsTr("Value:")
                font.pixelSize: 12
            }
            Row {
                id: row1
                x: 88
                y: 73
                width: 200
                height: 75
            }
          Text {
                id: text3
                x: 190
                y: 103
                width: 53
                height: 15
                text: propertyBinding.valueToQML // get the Value to QML from C++ using get Property
                font.pixelSize: 12
            }
         }
        Component.onCompleted: propertyBinding.valueToQML = 
        "QML to C++ Property Binding" // set the Value from QML to C++ using set Property
    }