C++和QML混合编程

2023-12-14 16:32 由飞说晓事发表于 #后端开发

一、QML访问C++方法

Qt元对象系统中注册C++类，在QML中实例化、访问。
C++中实例化并设置为QML上下文属性，在QML中直接使用。

比较：方法1可以使C++类在QML中作为一个数据类型，例如函数参数类型或属性类型，也可以使用其枚举类型、单例等，功能更强大。

二、QML访问C++条件

派生自QObject类或QObject类的子类
使用Q_OBJECT宏

三、QML访问C++举例

使用方法1

信号与槽

#ifndef GEMINI_H  
#define GEMINI_H  
#include <QObject>  
#include <QDebug>  
class Gemini : public QObject  
{  
    Q_OBJECT  
signals:    //1、先定义“信号”
    void begin();   
public slots:  //1、先定义“槽”
    void doSomething() {  
        qDebug() << "Gemini::doSomething() called";  
    }  
};  
#endif

#include <QGuiApplication>  
#include <QQmlApplicationEngine>  
#include <QtQml>  
#include <Gemini.h>  
int main(int argc, char *argv[])  
{  
    QGuiApplication app(argc, argv);  
    qmlRegisterType<Gemini>("Union.Lotto.Gemini", 1, 0, "Gemini");  //一.注册c++类
    QQmlApplicationEngine engine;  
    engine.load(QUrl(QStringLiteral("qrc:///main.qml")));  
    return app.exec();  
}

import QtQuick 2.2  
import QtQuick.Window 2.1  
import Union.Lotto.Gemini 1.0  //二.导入
Window {  
    visible: true  
    width: 360; height: 360  
    title: "Union Lotto Game"  
    color: "white"  
    MouseArea {  
        anchors.fill: parent  
        onClicked: {  
            gemini.begin()  //2.调用类信号
        }  
    }  
    Gemini {  
        id: gemini  
        onBegin: doSomething()  //2.调用类槽
    }  
}

2、枚举类型

#ifndef GEMINI_H  
#define GEMINI_H  

#include <QObject>  
#include <QDebug>  
class Gemini : public QObject  
{  
    Q_OBJECT  
    Q_ENUMS(BALL_COLOR)  //1、先定义。枚举类型在QML中使用，就用到了Q_ENUMS()宏
public:  
    Gemini() : m_ballColor(BALL_COLOR_YELLOW) {  
        qDebug() << "Gemini::Gemini() called";  
    }  
    enum BALL_COLOR {  
        BALL_COLOR_YELLOW,  
        BALL_COLOR_RED,  
        BALL_COLOR_BLUE,  
        BALL_COLOR_ALL  
    };  
signals:  
    void begin();  
public slots:  
    void doSomething(BALL_COLOR ballColor) {  
        qDebug() << "Gemini::doSomething() called with" << ballColor;  
        if(ballColor != m_ballColor) {  
            m_ballColor = ballColor;  
            qDebug() << "ball color changed";  
        }  
    }  
private:  
    BALL_COLOR m_ballColor;  
};  
#endif

import QtQuick 2.2  
import QtQuick.Window 2.1  
import Union.Lotto.Gemini 1.0  
Window {  
    visible: true  
    width: 360; height: 360  
    title: "Union Lotto Game"  
    color: "white"  
    MouseArea {  
        anchors.fill: parent  
        onClicked: {  
            gemini.begin()  
        }  
    }  
    Gemini {  
        id: gemini  
        onBegin: doSomething(Gemini.BALL_COLOR_RED)  //2.调用，在QML中使用枚举类型的方式是<CLASS_NAME>.<ENUM_VALUE>
    }  
}

3、成员函数

#ifndef GEMINI_H  
#define GEMINI_H  

#include <QObject>  
#include <QDebug>  
class Gemini : public QObject  
{  
    Q_OBJECT  
    Q_ENUMS(BALL_COLOR)  
public:  
    Gemini() : m_ballColor(BALL_COLOR_YELLOW) {  
        qDebug() << "Gemini::Gemini() called";  
    }  
    enum BALL_COLOR {  
        BALL_COLOR_YELLOW,  
        BALL_COLOR_RED,  
        BALL_COLOR_BLUE,  
        BALL_COLOR_ALL  
    };  
    Q_INVOKABLE void stop() {  //1、定义。访问的前提是public或protected成员函数，且使用Q_INVOKABLE宏
        qDebug() << "Gemini::stop() called";  
    }  
signals:  
    void begin();  
public slots:  
    void doSomething(BALL_COLOR ballColor) {  
        qDebug() << "Gemini::doSomething() called with" << ballColor;  
        if(ballColor != m_ballColor) {  
            m_ballColor = ballColor;  
            qDebug() << "ball color changed";  
        }  
    }  
private:  
    BALL_COLOR m_ballColor;  
};  
#endif

import QtQuick 2.2  
import QtQuick.Window 2.1  
import Union.Lotto.Gemini 1.0  
Window {  
    visible: true  
    width: 360; height: 360  
    title: "Union Lotto Game"  
    color: "white"  
    MouseArea {  
        anchors.fill: parent  
        onClicked: {  
            gemini.begin()  
            gemini.stop()  //2、调用，在QML中访问C++的成员函数的形式是<id>.<method>
        }  
    }  
    Gemini {  
        id: gemini  
        onBegin: doSomething(Gemini.BALL_COLOR_RED)  
    }  
}

4、C++类的属性

#ifndef GEMINI_H  
#define GEMINI_H  

#include <QObject>  
#include <QDebug>  
class Gemini : public QObject  
{  
    Q_OBJECT  
    Q_ENUMS(BALL_COLOR)  
    Q_PROPERTY(unsigned int ballNumber READ ballNumber WRITE setBallNumber NOTIFY ballNumberChanged)  //1、定义，Q_PROPERTY()宏，用来在QObject派生类中声明属性。
public:  
    Gemini() : m_ballColor(BALL_COLOR_YELLOW), m_ballNumber(0) {  
        qDebug() << "Gemini::Gemini() called";  
    }  
    enum BALL_COLOR {  
        BALL_COLOR_YELLOW,  
        BALL_COLOR_RED,  
        BALL_COLOR_BLUE,  
        BALL_COLOR_ALL  
    };  
    unsigned int ballNumber() const {  
        return m_ballNumber;  
    }  
    void setBallNumber(const unsigned int &ballNumber) {  
        if(ballNumber != m_ballNumber) {  
            m_ballNumber = ballNumber;  
            emit ballNumberChanged();  
        }  
    }  
    Q_INVOKABLE void stop() {  
        qDebug() << "Gemini::stop() called";  
    }  
signals:  
    void begin();  
    void ballNumberChanged();  
public slots:  
    void doSomething(BALL_COLOR ballColor) {  
        qDebug() << "Gemini::doSomething() called with" << ballColor;  
        if(ballColor != m_ballColor) {  
            m_ballColor = ballColor;  
            qDebug() << "ball color changed";  
        }  
    }  
private:  
    BALL_COLOR m_ballColor;  
    unsigned int m_ballNumber;  
};  
#endif

import QtQuick 2.2  
import QtQuick.Window 2.1  
import Union.Lotto.Gemini 1.0  
Window {  
    visible: true  
    width: 360; height: 360  
    title: "Union Lotto Game"  
    color: "white"  
    MouseArea {  
        anchors.fill: parent  
        onClicked: {  
            gemini.begin()  
            gemini.stop()  
            gemini.ballNumber = 10  //2、调用，Gemini类中的ballNumber属性可以在QML中访问、修改，访问时调用了ballNumber()函数，
                                    //        修改时调用了setBallNumber()函数，同时还发送了一个信号来自动更新这个属性值。
        }  
    }  
    Gemini {  
        id: gemini  
        onBegin: doSomething(Gemini.BALL_COLOR_RED)  
        onBallNumberChanged: console.log("new ball number is", ballNumber) // 10  
        Component.onCompleted: console.log("default ball number is", ballNumber) // 0  
    }  
}

备注：1、参考网址：https://zhuanlan.zhihu.com/p/633999343

2、本文只为个人学习笔记，其他第三方可以任意使用。

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一、QML访问C++方法

二、QML访问C++条件

三、QML访问C++举例