QML与C++之间通讯

第一步，在main.cpp文件加入C++类的包含

第二步，并在main.cpp代码中声明C++类的对象，并加入代码

    BoardLib boardlib;//声明C++类的对象
    engine.rootContext()->setContextProperty("boardlib",&boardlib);
   //在这里需要注意双引号内的字符，需要在QML文件中使用   "boardlib"

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "boardlib.h" //C++的类

int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;

//C++ 类和QML通讯需要加入如下代码
    BoardLib boardlib;
    engine.rootContext()->setContextProperty("boardlib",&boardlib);
//在这里需要注意双引号内的字符，需要在QML文件中使用   "boardlib"

    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);


    return app.exec();
}

第三步，在C++类头文件中声明QML中会引用到的函数

头文件，注意需要继承QObject类

#ifndef BOARDLIB_H
#define BOARDLIB_H
#include "boardctrllib.h"
#include <QObject>

class BoardLib:public QObject
{
    Q_OBJECT
public:
    BoardLib();
    ~BoardLib();

public:
   Q_INVOKABLE void onShowMsg();
};

#endif // BOARDLIB_H

源文件

#include "boardlib.h"
#include <QDebug>

BoardLib::BoardLib() {}

BoardLib::~BoardLib(){}

void BoardLib::onShowMsg()
{
    console.log("Hello World");
}

第四步，在QML文件中使用C++的函数

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15

Window {
    id:mainWindow
    width: 1024
    height: 768
    visible: true
    title: qsTr("TupCameraApp")
    color:"#0E3B73"
    visibility: "FullScreen"

        Rectangle{
        x:100
        y:100
        width: 100
        height: 100
        color: "red"
        MouseArea{
            anchors.fill: parent
            onClicked:{
                boardlib.onShowMsg()
            }
        }
    }
}