QML与C++交互

1、定义业务C++类

#ifndef BUSINESS_H
#define BUSINESS_H
#include <QObject>
class Business : public QObject
{
    Q_OBJECT
public:
    explicit Business(QObject *parent = nullptr);
    Q_PROPERTY(int mode READ getMode WRITE setMode NOTIFY sigModeChanged);//定义属性
public: 
   //setts&getters
    void setMode(int);
    int getMode();
public slots:
	//直接可以在QML里调用的接口
    Q_INVOKABLE void stop();
    Q_INVOKABLE void start();
signals:
    void sigModeChanged();
    void sigTimeChanged(QString tt);
private:
    int mode_;
    class QTimer *timer_;
};
#endif // BUSINESS_H

#include "business.h"
#include <QTimer>
#include <QDateTime>
Business::Business(QObject *parent)
    : QObject(parent)
    ,mode_(0)
{
    timer_ = new QTimer(this);
    connect(timer_,&QTimer::timeout,this,[this](){
        QString timestr;
        //不同的模式
        switch (mode_) {
        case 0:
            timestr = QDateTime::currentDateTime().toString("MM-dd-yyyy hh:mm:ss");
            break;
        case 1:
            timestr = QDateTime::currentDateTime().toString("yyyy/MM/dd hh:mm:ss");
            break;
        default:
            timestr = QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss");
            break;
        }
        sigTimeChanged(QString("Mode%1:").arg(mode_) + timestr);
    });
}
void Business::setMode(int m)
{
    if(mode_ != m)
    {
        mode_ = m;
        sigModeChanged();
    }
}
int Business::getMode()
{
    return mode_;
}
void Business::stop()
{
    timer_->stop();
}
void Business::start()
{
    timer_->start(1000);
}

2、定义QML

import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 1.4
import Business.test 1.0
Window {
   visible: true
   width: 640
   height: 480
   title: qsTr("QML Interactive With C++ Test ")
   property alias value : id_txt.text

   Rectangle{
       id:jeams
       width: 300
       height: 40
       anchors.horizontalCenter: parent.horizontalCenter
       Text {
           id:id_txt
           anchors.centerIn: parent
           text: qsTr("QML Interactive With C++")
           color: "black"
       }
       color: "yellow"
   }

   Button{
       id:btnstart
       width: 80
       height: 40
       text: "开始"
       anchors.centerIn: parent
       anchors.horizontalCenterOffset: -40
      onClicked: {
          id_business.start()
      }
   }
   Button{
       id:btnstop
       width: 80
       height: 40
       text: "停止"
       anchors.centerIn: parent
       anchors.horizontalCenterOffset: 40
       onClicked: {
          id_business.stop()
      }
   }
   Button{
       id:leftbtn
       width: 80
       height: 40
       text: "模式0"
       anchors.left: parent.left
       anchors.bottom: parent.bottom
       onClicked: {
          id_business.mode = 0
      }
   }
   Button{
       id:centerbtn
       width: 80
       height: 40
       text: "模式1"
       anchors.horizontalCenter: parent.horizontalCenter
       anchors.bottom: parent.bottom
       onClicked: {
          id_business.mode = 1
      }
   }
   Button{
       id:rightbtn
       width: 80
       height: 40
       text: "模式2"
       anchors.right: parent.right
       anchors.bottom: parent.bottom
       onClicked: {
          id_business.mode = 2
      }
   }

   MyBusiness{
       id: id_business
       onSigTimeChanged:{
           value = tt
       }
   }
}

3、注册

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include "business.h"

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    QGuiApplication app(argc, argv);
    qmlRegisterType<Business>("Business.test",1,0,"MyBusiness");
    QQmlApplicationEngine engine;
    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();
}

4、效果