//拖拽一个QQuickWidget

c++端和qml通信的桥梁
找到qml的main.qml的路径

   ui->quickWidget->setSource(QUrl::fromLocalFile("../../../code/main.qml"));
    // QML 与 Qt Widgets 通信
    //窗口就成了一个类实例对象
    pRoot = (QObject*)ui->quickWidget->rootObject();

此时目录结构，上面是c++，下面是qml

如何使用信号槽
c++端发给qml端

//c++端写一个信号触发qml端的信号
 if (pRoot != NULL)
    {
        
        connect(ui->btn_circle, SIGNAL(clicked()), pRoot, SIGNAL(cSignal()));
	}

//qml端这么写

 signal cSignal
onCSignal()
{

}

qml端发给c++端

```connect(pRoot,SIGNAL(qml_ClickedCircle(QVariant,QVariant,double,double,double)),this,SLOT(slot_qml_CircleClicked(QVariant,QVariant,double,double,double)));