QMLSignalSlot

    id: rectangle1
    signal receiveText(string str)    // c++ 发送信号， qml 接收
    signal sendText(string str)       // qml 发送信号， c++ 接收
    Rectangle
    {
        anchors.fill: parent
        color:  "red"
        radius: 10
        Rectangle{
            id:reg
            width: 100
            height: 100
            anchors.centerIn: parent
            radius: 50
            color: "#cccccc"
            Text {
                id: name
                anchors.centerIn: parent
                font.pixelSize: 18
                font.bold: true
                text: qsTr("")
            }
            MouseArea
            {
                anchors.fill: parent
                onClicked:
                {
                    sendText("123456")  // 鼠标点击 发送信号
                    name.text = "Send"
                    num.start()
                }
            }
            NumberAnimation{
                id:num
                target: reg
                property: "scale"
                from:1
                to:0.3
                duration: 2000
            }
            NumberAnimation{
                id:num1
                target: reg
                property: "scale"
                to:1
                duration: 2000
            }
        }
    }
    onReceiveText:   // 当 c++ 发送信号， qml 接收
    {
        name.text = "Recive"
        console.log("aaaaaaaaaaaaaaaaaaaaaaa")
        num1.start()
    }
}

QQuickItem *item = ui->quickWidget->rootObject();

connect((QObject*)(item),SIGNAL(sendText(QString)),this,SLOT(receiveFromQml(QString)));
//  这里qml 的槽函数， 是通过qnl 的信号来触发的。 所以只能通过按钮的信号来触发 qml 的信号
connect(this,SIGNAL(sendToQml(QString)),(QObject*)(item),SIGNAL(receiveText(QString)));
// c++ 按钮点击发送信号。 
connect(ui->pushButton,&QPushButton::clicked,[this]
{
    emit sendToQml("yangsen");
});