no such slot Qt异常

no such slot Qt错误
     在编译Qt程序的时候出现No such slot ....的错误     有Q_OBJECT   
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);

    this->setWindowFlags(Qt::FramelessWindowHint);//去掉标题栏
    QPalette palette1=this->palette();
    palette1.setBrush(QPalette::Window,QBrush(QPixmap("./images/background.png")));
    this->setPalette(palette1);
    this->setAutoFillBackground(true);
    //加入背景图片
    myCom = new Posix_QextSerialPort("/dev/ttyS0",QextSerialBase::Polling);//定义串口对象，指定串口名和查询模式
    
           
    this->threadSendMessage =new ThreadSendMessage;
    this->threadSendMessage->start();
    QObject::connect(threadSendMessage, SIGNAL(send1(QString)),
                      threadSendMessage, SLOT(sendmotor(QString)));
    QObject::connect(threadSendMessage, SIGNAL(send2(QString)),
                      threadSendMessage, SLOT(sendbuzzer(QString)));


class Widget : public QWidget {
    Q_OBJECT
public:
    Widget(QWidget *parent = 0);
    ~Widget();
    
protected:
    void changeEvent(QEvent *e);
    
public:
    Ui::Widget *ui;
    Posix_QextSerialPort *myCom;
    ThreadSendMessage *threadSendMessage;
    QTimer *readTimer;
    QTimer *readTimer1;
    QTimer *readTimer3;
    QTimer *readTimer2;
    //int SendMsg();
    //void addNum(char key);
public slots:
    void sendmotor(QString);
    void sendbuzzer(QString);

程序片段在这了       求教各位大侠






    
------解决方案--------------------
而且信号接收者应该是this而不是threadSendMessage
------解决方案--------------------
需要看看threadSendMessage的头文件，有没有声明信号和槽呢？
都是在一个类里面没有必要使用信号和槽吧？而且信号也不是Qt提供的，是自己定义的。