QLabel内嵌在一个widget窗体内，根据鼠标移动，移动labe，但是画面不刷新,

除非我拖动整个窗体的时候，画面才刷新

好难啊好难啊好难啊好难啊好难啊好难啊好难啊好难啊好难啊好难啊

 bool Widget::event(QEvent *event)
{
    bool flipAction = false;
    static float last_x = 0.0f;
    static float touchBeginLastX = 0.0f;

    int deltaX = 0;
    float acceleration = 0.0f;

    switch(event->type()) {
    case QEvent::MouseButtonPress: {
        flipAction = true;
        m_time.start();
        const QMouseEvent *mouseEvent = static_cast<const QMouseEvent *>(event);
        last_x = mouseEvent->x();
        touchBeginLastX = mouseEvent->x();
    }
        break;

    case QEvent::MouseMove: {
        flipAction = true;
        const QMouseEvent *mouseEvent = static_cast<const QMouseEvent *>(event);
        deltaX = mouseEvent->x() - last_x;
        last_x = mouseEvent->x();
    }
        break;

    case QEvent::MouseButtonRelease: {
        flipAction = true;
        int elapseTime = m_time.elapsed();
        const QMouseEvent *mouseEvent = static_cast<const QMouseEvent *>(event);
        deltaX = mouseEvent->x() - last_x;
        acceleration = (mouseEvent->x() - touchBeginLastX) / elapseTime;
    }
        break;
    default:
        break;
    }

    if(flipAction) {
        qDebug() << deltaX;
        QPoint targetPos = ui->label->pos()+QPoint(deltaX,0);
        qDebug() << ui->label->pos();
        ui->label->setGeometry(targetPos.x(), targetPos.y(), ui->label->width(), ui->label->height());
//        ui->label->move(targetPos);
        ui->label->repaint();
        repaint();
        moveEvent(NULL);
    }

    return false;
}

在鼠标移动的槽函数里来update()一下widget

update,repaint都没有效果