QWidget实现QDialog exec() 模态效果

//.h
public:
    int exec();
private:
    QPushButton *m_BtnOK;
    QPushButton *m_BtnCancel;
    int m_Result;
    QEventLoop *m_Loop;
protected:
    void closeEvent(QCloseEvent *event);
public slots:
    void btnOKSlot();
    void btnCancelSlot();

//.cpp
this->setWindowModality(Qt::ApplicationModal);
void MessageBox::btnOKSlot()
{
    m_Result=1;
    this->close();
}
void MessageBox::btnCancelSlot()
{
    m_Result=0;
    this->close();
}
int MessageBox::exec()
{
    m_Result=-1;
    this->show();
    m_Loop=new QEventLoop(this);
    m_Loop->exec();
    return m_Result;
}
void MessageBox::closeEvent(QCloseEvent *event)
{
    if(m_Loop!=NULL)
    {
        m_Loop->exit();
    }
    event->accept();
}