Here is the part of my code.

void MainWindow::on_pushButtonPT_Lantest_clicked()
{
    if(!LanTabClick)
    {
        LanTabClick=true;
        initPTLan();
        //QMessageBox::information(NULL,"information","Begin lan test",QMessageBox::Cancel);
        MsgBox->information(NULL,"information","Begin lan test",QMessageBox::Cancel);
        /*MsgBox.setText("Begin lan test");
        MsgBox.setIcon(QMessageBox::Information);
        MsgBox.setStandardButtons(QMessageBox::Cancel);
        MsgBox.exec();*/
    }
}

void MainWindow::Lanshow(QString speed)
{
    qDebug()<<"forenex victor speed:"<<speed;
    QString check,eth1;
    eth0_destination="/sbin/route -n | /bin/grep 255 | /bin/grep eth0";
    qDebug("In Lanshow");
    if(!Lanpingperf->twoLAN)
    {
        qDebug("In Lanshow ,not twoLan");
        if(speed.indexOf("failed")!=-1 || speed=="" || speed.right(11)=="unreachable")
        {
            qDebug("speed failed");
            ui->lineEditPT_LANResult->setText("Failed");
            ui->pushButtonPT_LAN_ResultLight->setStyleSheet("QPushButton{background-color:red;}");
            test_result[12]=false;
            ui->textEditPT_LAN->setText("LAN is not working. Cannot ping 8.8.8.8!!!! ");
            LanTabClick=false;
        }
        else
        {
            qDebug("speed Pass");
            ui->lineEditPT_LANResult->setText("Pass");
            ui->pushButtonPT_LAN_ResultLight->setStyleSheet("QPushButton{background-color:green;}");
            test_result[12]=true;
            ui->textEditPT_LAN->setText("LAN speed = "+speed);
            LanTabClick=false;
        }
        MsgBox->close();
  }
}

I will enable the Messagebox in function on_pushButtonPT_Lantest_clicked then wanna close it in function Lanshow.
However, the message box shows perfectly but cannot close it when running MsgBox->close().

What did I miss?

Thanks in Advanced!