Updating Qlabel image

valerio.j

Hello,

I have a small switch function running that I want to update the image of a label depending on the result. The issue I have is that all images are only updated at the end of the run. How can I update each image as each case is evaluated?

int MainWindow::readADC(int range)
{
    QPixmap stat_GO (":/res/images/stat_GO.png");
    QByteArray data;
    bool ok = false;
    float r = 0.0;

    switch (range)
    {
    case 24:
        serial->waitForReadyRead(1000);
        data = serial->readAll();
        qDebug() << data;
        r = data.toFloat(&ok);
        if (!ok) qDebug() << "24VDC Conversion Failed";
        qDebug() << r;

        if ((r > 23.2) && (r < 24.8))   //Check tolerance (3.3%)
            ui->_tstr24Vok->setPixmap(stat_GO);
        return 1;
        break;

    case 3:
        serial->waitForReadyRead(1000);
        data = serial->readAll();
        qDebug() << data;
        r = data.toFloat(&ok);
        if (!ok) qDebug() << "3.3VDC Conversion Failed";
        qDebug() << r;

        if ((r > 3.2) && (r < 3.4))   //Check tolerance (3%)
             ui->_but3v3Vok->setPixmap(stat_GO);
        return 1;
        break;

    case 12:
        serial->waitForReadyRead(1000);
        data = serial->readAll();
        qDebug() << data;
        r = data.toFloat(&ok);
        if (!ok) qDebug() << "12VDC Conversion Failed";
        qDebug() << r;
        
        if ((r > 11.6) && (r < 12.4))   //Check tolerance (3.3%)
        ui->_but12Vok->setPixmap(stat_GO);
        return 1;
        break;
    }
    return 0;
}

micland

I don't know what you're doing after returning from that method but it seems that the event loop is still busy so the label is not updated immediately.
Try calling ui->myLabel->repaint(); to enforce an update.

valerio.j

@micland
After the return is validated it just continues on basically repeating similar tasks.
adding ui->myLabel->repaint(); after each label change does what I'mm looking for. Thanks.

micland

If you're running your tasks in an endless loop and can't move it to a background thread your UI will freeze so instead of calling repaint() it might be better to call QCoreApplication::processEvents() to process all queued events (unless you want ensure that any user input is blocked until you leave your task loop).