main window doesn't open although program is running

[LeoC]

Hi,

I have a small gui that should display some voltage values that comes in over a serial port.
The thing is that the gui is not loaded after starting the programm, although I see the values comming in in the debug output. So the programm itself is running somehow.
When I remove the part where I read the serial port the gui is shown.

What is wrong here?

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{ 
    strVoltages << "Voltage 1" << "Voltage 2" << "Voltage 3";

    ui->setupUi(this);
    this->createLayout();

    this->readValues();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::readValues() {
    QSerialPort port;
    port.setPortName("COM3");
    port.setBaudRate(115200);
    port.setDataBits(QSerialPort::Data8);
    port.setParity(QSerialPort::NoParity);
    port.setStopBits(QSerialPort::OneStop);
    port.setFlowControl(QSerialPort::NoFlowControl);

    if (!port.open(QSerialPort::ReadWrite)) {
        qDebug() << "Error opening serial port: " << port.errorString() << endl;
    }
    else {
        while(1) {
            while (!port.canReadLine())
                port.waitForReadyRead(-1);

            while (port.canReadLine()) {
                QString strIn(port.readLine());
                QStringList strList = strIn.split(',');

                if(strList.count() == strVoltages.length()) {
                    int iLCDCounter = 0;
                    foreach(QString strTmp, strList) {
                        lLCDNumber.at(iLCDCounter++)->display(strTmp);
                        qDebug() << strTmp;

                    }
                }
            }
        }
    }
}

void MainWindow::createLayout() {

    QVBoxLayout * vBoxLayout = new QVBoxLayout();

    for(int iItr = 0; iItr < strVoltages.length(); iItr++) {
        lDescription.append(new QLabel(strVoltages.at(iItr)));
        lLCDNumber.append(new QLCDNumber());

        QHBoxLayout *hBoxLayout = new QHBoxLayout();
        hBoxLayout->addWidget(lDescription.last());
        hBoxLayout->addWidget(lLCDNumber.last());

        vBoxLayout->addLayout(hBoxLayout);
    }

    QWidget *w = new QWidget();
    w->setLayout(vBoxLayout);

    setCentralWidget(w);
}

Thanks!

[JonB]

@LeoC said in main window doesn't open although program is running:

while(1) {

That loop never exits.

Your code/GUI might be better written using signals for reading the data instead of waitForReadyRead() etc. Get the main window up & showing without waiting, and display the values as & when they arrive via signals/slots.

[arsinte_andrei]

why do you use while(1)??? have you heard of signal and slot?? use it!!

while(1) is useful for programming microcontrollers .. In Qt we use signal and slots

[Pablo J. Rogina]

@LeoC said in main window doesn't open although program is running:

What is wrong here?

It looks like the while() loop... You are supposed to work with signals & slots in Qt.

You may want to look at this example for serial terminal. I guess you'll grasp a good idea about how to work with the serial port

[LeoC]

Sorry for my late response.

It isn't the first time I use Qt and I heard about signals and slots of course. In this case I needed a very fast (and maybe dirty) solution so that I just copied 'something' from the internet. Shouldn't do this again. After you gave me the right hint I abandoned the above solution (since it didn't worked anyway) and started from scratch again. Not it works as it should do.

If someone is interested:

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{ 
    strVoltages << "Voltage 1" << "Voltage 2" << "Voltage 3";
    iMinSize = (3 * strVoltages.count() + strVoltages.count() - 1);
    iMaxSize = (4 * strVoltages.count() + strVoltages.count() - 1);
    bInvokedFirstTime = false;
    bInvokedSecondTime = false;

    ui->setupUi(this);
    this->setWindowTitle("Voltmeter");

    connect(&port,SIGNAL(readyRead()),this,SLOT(readValues()));

    this->createLayout();

    this->configureSerialPort();
    this->readValues();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::configureSerialPort() {
    port.setPortName("COM3");
    port.setBaudRate(115200);
    port.setDataBits(QSerialPort::Data8);
    port.setParity(QSerialPort::NoParity);
    port.setStopBits(QSerialPort::OneStop);
    port.setFlowControl(QSerialPort::NoFlowControl);

    if (!port.open(QSerialPort::ReadWrite)) {
        qDebug() << "Error opening serial port: " << port.errorString() << endl;
    }
    else
        qDebug() << "Serial port is ready";
}

void MainWindow::displayValues(QByteArray baTmp) {
    
    QStringList strListValues = QString(baTmp).split(",");

    int iLoopCounter = 0;
    foreach(QString strTmp, strListValues) {
        lLCDNumber.at(iLoopCounter)->display(strTmp);

        bool bCheck;
        double dNumber = strTmp.toDouble(&bCheck);

        if(dNumber < 10)
            lIndicator.at(iLoopCounter)->setStyleSheet("QLabel { background-color : red; }");

        iLoopCounter++;
    }
}

void MainWindow::readValues() {

    if(bInvokedFirstTime) {
        baDataIn.append(port.readAll());

        if(!bInvokedSecondTime) {
            int iPosOfExlM = baDataIn.indexOf("!");
            if(iPosOfExlM < iMinSize) {
                baDataIn = baDataIn.right(baDataIn.length() - (iPosOfExlM+1));
                bInvokedSecondTime = true;
            }
        }

        int iLengthOfDataIn;
        while(baDataIn.length() > iMaxSize) {
            int iPosOfExlM = baDataIn.indexOf("!");
            QByteArray baTmp;

            if(iPosOfExlM != -1) {
                baTmp = baDataIn.left(iPosOfExlM);
                baDataIn = baDataIn.right(baDataIn.length() - (iPosOfExlM+1));
                iLengthOfDataIn = baDataIn.length();

                if(baTmp.length() >= iMinSize && baTmp.length() <= iMaxSize) {
                    this->displayValues(baTmp);
                }
            }
        }
    }
    if(!bInvokedFirstTime) {
        bInvokedFirstTime = true;
        QByteArray baTmp = port.readAll();
    }
}

void MainWindow::createLayout() {

    QVBoxLayout * vBoxLayout = new QVBoxLayout();
    QFont f( "Arial", 30, QFont::Bold);

    for(int iItr = 0; iItr < strVoltages.length(); iItr++) {
        lDescription.append(new QLabel(strVoltages.at(iItr)));
        lDescription.last()->setFont(f);
        lDescription.last()->setFixedWidth(200);

        lLCDNumber.append(new QLCDNumber());
        lLCDNumber.last()->setFixedHeight(100);

        lIndicator.append(new QLabel());
        lIndicator.last()->setFixedWidth(100);
        lIndicator.last()->setFixedHeight(100);
        lIndicator.last()->setStyleSheet("QLabel { background-color : grey; }");

        QHBoxLayout *hBoxLayout = new QHBoxLayout();
        hBoxLayout->addWidget(lDescription.last());
        hBoxLayout->addWidget(lLCDNumber.last());
        hBoxLayout->addWidget(lIndicator.last());

        vBoxLayout->addLayout(hBoxLayout);
    }

    QPushButton *bReset = new QPushButton("Reset");
    vBoxLayout->addWidget(bReset);
    connect(bReset,SIGNAL(pressed()),this,SLOT(resetMeasurement()));

    QWidget *w = new QWidget();
    w->setLayout(vBoxLayout);

    setCentralWidget(w);
}

void MainWindow::resetMeasurement() {
    foreach(QLabel *lTmp, lIndicator) {
        lTmp->setStyleSheet("QLabel { background-color : grey; }");
    }
}

[arsinte_andrei]

if is working please mark this as solved from the menu... Many thanks