Use Json data in Qt in Windows

[Christian Ehrlicher]

I don't see a difference between those two pictures. The json content is exactly the same. If you want to parse the json you should take a look at the documentation of QJsonDocument and it's corresponding classes.

[Negar_mg]

@Christian-Ehrlicher
Thanks, how can I separate the data? I do not know how to use QJsonDocument?
Can you guide me with an example? For example, what should I do to store the amount of Bat_Temp data in the x variable?

[mrjj]

@Negar_mg said in Use Json data in Qt in Windows:

QJsonDocument

   QString input = "{Bat_temp:19}"; // you used a picture so could not get real input
  // the toUTF is due to it wants a bytearrya not qstring. 
   QJsonDocument jsonResponse = QJsonDocument::fromJson(input.toUtf8());
  // ask for a json object
    QJsonObject jsonObject = jsonResponse.object();
  //access a property of that json object
    int value = jsonObject["Bat_temp"].toInt();

for dht11Data you must use QJsonArray

[Negar_mg]

@mrjj
thank you

[_-mohamed-_]

@Negar_mg this is the best example, it helped me a lot:
Example of how to use JSON file with QT

[Negar_mg]

@_-mohamed-_
thanks a lot
You know, my problem is that I receive data from the Arduino from the serial port
As I wrote in the above code, I can print data with an infinite loop.
As follows :

            while (true)
            {
            serial.waitForReadyRead (100000);
            input = input.append (serial.readAll ());
            qDebug () << input;
            }

And the output is as follows:

//..............................................................................................................................
Serial is open
"{"
"{" dht "
"{" dht11Da "
"{" dht11Data \ ":"
"{" dht11Data \ ": [29,"
"{" dht11Data \ ": [29,27]}"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " "
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht1 "
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Da "
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Data \ ":"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Data \ ": [\ r \ n"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Data \ ": [\ r \ n"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Data \ ": [\ r \ n 29, \ r"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Data \ ": [\ r \ n 29, \ r \ n"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Data \ ": [\ r \ n 29, \ r \ n 27 \ r"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Data \ ": [\ r \ n 29, \ r \ n 27 \ r \ n]"
"{" dht11Data \ ": [29,27]} \ r \ n {\ r \ n " dht11Data \ ": [\ r \ n 29, \ r \ n 27 \ r \ n] \ r \ n } "
//..........................................................................................................................................
No data is received at first, so I do not know how to manage this infinite loop and store the data in an array

[_-mohamed-_]

@Negar_mg do you mean that you want to save the final result in a json file?

[Negar_mg]

@_-mohamed-_
i want to save this {" dht11Data \ ": [29,27]}
And I want to display each of the numbers like 27 in one lineEdit.

[_-mohamed-_]

@Negar_mg You can't use a backslash in the key, you can use FrontSlash instead

This is the code you need:

#include <QApplication>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QByteArray>
#include <QJsonValue>
#include <QDebug>
#include <QFile>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QFile file("C:/Users/moham/OneDrive/Desktop/json file.json"); //write the file path here

    if(!file.open(QFile::ReadOnly))    //opening file
        qDebug() << "can't open the file";

    else
    {
        QByteArray fileContents = file.readAll(); // reading the file
        file.close();   //closing file

        QJsonDocument jsonDoc = QJsonDocument::fromJson(fileContents);

        QJsonObject jsonObj = jsonDoc.object();

        QJsonArray jsonArray = jsonObj[" dht11Data / "].toArray();

        foreach(QJsonValue v, jsonArray)  //printing array's values
            qDebug() << v.toInt();        //

        return 0;
    }

    return a.exec();
}

this code reads (JSON file.json) and prints it in the console, you can use the values wherever you want.

I hope I helped you.

[jsulm]

@Negar_mg said in Use Json data in Qt in Windows:

infinite loop

Stop using infinite loops first!
Please take a look at documentation and examples to see how to properly use QSerialPort: https://doc.qt.io/qt-5/qtserialport-creaderasync-example.html
To read from serial port connect a slot to https://doc.qt.io/qt-5/qiodevice.html#readyRead signal and use readAll() in this slot. Keep in mind that you have to accumulate the data read from serial port until you got whole JSON document!

[Negar_mg]

Thank you all

[Negar_mg]

I finally succeeded,The code I wrote is as follows:

 MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
  {
ui->setupUi(this);

   m_serialPort=new QSerialPort;
   m_serialPort->setPortName("COM3");

   m_serialPort->open(QIODevice::ReadWrite);
   m_serialPort->setBaudRate(QSerialPort::Baud9600);
   m_serialPort->setDataBits(QSerialPort::Data8);
   m_serialPort->setParity(QSerialPort::NoParity);
   m_serialPort->setStopBits(QSerialPort::OneStop);
   m_serialPort->setFlowControl(QSerialPort::NoFlowControl);
    while(!m_serialPort->isOpen()) m_serialPort->open(QIODevice::ReadWrite);

    connect(m_serialPort, &QSerialPort::readyRead, this, &MainWindow::handleReadyRead);
    connect(&m_timer, &QTimer::timeout, this, &MainWindow::handleTimeout);

    m_timer.start(5000);
 }


       void MainWindow::handleReadyRead()
      {
   m_readData.append(m_serialPort->readAll());

if (!m_timer.isActive())
    m_timer.start(5000);
  }

    void MainWindow::handleTimeout()
 {
if (m_readData.isEmpty()) {
    qDebug()<< "m_readData is empty" <<m_readData;

} else {


    qDebug()<< "m_readData is full" <<m_readData;




    QJsonDocument jsonDoc = QJsonDocument::fromJson(m_readData);
    QJsonObject jsonObj = jsonDoc.object();

    QJsonValue jsonVal;
    jsonVal = jsonObj.value(QString("Bat_Temp"));
    QTextStream textStream(stdout);
    textStream << QString::number(jsonVal.toInt()) << endl;
}