QByteArray to Double in Qt C++ 5.8.0 - c++

Question

I have a serial comport data read write program. Data is being read from the comport 4 (Eg: 1022), but when I'm trying to do a mathematical calculation of the data 1022/2 then its give me output as 0.5 5.0 51.00 511.0 means its not taking the whole 1022 as a single number for the mathematical calculation. Its take 1 first then divide 1/2=0.5 then once 0 digit receive it take as 10/2=5 and so on. But I want 1022 as a single digit number like (eg: 1022/2=511)
I have tried to convert the QByteArray into Double for the calculation.
void MainWindow::readData()
{
QByteArray data = serial->readAll();
bool ok;
QByteArray cata= QByteArray::number(data.toDouble(&ok)/2);
console->putData(cata);
}

Answer 1

So here an example of a TCP client/server in Qt. the server sends 1022.72, and the client receives it and shows the result value divided by 2. (run the server then the client:
Server Code:
test.pro:
#-------------------------------------------------
#
# Project created by QtCreator 2017-06-26T12:49:54
#
#-------------------------------------------------
QT += core gui network
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = test
TEMPLATE = app
# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS
# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
main.cpp:
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>
#include <QHostAddress>
#include <QAbstractSocket>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow),
_server(this)
{
ui->setupUi(this);
_server.listen(QHostAddress::Any, 4242);
connect(&_server, SIGNAL(newConnection()), this, SLOT(onNewConnection()));
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::onNewConnection()
{
QTcpSocket *clientSocket = _server.nextPendingConnection();
connect(clientSocket, SIGNAL(readyRead()), this, SLOT(onReadyRead()));
connect(clientSocket, SIGNAL(stateChanged(QAbstractSocket::SocketState)), this, SLOT(onSocketStateChanged(QAbstractSocket::SocketState)));
_sockets.push_back(clientSocket);
for (QTcpSocket* socket : _sockets) {
double data = 1022.72;
// socket->write(QByteArray::fromStdString(clientSocket->peerAddress().toString().toStdString() + " connected to server !\n"));
socket->write(QByteArray::fromStdString(QVariant(data).toString().toStdString()));
}
}
void MainWindow::onSocketStateChanged(QAbstractSocket::SocketState socketState)
{
if (socketState == QAbstractSocket::UnconnectedState)
{
QTcpSocket* sender = static_cast<QTcpSocket*>(QObject::sender());
_sockets.removeOne(sender);
}
}
void MainWindow::onReadyRead()
{
QTcpSocket* sender = static_cast<QTcpSocket*>(QObject::sender());
QByteArray datas = sender->readAll();
for (QTcpSocket* socket : _sockets) {
if (socket != sender)
socket->write(QByteArray::fromStdString(sender->peerAddress().toString().toStdString() + ": " + datas.toStdString()));
}
}
mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QTcpServer>
#include <QTcpSocket>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void onNewConnection();
void onSocketStateChanged(QAbstractSocket::SocketState socketState);
void onReadyRead();
private:
Ui::MainWindow *ui;
QTcpServer _server;
QList<QTcpSocket*> _sockets;
};
#endif // MAINWINDOW_H
mainwindow.ui: (empty)
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>400</width>
<height>300</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralWidget">
<layout class="QVBoxLayout" name="verticalLayout_2">
<item>
<layout class="QVBoxLayout" name="verticalLayout"/>
</item>
</layout>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>400</width>
<height>25</height>
</rect>
</property>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>
Client code:
test2.pro:
#-------------------------------------------------
#
# Project created by QtCreator 2017-06-26T14:34:11
#
#-------------------------------------------------
QT += core gui network
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = test2
TEMPLATE = app
# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS
# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
main.cpp:
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>
#include <QHostAddress>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow),
_socket(this)
{
ui->setupUi(this);
_socket.connectToHost(QHostAddress("127.0.0.1"), 4242);
connect(&_socket, SIGNAL(readyRead()), this, SLOT(onReadyRead()));
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::onReadyRead()
{
QByteArray datas = _socket.readAll();
qDebug() << QVariant(datas).toDouble() / 2;
ui->label->setText(QVariant(QVariant(datas).toDouble() / 2).toString());
_socket.write(QByteArray("ok !\n"));
}
mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QTcpSocket>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void onReadyRead();
private:
Ui::MainWindow *ui;
QTcpSocket _socket;
};
#endif // MAINWINDOW_H
mainwindow.ui: (result written here and also with qDebug)
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>400</width>
<height>300</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralWidget">
<layout class="QVBoxLayout" name="verticalLayout_2">
<item>
<layout class="QVBoxLayout" name="verticalLayout">
<item>
<widget class="QLabel" name="label">
<property name="text">
<string/>
</property>
</widget>
</item>
</layout>
</item>
</layout>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>400</width>
<height>25</height>
</rect>
</property>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>