Reading in from a streaming text file

jde08

Hi,

I'm trying to read in a line from an instrument that streams in data into a txt file in the format:

:SA, -1.05, -0.83,190.98
:TS,13050814070409,35.0,+22.4, 0.0,1528.0, 0
:BI,-32768,-32768,-32768,-32768,V
:BS,-32768,-32768,-32768,V
:BE,-32768,-32768,-32768,V
:BD, +0.00, +0.00, +0.00, 0.00, 0.00

I only need the three data points after the :SA and the first data point after :TS.

I wrote this in c++ using getline, but implementing it into Qt has proven above me.
I am brand new to Qt, have only been using it for 2 days and would really appreciate any pointers I could get.

mcosta

Hi,

you can use QTextStream::readLine() instead of getline().
Once you read a line you can choose one of

Use QTextStream to read items
QString::split() to split line in tokens

jde08

After the line is split with QString::split() how do I compare the values of the first list entry to check if its a line I could use.

Also after I split up the line how would I assign the values to labels?

mcosta

Hi,

QStringList is inherited from QList, so you can use operator [] to access to elements.

@
QStringList tokens = line.split (",");
if (tokens[0] == ":SA") {
// Do something
}
else if (tokens[0] == ":TS") {
// Do something
}
@

To assign text to labels you can use QLabel::setText()

jde08

Thanks for your help so far!

I have another question say the .txt file I want to read is located in C:\Program Files...

How would I route the program to that directory?

Here is the code I have written so far.
@ #include "mainwindow.h"
#include <QApplication>
#include <QGridLayout>
#include <QLabel>
#include <QtGui>
#include <iostream>
#include <stdio.h>
#include <QString>
#include <QStringList>
#include <QFile>
#include <QTextStream>
using namespace std;

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

QWidget w;

int roll;
int pitch;
int heading;
int i=1;                //counter for next entry
int filenum = 0;
int filenum1= filenum+1;
int n=0;                //counter for current entry

QString qstr1 = QString::number(roll);
QString qstr2 = QString::number(pitch);
QString qstr3 = QString::number(heading);
QString filename = QString("ADCP%1_000000").arg(filenum);
QString filename1 = QString("ADCP%1_000000").arg(filenum1);


QFile file&#40;filename1&#41;;
if (file.exists())              //Looks for newest ADCP file
{
    filenum++;                 //if ADCP+1 exists starts from that file     
}
else
{
   QFile file&#40;filename&#41;;
    if(i!=n)                //if counters don't match starts current counter at zero
    {                       //to read from start of the file and opens file.
        n=0;
        file.open(QIODevice::ReadOnly |QIODevice::Text);
    }
     if ( file.open(QIODevice::ReadOnly |QIODevice::Text) )
     {
         QTextStream in(&file);
         QString line = in.readline();            //reads and splits lines
         QStringList tokens = line.split (",");
         if (tokens[0] == ":SA")
         {
             n++;                       //increases current counter whenever :SA appears.
             if (n==i)                  //when current counter = next counter displays data
             {
                 qstr1= tokens[1];
                 qstr2= tokens[2];
                 qstr3= tokens[3];
             }

         }
     else if (tokens[0] == ":TS")
         {
             if (n==i)                  //Same as above and increases next counter for the next reading
             {
                 i++;
                 QString timestring = tokens[1];
             }
         }
       }
  }

QGridLayout* mainLayout = new QGridLayout(&w);
QLabel* rolllabel = new QLabel("Roll:   ");
QLabel* pitchlabel = new QLabel("Pitch:  ");
QLabel* headinglabel = new QLabel("Heading:  ");
QLabel* rollreading = new QLabel(qstr1);
QLabel* pitchreading = new QLabel(qstr2);
QLabel* headingreading = new QLabel(qstr3);

mainLayout->addWidget(rolllabel,0,0);               //Prints to gui
mainLayout->addWidget(rollreading,0,1);
mainLayout->addWidget(pitchlabel,1,0);
mainLayout->addWidget(pitchreading,1,1);
mainLayout->addWidget(headinglabel,2,0);
mainLayout->addWidget(headingreading,2,1);


w.show();

return a.exec&#40;&#41;;

}
@

mcosta

Hi,

what is the question?

Suggestion: Open New Thread for new Question

tobias.hunger

Provided your txt file is not static then the file should not be in C:\Program Files at all. The stuff there should not change after installation. You will also need elevated privileges just to write there.

jde08

The text file is written in the data folder of an instrument interface. That is why I'm trying to read from (not write) a C:\Program Files directory.

The question was how do I open a file in a certain directory. For me this is C:\Program Files\RD Instruments\VmDas\data\

tobias.hunger

Have you tried this?

@QString filename = QString("C:/Program Files/RD/Instruments/VmDas/data/ADCP%1_000000").arg(filenum);@

I still think that this is the wrong place for files like that;) %APPDATA% is where Microsoft intends application data to be stored.