Windows not responding on reading file from txt

deleted286

@mrjj I got it. Thank you so much it works. If I add a timer to code, cann it writes one line to the screen every 20 seconds

mrjj

@suslucoder
Hi
Well not directly with that code as we loop until all is added.

But you could do (pseudo code. didn't compile it)


 QStringList allLines; // this goes in .h as a class member
 int curIndex = 0; // this goes in .h as a class member

QFile inputFile(fileName);
if (inputFile.open(QIODevice::ReadOnly))
{
   QTextStream in(&inputFile);
   while (!in.atEnd())
   {
      QString line = in.readLine();
      allLines.append(line); // add to list 
   }
   inputFile.close();
}

    QTimer *timer = new timer(this);
    connect(timer, &QTimer::timeout, [this]() {
        QString line = allLines[curIndex]; // get a line from list
        ui -> plainTextEdit->setPlainText(line); // add the line
        if (curIndex < allLines.size() - 1 ) // if not at end of allLines 
            curIndex++; // raise index
    });
    timer->start(20000);

deleted286

@mrjj thank you so much

mrjj

@suslucoder
Np, i hope its not to much cheating if its an assignment :)

deleted286

@mrjj hahah im newly graduated from university, I want to improve myself in Qt. That's why I think of different scenarios to challenge myself.

mrjj

@suslucoder
Oh all good then. :)
Thats a good idea as one mostly get better at coding, by coding.

deleted286

@mrjj I didnt understand the idea behind --> connect(timer, &QTimer::timeout, this

Cant we do this using signal and slot?

There is an error like expected body of lambda expression

deleted286

@mrjj Hey, i got ASSERT failure in QList<T>::operator[]: "index out of range" ERROR. I cannot understand why. Can you help me?

mrjj

@suslucoder
hi
its means you try to access some index in a list and that index is too big.
I would guess on curIndex if it gets bigger than the allLines.size()
or if allLines is empty.
Did you load the file to the list before starting the timer ?

its a lambda, yes, but you can also use a normal slot to do the same.

deleted286

@mrjj ``` I couldnt find my mistake :(

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFile>
#include <QTextStream>
#include <QMessageBox>
#include <QTimer>
#include <QList>
#include <qlist.h>
#include <QDebug>


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

    QTimer *timer = new QTimer(this);

    connect(timer, SIGNAL(timeout()), SLOT(on_pushButton_clicked()));

    QString line = allLines[curIndex];
    ui->plainTextEdit->setPlainText(line);
    if(curIndex < allLines.size() - 1 ) {
        curIndex++;
    }
    
    
    timer->start(20000);
    
}
MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_pushButton_2_clicked()  //write
{
    QFile file("C:/Users/ilknu/Documents/QFileDemo/abc.txt");
    if(!file.open(QFile::WriteOnly | QFile::Text )) {

        QMessageBox::warning(this, "title", "file not open");


    }

    QTextStream out (&file);
    QString text = ui->plainTextEdit->toPlainText();
    out << text;
    file.flush();
    file.close();


}

void MainWindow::on_pushButton_clicked()  //read
{

    QFile file("C:/Users/ilknu/Documents/QFileDemo/abc.txt");

    // QMessageBox::warning(this, "title", "file not open");
    // QTextStream in (&file);
    //    while (!in.atEnd()) {
    //        QString text = in.readLine();
    //    }

    //QString text = in.readLine();

  if(file.open(QIODevice::ReadOnly)) {
      QTextStream in (&file);
      while (!in.atEnd()) {

         // QString line = in.readLine();
         //  ui -> plainTextEdit->setPlainText(all);

 QString line = in.readLine();
 allLines.append(line);
 
          }
 }


      file.close();  }

  //  file.close();

mrjj

Hi
Well

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

QTimer *timer = new QTimer(this);

connect(timer, SIGNAL(timeout()), SLOT(on_pushButton_clicked()));

/// all this should be in the slot -> on_pushButton_clicked if that how you load it

QString line = allLines[curIndex]; /// this will CRASH as you didnt fill list yet
ui->plainTextEdit->setPlainText(line);
if(curIndex < allLines.size() - 1 ) {
curIndex++;
}

timer->start(20000);  /// do not start timer before you have loaded into list..

So it was mostly the order of the code

deleted286

@mrjj im so confused about the order of my code. I tried all combinations that come to my mind, but when i clicked the read button my application was ended forcefully :(

mrjj

@suslucoder
Ok
You want it like

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

    QTimer *timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), SLOT(Timer_Slot()));   // NOTE  new slot for timer    
}

// new slot for timer..  also put in .h under public slots:
void MainWindow::Timer_Slot() {
    QString line = allLines[curIndex];
    ui->plainTextEdit->setPlainText(line);
    if (curIndex < allLines.size() - 1 ) {
        curIndex++;
    }    
}

void MainWindow::on_pushButton_clicked()  //read
{

    QFile file("C:/Users/ilknu/Documents/QFileDemo/abc.txt");
    if (file.open(QIODevice::ReadOnly)) {
        QTextStream in (&file);
        while (!in.atEnd()) {
            QString line = in.readLine();
            allLines.append(line);

        }
    }
    file.close();
    curIndex=0; // make sure we start from start
    timer->start(20000); // we have read the lines, start timer
}

deleted286

@mrjj It works. Thank you for your help.

Pablo J. Rogina

@suslucoder said in Windows not responding on reading file from txt:

It works

so please don't forget to mark your post as solved!