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Forum Update on Monday, May 27th 2025

Windows not responding on reading file from txt

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file readqt creatorqfile
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  • mrjjM mrjj

    @suslucoder

    hi
    it does read all of the files but if you do
    ui -> plainTextEdit->setPlainText(line);
    you then replace all text with the line you just read, over and over. so it only show the last line in the end.

    so you want to do

    ui -> plainTextEdit->appendPlainText(line);

    https://doc.qt.io/qt-5/qplaintextedit.html#appendPlainText

    to add the lines as you read them.

    ps. you dont have to read it line by line if all you want is to read it all and put in plainText.
    https://doc.qt.io/qt-5/qtextstream.html#readAll

    QFile inputFile(fileName);
    if (inputFile.open(QIODevice::ReadOnly))
    {
      QTextStream in(&inputFile);
      QString all = in.readAll();
      ui -> plainTextEdit->setPlainText(all);
    }
    
    D Offline
    D Offline
    deleted286
    wrote on last edited by
    #7

    @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

    mrjjM 1 Reply Last reply
    0
    • D 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

      mrjjM Offline
      mrjjM Offline
      mrjj
      Lifetime Qt Champion
      wrote on last edited by mrjj
      #8

      @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);
      
      
      
      
      
      
      D 1 Reply Last reply
      1
      • mrjjM 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);
        
        
        
        
        
        
        D Offline
        D Offline
        deleted286
        wrote on last edited by
        #9

        @mrjj thank you so much

        mrjjM 1 Reply Last reply
        0
        • D deleted286

          @mrjj thank you so much

          mrjjM Offline
          mrjjM Offline
          mrjj
          Lifetime Qt Champion
          wrote on last edited by
          #10

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

          D 1 Reply Last reply
          0
          • mrjjM mrjj

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

            D Offline
            D Offline
            deleted286
            wrote on last edited by
            #11

            @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.

            mrjjM 1 Reply Last reply
            0
            • D 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.

              mrjjM Offline
              mrjjM Offline
              mrjj
              Lifetime Qt Champion
              wrote on last edited by
              #12

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

              D 1 Reply Last reply
              0
              • mrjjM mrjj

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

                D Offline
                D Offline
                deleted286
                wrote on last edited by
                #13

                @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

                D 1 Reply Last reply
                0
                • D 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

                  D Offline
                  D Offline
                  deleted286
                  wrote on last edited by
                  #14

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

                  mrjjM 1 Reply Last reply
                  0
                  • D deleted286

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

                    mrjjM Offline
                    mrjjM Offline
                    mrjj
                    Lifetime Qt Champion
                    wrote on last edited by mrjj
                    #15

                    @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.

                    D 1 Reply Last reply
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                    • mrjjM 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.

                      D Offline
                      D Offline
                      deleted286
                      wrote on last edited by
                      #16

                      @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();
                      
                      mrjjM 1 Reply Last reply
                      0
                      • D 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();
                        
                        mrjjM Offline
                        mrjjM Offline
                        mrjj
                        Lifetime Qt Champion
                        wrote on last edited by mrjj
                        #17

                        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

                        D 1 Reply Last reply
                        0
                        • mrjjM 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

                          D Offline
                          D Offline
                          deleted286
                          wrote on last edited by
                          #18

                          @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 :(

                          mrjjM 1 Reply Last reply
                          0
                          • D 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 :(

                            mrjjM Offline
                            mrjjM Offline
                            mrjj
                            Lifetime Qt Champion
                            wrote on last edited by mrjj
                            #19

                            @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
                            }
                            
                            
                            D 1 Reply Last reply
                            1
                            • mrjjM 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
                              }
                              
                              
                              D Offline
                              D Offline
                              deleted286
                              wrote on last edited by
                              #20

                              @mrjj It works. Thank you for your help.

                              Pablo J. RoginaP 1 Reply Last reply
                              0
                              • D deleted286

                                @mrjj It works. Thank you for your help.

                                Pablo J. RoginaP Offline
                                Pablo J. RoginaP Offline
                                Pablo J. Rogina
                                wrote on last edited by
                                #21

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

                                It works

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

                                Upvote the answer(s) that helped you solve the issue
                                Use "Topic Tools" button to mark your post as Solved
                                Add screenshots via postimage.org
                                Don't ask support requests via chat/PM. Please use the forum so others can benefit from the solution in the future

                                1 Reply Last reply
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