QProgressBar "crash" - doesn't work properly

I'm usign a QProgressBar to know the state of a job that consist in read a file.
My problem is if during that process i click in anything or open anothers aplications, my aplication act like it crashed and just show 100% when the process finish, like: 1%, 2%, i click, ------------------ 100%.
If i just run and didn't do nothing in my pc the QProgressBar show the process correct, like, 1%, 2%, 3%, 4%, ..., 99%, 100%.

Code:

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#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QtGui/QMainWindow>
#include <QProgressBar>
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
public slots:
    void test();
 
private:
    QProgressBar *progress;
};
 
#endif // MAINWINDOW_H

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Code:

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#include "mainwindow.h"
#include <QDebug>
#include <QString>
#include <QDir>
#include <QFileDialog>
#include <QMessageBox>
#include <QLabel>
#include <QProgressBar>
#include <QLayout>
#include <QVBoxLayout>
#include <QTimer>
#include <QProgressDialog>
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
 
    QVBoxLayout *layout = new QVBoxLayout;
    progress = new QProgressBar;
    layout->addWidget(progress);
 
    QWidget *w=new QWidget();
    w->setLayout(layout);
    this->setCentralWidget(w);
 
    QTimer::singleShot(100, this, SLOT(test()));
}
 
MainWindow::~MainWindow()
{
 
}
 
void MainWindow::test(){
    QString dir = QFileDialog::getOpenFileName(this, tr("Select Text File"),"",tr("Text (*.txt)"));
    QFile f(dir);
    f.open(QIODevice::ReadOnly);
    if(f.isOpen())
    {
        int fileSize=f.size();
        int step=fileSize/100;
        int bytesProcessed=0;
        QString line;
        QStringList list;
        progress->setMaximum(fileSize);
        progress->setValue(bytesProcessed);
        while (not f.atEnd()){
            line = f.readLine().data();
            bytesProcessed+= line.size();
            list = line.split(":");
            if (bytesProcessed%step<=20){
                //qDebug()<<"bytesProcessed:"<<bytesProcessed;
                progress->setValue(bytesProcessed);
            }
        }
        progress->setValue(bytesProcessed);
 
    }
    else
    {
        QMessageBox::warning(this,"Error","No file selected!");
    }
}

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To be honest I'm suprised that if you don't do anything then it works correctly. You have a while loop that doesn't allow events to be processed so the progress bar shouldn't get updated. At least add a QCoreApplication::processEvents() call after each call to QProgressBar::setValue().

It's work now even if i do another things :) Thanks :)

Quote:

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To be honest I'm suprised that if you don't do anything then it works correctly.

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It's true, i can record a video if you want to see :s

Quote:

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Originally Posted by metRo_

It's true

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Well, it shouldn't work.

Anyway, this "QCoreApplication::processEvents()" is the best way to do what i want or just an easy way?

It's an easy way. But for such a simple operation like this it is ok. If you start doing something besides reading from file then some other approach might be better. For this situation the only change I could advise would be to read the file using a thread so that the main part of the application can do other things while the data is being loaded.

In general read this: [wiki]Keeping the GUI Responsive[/wiki].

thanks, i'll read this.