UI isn't shown when worker thread runs.

[Zola]

I have one worker thread which parses XML and passing QString parsed data via signal to QLabel slot setText();

I create thread and xmlparse class instances that runs in my MainWindow constructor like this:

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

What can cause situation that my UI with label does not appear when application is launched?

[SGaist]

Hi,

Are you sure that startParsing doesn't block the main thread ?

[Zola]

@SGaist

Here is my mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <xmlparser.h>
#include <QThread>

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

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::startParsing()
{
    QThread *xml = new QThread;
    xmlparser *first = new xmlparser();

    first->moveToThread(xml);
    xml->start();

    connect(first, SIGNAL(xmlParsed(QString)), ui->label, SLOT(setText(QString)));
}

[SGaist]

Ok then, are you sure that your label is not just empty rather than not visible ?

Note that you have two memory leaks here.

[JKSH]

@Zola said:

What can cause situation that my UI with label does not appear when application is launched?

Did you call MainWindow::show()?

[Zola]

@JKSH @SGaist

It is shown in main.cpp with:

MainWindow w;
w.show();

[SGaist]

Did you check that xmlparser correctly emits xmlParsed and that the parameter is not empty ?

[Zola]

I solved my problem with not calling parseFunction in its own class constructor but with signals and slots in mainwindow.cpp file:

connect(xml, SIGNAL(started()), first, SLOT(parseFunction()));