I got the answer.

QDir directory = QFileDialog::getExistingDirectory(this, tr("Open Directory"),"/home", QFileDialog::ShowDirsOnly| QFileDialog::DontResolveSymlinks); auto listWidget_images = new QListWidget();//set listwidget to display images listWidget_images->setMinimumSize(1200,400); listWidget_images->setViewMode(QListWidget::IconMode); listWidget_images->setIconSize(QSize(320,240)); listWidget_images->setResizeMode(QListWidget::Adjust); for(const QFileInfo & finfo: directory.entryInfoList()){ ui->listWidget_dirs->addItem(finfo.absoluteFilePath()); } connect(ui->listWidget_dirs, & QListWidget::itemClicked,[listWidget_images,this](QListWidgetItem *item) { listWidget_images->show(); listWidget_images->clear(); QDir directory(item->text()); directory.setNameFilters({"*.png", "*.jpg"}); for(const QFileInfo & finfo: directory.entryInfoList()){ QListWidgetItem *item = new QListWidgetItem(QIcon(finfo.absoluteFilePath()), finfo.fileName()); listWidget_images->addItem(item); } });

@aha_1980
It works ! Thanks alot
:)

@Chris-Kawa @mrjj
sorry for the late reply,
thanks guys it now works using setnotifyinterval() :)

@mjsurette
With the important note:

Notice that random devices may not always be available to produce random numbers (and in some systems, they may even never be available). This is signaled by throwing an exception derived from the standard exception on construction or when a number is requested with operator().
Unless the program really requires a stochastic process to generate random numbers, a portable program is encouraged to use an alternate pseudo-random number generator engine instead, or at least provide a recovery method for such exceptions.

Windows will not provide real random numbers (at least to my knowledge), and in Linux this is implementation dependent. Even if /dev/random is advertised to produce real random numbers, the truthfulness of such a statement is debatable. Often enough the random device just generates a pseudo-random sequence. That's why you get the above note on portability.

Kind regards.

@Lorence said:

Hi when you add "xxxx" to a qlistwidget
you are adding a QListWidgetItem.

While you can subclass QListWidgetItem and make your own
that has signals, it would not do you so much good as

it would never never emit such signal unless you also made it do
so when something happen to it. (overriding some of its functions)

So It all depends what you are trying to do.
If you just want to know its no 1,2,3 etc, even if moved
then
you can insert that info into the QListWidgetItem using the
void QListWidgetItem::setData(int role, const QVariant & value)

something like
QListWidgetItem * item=new QListWidgetItem("item1") ;
item->setData(Qt::UserRole, 1); // or 2 for item 2 etc
list->addItem(item)

then you can always know which is which even if rearranged.
see here for how to take index out also
http://stackoverflow.com/questions/7136818/can-i-store-some-user-data-in-every-item-of-a-qlistwidget

@TheBadger
I tried to investigate the error, and i found where it is coming from
its from this line
playList.emplace_back(ui->song->text().toStdString());
which is written before the connect() in the code

@maximo Did you finally submit an app to the Mac App store and which web incarnation of Qt did you use ?

There's no multi-threading involved here whatsoever. All code here runs in a single thread (unless the timer object and "this" actually live in different threads).

There's an event loop running in your app and timer events are just the same as any other. They get put in a queue and processed one after another.
The above will basically mean that your slot is run every time Qt processes messages. It can have very bad influence on your app responsiveness if what you do in the slot is heavy.

The most obvious question is: if you want a thread why not use an actual QThread instead of emulating it like that?

Here's an example of the errors I got.
http://hastebin.com/qalutirici.coffee

This seems like a false positive or something that isn't in my code (maybe I'm wrong).
In each error I got, the "at" is pointing to a function that isn't part of my code.