CODEWITHSUNDEEP
qtwindowshow
madasionka
madasionka

Reputation: 922

Qt: How to list hidden windows?

I am trying to show() a hidden MainWindow from my main.cpp (in fact all windows are hidden at this point). I tried doing something like this:

QList<QWindow*> windows = QApplication::allWindows();
for (int i = 0; i < windows.size(); ++i) {
    if (windows.at(i)->objectName() == "MainWindow")
        windows.at(i)->show();
}

But it doesn't work.

In Qt documentation in QApplication::allWidgets() there is an annotation :

Note: Some of the widgets may be hidden.

As if this function wasn't listing hidden widgets and I suppose that's the same case with allWindows(), because I tested this piece of code when windows are not hidden and it worked.

Basically in the void MainWindow::closeEvent function I do:

    event->ignore();
    hide();

And then I want to be able to reopen the MainWindow when I click on the application's icon.

Does anyone have a better idea how to show a hidden window from main.cpp or can indicate if I am doing something wrong?

edit: this probably works, my issue lied somewhere totally different.

Upvotes: 0

Views: 743

Answers (1)

phyatt
phyatt

Reputation: 19122

The method for finding all of a particular kind of window in the Qt Object tree can be shortened:

http://doc.qt.io/qt-5/qobject.html#findChildren

QList <QMainWindow *> mainWindows = qApp->findChildren<QMainWindow *>();
foreach(QMainWindow * w, mainWindows)
{
    qDebug() << "Found a main window" << w->objectName() 
        << "isVisible?" << w->isVisible();
}

http://doc.qt.io/qt-5/qobject.html#findChild

Or if you know the name of the qobject:

QMainWindow * w = qApp->findChild<QMainWindow *>("My Named MainWindow");
if(w)
{
    qDebug() << "Found" << w->objectName() << "isVisible?" << w->isVisible();
}

findChild and findChildren can be used on any QObject or a subclass of QObject, and can be used to reflect out a pointer to any of their children.

MyMainWindow * w = qApp->findChild<MyMainWindow *>();

Also if you want any QWidget to not die or close the application if it is the last window to be closed, then use: 

w->setAttribute(Qt::WA_DeleteOnClose, false);

http://doc.qt.io/qt-5/qguiapplication.html#quitOnLastWindowClosed-prop

qApp->setQuitOnLastWindowClosed(false);

but then you have to explicitly put qApp->close() somewhere in your code.

Another related tool to all of this is qobject_cast; I like using it with QObject::sender();

// some slot connected to by multiple sources
void mySlot()
{
    QPushButton * b = qobject_cast<QPushButton *>(QObject::sender());
    if(b)
    {
       qDebug() << "Push Button triggered" << Q_FUNC_INFO;
       b->setText("Ouch");
       b->setDisabled(true);
    }
}

Hope that helps.

Upvotes: 1

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