Hi, This will depend on your widgets and what their content. It will also depend on the device that runs your application. But more seriously, unless you are under very high memory constraints you should allocate the widgets commonly used from the start and the ones that are less often used when they are needed.

@newToQt26 Hi Good to hear. :) If the user can add or delete layers, it's pretty important you make sure curScene/curView always points to something valid as else you get a nasty crash.

@hobbyProgrammer I don't know what is going on here, but I note that for a given circuitID you do two new Circuit(circuitID)s, one in fillCircuitMenu() and another any time slot goToCircuit(int index) is invoked. I don't know if that is correct, no re-use of same Circuit instance? Separately, I don't think there is any need to use deprecated QSignalMapper any longer. You can replace with new signal/slot syntax (you should get away from SIGNAL/SLOT() macros in all new code) plus a lambda. See e.g. https://doc.qt.io/qt-5/qsignalmapper.html#details for an example of this.

@hobbyProgrammer Do you actually have event loop running when you emit the signal?

Because this is getting out of hand: https://github.com/DeiVadder/LoginExample

Hi, You don't call show on your sw object and it's not part of your stacked widget.

You're correct and that's a good question. What version of Designer are you using ?

Hi Main windows is a bit special since it has "central widget". which there to allow to define areas around it for Dock windows. That is why we insert widget first. For all types of other widget we would insert directly. QWidget* centralWidget = new QWidget(); QVBoxLayout *layout = new QVBoxLayout; centralWidget->setLayout(layout); layout->addWidget(st); setCentralWidget(centralWidget); seems fine. For centralWidget , u can then use the Stacked. My mainWindow code actually looks like: MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow) { setLayout(layout); // that sets directly on mainwin. not sure it does what we think. You can just single step and see the values to find out why u crash. Sorry, i cant spot it. Running it helps. I think u need a setCentral also. That is the reason no 2 to why i like UI file so much. no crashing as u can only insert legally when visually :) And no code to try to spot bugs in. I think u need new widget widget as central new layout layout to widget inset stacked to that layout and then the page stuff

Hi, Since you marked it solved, can you share what you did to fix your code ?

@mrjj Hi! I managed to make everything just as I wanted, everything is going fine. The code example you sent me really did the trick. Thanks a lot.

Hi, Silly short answer but: yes it is

@raven-worx Hello, Thanks for the code, but I know how to do the scheduling. I actually went with QPointer<QObject> since the QObject might be deleted while waiting in the event loop. Like this: bool AgDial::eventFilter(QObject * object, QEvent * event) { switch (event->type()) { case QEvent::ChildAdded: QMetaObject::invokeMethod(this, "scheduleChildAdd", Qt::QueuedConnection, Q_ARG(QPointer<QObject>, QPointer<QObject>(reinterpret_cast<QChildEvent *>(event)->child()))); break; case QEvent::ChildRemoved: d()->detachAction(reinterpret_cast<QChildEvent *>(event)->child()); break; } return QStackedWidget::eventFilter(object, event); } Thanks for taking the time though! Kind regards.

@WhatIf Hi Yes it was as i thought of. Even better actually as you found singleShot :) Only thing that I wondered was the singleShot(200) as 200 is very fast :)

Hi yes its normal. You set the active page in Designer when you go to it. You can call ui->yourstackedwidget->setCurrentIndex(0) in QMainWindow constructor to make sure first page is always displayed.

@AlaaM Well , i did see it but button start in 0,0 perfect valid so did not think much about it. Just added + QString::number(i) so when testing by changing stackedWidget->setCurrentIndex(0); I could see it was indeed another button :)

My first thought is that QGroupBox probably provides a sizehint() that is zero if the widget is not visible where your other widget probably does not do this. The QStackedWidget would provide a sizehint() based on all of the children. When you hide the children you make the end result no smaller than the largest child. Another idea to implement this is to have a common set of options always visible and show/hide the additional parts that are unique to the 'multi' and 'other' views. This will autosize.

Hi and welcome While using QStackedWidget for all pages / screens could work just fine, a more common design would/could be using QDialog for welcome and login and when closed - the main window for the graphs etc.

In case anyone wonders, I found the way to connect both classes and tell mainWidget to change stack through the login widget's button. //header of the login widget public slots: void verifyUser(int iUserCorrect ) { if ( iUserCorrect != iUserVerified ) { iUserVerified = iUserCorrect; emit valueChanged( iUserVerified ); } } signals: void valueChanged( int iUserCorrect ); private slots: void on_btnLogin_clicked(); private: Ui::QLogin *ui; QSqlDatabase sqlUsuarios; int iUserVerified; source file of the login widget (only where valueChanged was used, in the SQLite verification): iUserVerified = 0; QSqlQuery sqlQry; if(sqlQry.exec("SELECT User, Password, Role FROM Usuarios WHERE User=\'" + sUsername + "\' AND Password =\'" + sPassword + "\'")) { if(sqlQry.next()) { ui->lblStatus->setText("Nombre de usuario y contraseña válidos."); qDebug() << "Usuario OK"; verifyUser(1); } and finally, the connect() in the mainWidget source file. Note that I had already made an instance of a promoted login widget inside this file: #include "mainwidget.h" #include "ui_mainwidget.h" #include <qlogin.h> #include <QMessageBox> #include <QCalendarWidget> #include <QDebug> #include <QPushButton> mainWidget::mainWidget(QWidget *parent) : QWidget(parent), ui(new Ui::mainWidget) { mainLayout = new QVBoxLayout(); stackedLayout = new QStackedLayout(); QLogin *loginWidget = new QLogin; stackedLayout->addWidget(loginWidget); stackedLayout->addWidget(new QCalendarWidget); mainLayout->addLayout(stackedLayout); setLayout(mainLayout); connect(loginWidget, SIGNAL(valueChanged(int)), this, SLOT(changeStack())); ui->setupUi(this); } The changeStack method simply changes the index of the stack: void mainWidget::changeStack() { stackedLayout->setCurrentIndex(stackedLayout->currentIndex() + 1); qDebug() << "changeStack()"; } Took me some time, but I finally got it.

It really depends on your application. One thing to keep in mind is that these buttons should not know what's in e.g. your login widget. They should be enabled when appropriate. Otherwise you are going to have a pretty hard to maintain widget there if you add more "pages".

You could also simplify this a little: void MainWindow::menuToggled() { auto widget = (container->currentWidget() == menuWidget) ? mdiContainer : menuWidget; container->setCurrentwidget(widget); }