QHBoxLayout delete QPushButton

sonichy

Delete QPushButton in QHBoxLayout fail.

QHBoxLayout *hbox = new QHBoxLayout;

void windowAdded(WId wid){
    Dock *dock = new Dock;
    dock->wid = wid;
    QPushButton *pushButton = new QPushButton(icon, NULL);
    pushButton->setUserData(DOCK, dock);
    hbox->addWidget(pushButton);
}

void windowRemoved(WId wid){
    for (int i=0; i<hbox->count();i++) {
        QLayoutItem *LI = hbox->layout()->itemAt((i));
        QPushButton *pushButton = qobject_cast<QPushButton*>(LI->widget());
        Dock *dock = (Dock*)(pushButton->userData(DOCK));
        if (dock->wid == wid) {
            delete LI;
        }
    }
}

mrjj

Hi
The layout owns it so
you must use
https://doc.qt.io/qt-5/qlayout.html#takeAt

and delete that. ( will also delete its widget as far as i remembers )

SimonSchroeder

I have to disagree with mrjj. It is true that the layout owns the push button. However, IIRC the push button also knows its parent and will delete itself from it when deleted. So, at least in theory your code should work.

Nevertheless, I am not sure if you correctly use setUserData/userData. I have never encountered it and the reason for this is that it is not part of the public API. So, the best advice is: Don't use it! Quick googling gave me this: https://stackoverflow.com/questions/8260763/about-using-an-undocumented-class-in-qt Their advice is to use QObject::setProperty instead. You are more likely to get help in this forum if you use only documented features.

sonichy

@SimonSchroeder Strange solved by these:
A layout in a big layout. delete cause overlap.
Change to:
A QWidget with the layout in a big layout, delete work fine.

QList<QPushButton *> list_pushButton = widget_app->findChildren<QPushButton *>();    //QWidget
for (int i=0; i<list_pushButton.count(); i++) {
    Dock *dock = (Dock*)(list_pushButton.at(i)->userData(DOCK));
            if (dock->wid == wid) {
                hbox_app->removeWidget(list_pushButton.at(i));    // QHBoxLayout in QWidget
                list_pushButton.at(i)->deleteLater();
            }
}