[solved]Dynamically removing QPushButtons from Flowlayout

[neff]

Hi all,

I read a few tutorials and started to experiment with qt but I ran into a problem I just don't understand.
So, I'm trying to add and remove QPushButtons to/from a flowlayout (the one from the examples here) which works quite well except for the last item.
Here is my code:

MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)
{
 
 
    deletebutton = new QPushButton("delete",this);
    addbutton = new QPushButton("add",this);
 
    hbox = new QHBoxLayout();
    hbox->addWidget(deletebutton);
    hbox->addWidget(addbutton);
 
    QWidget* widget = new QWidget(this);
    flowlayout = new FlowLayout(widget);
    widget->setLayout(flowlayout);
    QScrollArea *scrollArea = new QScrollArea();
    scrollArea->setWidgetResizable(true);
    scrollArea->setWidget(widget);
 
    vbox = new QVBoxLayout(this);
    vbox->addLayout(hbox);
    vbox->addWidget(scrollArea);
 
    setLayout(vbox);
 
    connect(deletebutton, SIGNAL(clicked()), this, SLOT(deleteButton()));
    connect(addbutton, SIGNAL(clicked()), this, SLOT(addButton()));
 
}
 
void MyWidget::deleteButton() {
 
 
    flowlayout->takeAt(0);
    flowlayout->update();
 
    qDebug() <<"deleted: "<<flowlayout->count();
}
 
void MyWidget::addButton() {
 
    QPushButton* newButton = new QPushButton("button");
    flowlayout->addWidget(newButton);
    flowlayout->update();
    connect(newButton, SIGNAL(clicked()), this, SLOT(buttonpressed()));
 
    qDebug() <<"added: "<<flowlayout->count();
}
 
void MyWidget::buttonpressed() {
 
 
   qDebug() <<"button pressed";
 
}

MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)
{


    deletebutton = new QPushButton("delete",this);
    addbutton = new QPushButton("add",this);

    hbox = new QHBoxLayout();
    hbox->addWidget(deletebutton);
    hbox->addWidget(addbutton);

    QWidget* widget = new QWidget(this);
    flowlayout = new FlowLayout(widget);
    widget->setLayout(flowlayout);
    QScrollArea *scrollArea = new QScrollArea();
    scrollArea->setWidgetResizable(true);
    scrollArea->setWidget(widget);

    vbox = new QVBoxLayout(this);
    vbox->addLayout(hbox);
    vbox->addWidget(scrollArea);

    setLayout(vbox);

    connect(deletebutton, SIGNAL(clicked()), this, SLOT(deleteButton()));
    connect(addbutton, SIGNAL(clicked()), this, SLOT(addButton()));

}

void MyWidget::deleteButton() {


    flowlayout->takeAt(0);
    flowlayout->update();

    qDebug() <<"deleted: "<<flowlayout->count();
}

void MyWidget::addButton() {

    QPushButton* newButton = new QPushButton("button");
    flowlayout->addWidget(newButton);
    flowlayout->update();
    connect(newButton, SIGNAL(clicked()), this, SLOT(buttonpressed()));

    qDebug() <<"added: "<<flowlayout->count();
}

void MyWidget::buttonpressed() {


   qDebug() <<"button pressed";

}

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When I want to delete the last button, I get the correct qDebug() output (0), but the QPushButton does not disappear and when I click on it, it still produces the "button pressed" output. Everything else works just fine. I can add buttons and every button disappears when I click on delete.

What am I doing wrong?

Thanks!

[Lesiok]

How about this :

void MyWidget::deleteButton()
{
    QLayoutItem *item = flowlayout->takeAt(0);
    if( item )
    {
        delete item;
    }
 
    qDebug() <<"deleted: "<<flowlayout->count();
}

void MyWidget::deleteButton()
{
    QLayoutItem *item = flowlayout->takeAt(0);
    if( item )
    {
        delete item;
    }

    qDebug() <<"deleted: "<<flowlayout->count();
}

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[neff]

Thank you for your reply.
Unfortunately the proposed correction doesn't solve the problem.
If I omit "flowlayout->update()" nothing in my program changes after I press the delete button (all Buttons remain in the flowlayout and all buttons still work). If I add "flowlayout->update()" to your correction, the program behaviour is the same as explained in the top post.

I tried a bit more and now I have the behaviour I aimed for with:

void MyWidget::deleteButton() {
 
    QLayoutItem *item = flowlayout->takeAt(0);
 
   if( item )
   {
      item->widget()->hide();
      delete item->widget();
      delete item;
    }
 
    qDebug() <<"deleted: "<<flowlayout->count();
}

void MyWidget::deleteButton() {

    QLayoutItem *item = flowlayout->takeAt(0);
   
   if( item )
   {
      item->widget()->hide();
      delete item->widget();
      delete item;
    }

    qDebug() <<"deleted: "<<flowlayout->count();
}

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delete item->widget(); makes the button disappear from the layout.
item->widget()->hide(); makes sure that the buttons that are left get rearranged.