Qt - Calling widget parent's slots
- by bullettime
I wrote a small program to test accessing a widget parent's slot. Basically, it has two classes:
Widget:
namespace Ui
{
class Widget;
}
class Widget : public QWidget
{
Q_OBJECT
public:
Widget(QWidget *parent = 0);
~Widget();
QLabel *newlabel;
QString foo;
public slots:
void changeLabel();
private:
Ui::Widget *ui;
};
Widget::Widget(QWidget *parent)
: QWidget(parent), ui(new Ui::Widget)
{
ui->setupUi(this);
customWidget *cwidget = new customWidget();
newlabel = new QLabel("text");
foo = "hello world";
this->ui->formLayout->addWidget(newlabel);
this->ui->formLayout->addWidget(cwidget);
connect(this->ui->pushButton,SIGNAL(clicked()),cwidget,SLOT(callParentSlot()));
connect(this->ui->pb,SIGNAL(clicked()),this,SLOT(changeLabel()));
}
void Widget::changeLabel(){
newlabel->setText(this->foo);
}
and customWidget:
class customWidget : public QWidget
{
Q_OBJECT
public:
customWidget();
QPushButton *customPB;
public slots:
void callParentSlot();
};
customWidget::customWidget()
{
customPB = new QPushButton("customPB");
QHBoxLayout *hboxl = new QHBoxLayout();
hboxl->addWidget(customPB);
this->setLayout(hboxl);
connect(this->customPB,SIGNAL(clicked()),this,SLOT(callParentSlot()));
}
void customWidget::callParentSlot(){
((Widget*)this->parentWidget())->changeLabel();
}
in the main function, I simply created an instance of Widget, and called show() on it. This Widget instance has a label, a QString, an instance of customWidget class, and two buttons (inside the ui class, pushButton and pb). One of the buttons calls a slot in its own class called changeLabel(), that, as the name suggests, changes the label to whatever is set in the QString contained in it. I made that just to check that changeLabel() worked. This button is working fine. The other button calls a slot in the customWidget instance, named callParentSlot(), that in turn tries to call the changeLabel() slot in its parent. Since in this case I know that its parent is in fact an instance of Widget, I cast the return value of parentWidget() to Widget*. This button crashes the program. I made a button within customWidget to try to call customWidget's parent slot as well, but it also crashes the program. I followed what was on this question. What am I missing?
