QObject::connect: Cannot connect (null)

saeedhardan

Hi,
i'm trying to implement a checkbox within itemdelegate .
This is my code :
BooleanWidget.h
@
class BooleanWidget : public QWidget
{
Q_OBJECT
QCheckBox * checkBox;

public:
BooleanWidget(QWidget *parent = 0):
QWidget(parent)
{
checkBox = new QCheckBox(this);
QHBoxLayout * layout = new QHBoxLayout(this);
layout->addWidget(checkBox,0, Qt::AlignCenter);
}

bool isChecked(){
    return checkBox->isChecked();
}
void setChecked(bool value){
    checkBox->setChecked(value);
}

signals:
void toggled(bool value);

private:
};
@

CheckBoxDelegate.h
@
class CheckBoxDelegate : public QItemDelegate
{
Q_OBJECT
private:
BooleanWidget *checkbox;

public:
CheckBoxDelegate();
CheckBoxDelegate(QObject *parent);
~CheckBoxDelegate();
void setEditorData( QWidget *editor,const QModelIndex &index )const;
void setModelData( QWidget *editor,QAbstractItemModel *model,const QModelIndex &index )const;
QWidget *createEditor( QWidget parent,const QStyleOptionViewItem &/ option /,const QModelIndex &/ index */ )const;
void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const;

public slots:
void changed( bool );

};
@

CheckBoxDelegate.cpp
@
QWidget *CheckBoxDelegate::createEditor( QWidget parent,const QStyleOptionViewItem &/ option /,const QModelIndex &/ index */ ) const
{
//BooleanWidget editor = new BooleanWidget( parent );
BooleanWidget * editor = qobject_cast<BooleanWidget>(parent);
connect( editor, SIGNAL(toggled(bool)), this, SLOT(changed(bool)));

return editor;

}
@

As you can see BooleanWidget does have the macro Q_OBJECT .
But the @ qobject_cast<BooleanWidget*>(parent);@

always returns null . why is that ?

SGaist

Hi,

parent is not a BooleanWidget. The purpose of createEditor is to create a new editor, so your commented line was fine.

saeedhardan

thanks it works , but now i added

@const QModelIndex &index@

to the signal and slot , but i get the error :

QObject::connect: No such signal BooleanWidget::toggled(bool,index)

my signal is :

@ void toggled(bool value,const QModelIndex &index);@

SGaist

From your original post in the BooleanWidget.h snippet, it's not

saeedhardan

This is the new one :

@class BooleanWidget : public QWidget
{
Q_OBJECT
QCheckBox * checkBox;

public:
BooleanWidget(QWidget *parent = 0):
QWidget(parent)
{
checkBox = new QCheckBox(this);
QHBoxLayout * layout = new QHBoxLayout(this);
layout->addWidget(checkBox,0, Qt::AlignCenter);
}

bool isChecked(){
    return checkBox->isChecked();
}
void setChecked(bool value){
    checkBox->setChecked(value);
}

signals:
void toggled(bool value,const QModelIndex &index);

private:
};@

@class CheckBoxDelegate : public QItemDelegate
{
Q_OBJECT
private:
BooleanWidget *checkbox;

public:
CheckBoxDelegate();
CheckBoxDelegate(QObject *parent);
~CheckBoxDelegate();
void setEditorData( QWidget *editor,const QModelIndex &index )const;
void setModelData( QWidget *editor,QAbstractItemModel *model,const QModelIndex &index )const;
QWidget *createEditor( QWidget parent,const QStyleOptionViewItem &/ option /,const QModelIndex &/ index */ )const;
void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const;

public slots:
void changed( bool ,const QModelIndex &index );

};
@

@
void CheckBoxDelegate::changed( bool value ,const QModelIndex &index )
{
BooleanWidget checkbox = qobject_cast<BooleanWidget>( sender() );
checkbox->setChecked(value);
emit commitData( checkbox );
emit closeEditor( checkbox );
QWidget t;
QMessageBox::information(&t,"yay","yay index: "+index.row());
}
QWidget *CheckBoxDelegate::createEditor( QWidget *parent,const QStyleOptionViewItem & option ,const QModelIndex & index ) const
{
BooleanWidget editor = new BooleanWidget( parent );
//BooleanWidget * editor = qobject_cast<BooleanWidget>(parent);
connect( editor, SIGNAL(toggled(bool,index)), this, SLOT(changed(bool,index)));

return editor;

}
@

saeedhardan

and another thing , why do i have to click like 3 times for the checkbox to get checked ?

SGaist

Your SIGNAL and SLOT macros are wrong, you gave the variable name not the type:

@connect( editor, SIGNAL(toggled(bool,QModelIndex)), this, SLOT(changed(bool,QModelIndex)));@

saeedhardan

Please ignore this : "but even though i get no error the slot CheckBoxDelegate::changed() doesn't get called because i dont get any messagebox ("yay") " .

The situation now is :

- That signal method works , thanks a lot .
- I still the first time the window opens i have to click the checkbox like 3 time for it to get checked (but only first time meaning after i checked it for the first time then i can check/uncheck with only one click)
- where is the best place to emit a signal (toggeled()) with index . i mean which function is responsible for changing the state of the checkbox ,(sorry im not that good with itemdelegate).