How to add and access informations from dynamically created objects QT

frnklu20

"so if you would call this code more than once, it would still get "barramento1" as key
and override any barramento1 already put there. Might not be an issue but i did wonder."

That's the point! the user change the informations of the barramento
that he wants

"so it becomes part of the parent/owner system ?"
yes, it becomes part of Diagrama class

My point here is when i click on the screen add a label that represents a barramento object created at the same time.We're ok with that now

The next step is to add and change informations about it.You already saw the variables in class barramento,so here is what i thought:

When i create the label on the screen, i execute a Dialog from the class BarramDialog

0_1556887384690_f9d3a643-ddbc-41a8-97de-4edc7bf8e63a-image.png

And to get those values, i did:

if(modo=="barramento")
    {
        if(event->button()==Qt::RightButton)
        {
           int i=0;
            i+=1;
            CustomLabel *child = new CustomLabel(this);
            BarramDialog *barram=new BarramDialog;
            barram->setModal(true);

            child->setPixmap(QPixmap(url_barram));
            child->move(event->x(),event->y());
            connect(child, &CustomLabel::sendMousePosition, this, &Diagrama::showMousePosition);
            connect(child,&CustomLabel::opendialog, this, &Diagrama::justopendialog);
            child->show();
            barram->exec();##executing the dialog right after i create the label

            Barramento *barramento=new Barramento(this);
            barramento->setnum(barram->num);
            barramento->setang(barram->ang);
            barramento->settensao(barram->tensao);##getting those input values on the BarramDialog
            barramento->setnome(barram->nome);
            BarramentoMap["barramento"+QString::number(i)]=barramento;
            child->setProperty("datakey","barramento"+QString::number(i));
        }
    }

barramento.h

class Barramento
{

public:
    explicit Barramento(QWidget* parent =0 );
    Barramento();
    QString nome="padrão";
    int num;
    float tensao;
    float ang;

    void setnome(QString &);
    void setnum(int &);
    void settensao(float &);#these functions are responsible to change the variable values that i want 
    void setang(float &);

};

"Else, we are currently leaking the Barramento in the list as nothing will delete them on close down."
So how can i delete them?
" im just old school and like it to be certain." i get it hahaha

mrjj

@frnklu20 said in How to add and access informations from dynamically created objects QT:

ok. super its works as you want, no reason for alarm about the id.

So how can i delete them?

Well if you don't use the parent parameter in
explicit Barramento(QWidget* parent =0 );

then you can simply loop the and and call delete on each.
disclaimer*: fast typed. might have errors.

for (auto const& x : BarramentoMap)
{
delete x.second;
}

a good place to do it , would be the destructor of the main window. or where the BarramentoMap lives.

frnklu20

Ok! i'll do it

Just one more question, how can i do to support this link between the label and the class barramento with drag and drop functions?

diagrama.cpp

void Diagrama::dragEnterEvent(QDragEnterEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept();
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}

void Diagrama::dragMoveEvent(QDragMoveEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept();
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}

void Diagrama::dropEvent(QDropEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
        QByteArray itemData = event->mimeData()->data("application/x-dnditemdata");
        QDataStream dataStream(&itemData, QIODevice::ReadOnly);

        QPixmap pixmap;
        QPoint offset;
        dataStream >> pixmap >> offset;

        CustomLabel *newIcon = new CustomLabel(this);
        newIcon->setPixmap(pixmap);
        newIcon->move(event->pos() - offset);
        newIcon->show();
        newIcon->setAttribute(Qt::WA_DeleteOnClose);
        connect(newIcon, &CustomLabel::sendMousePosition, this, &Diagrama::showMousePosition);
        connect(newIcon,&CustomLabel::opendialog, this, &Diagrama::justopendialog);
        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept();
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}

these are the functions responsible for that, and the problem is on
void Diagrama::dropEvent(QDropEvent *event)

in this function i create another label with the same pixmap that i'm moving and i delete(just guessing) the old one, so the new one has no barramento object linked to it

what i thought was to get the property("datakey") of the old label (which is emitted by CustomLabel class) and do something like this:

new_label->setProperty("datakey",property("datakey"))
with this new line, the new_label overrides the informations of the old one, wich is not a problem beacuse it doesn't exist anymore.

But how can i do it? since that i don't have the emitted signal of custom label in drag and drop?

mrjj

Hi
Since you already pack some data
(the dataStream >> pixmap >> offset; )
could you not just include a QString with its datakey ID
with the pixmap and offset and set it on the newly created label?

frnklu20

ok, but how?

let's say I do this:
QString data;

dataStream>>pixmap>>offset>>data;

how the program will know that data=this->property("datakey")?

mrjj

@frnklu20
hi
you will put it in your self in startDrag or where you stuff the pixmap and point when drags starts.

frnklu20

oohhh yeahh
i got it!!!
Thank you man <<<<<<33333333

frnklu20

Hi,

I have a problem with the same question.Can you help me please?

mrjj

@frnklu20
Hi
if it's not super related to this thread,
then please make a new one.

frnklu20

It is!

is about how to add and access informations from dynamically created objects!

But now instead of using QLabels to portray my image, i'm using QGraphicsPixmapItems.

To update my program I started to use QGraphicItems, and like before I want to create a link between a specific graphic item that i added on the screen and a non-graphical object named Barramento.

diagramitem.cpp

DiagramItem::DiagramItem(DiagramType diagramType, QMenu *contextMenu,
             QGraphicsItem *parent)
    : QGraphicsPixmapItem(parent)
{
    QPainter *painter=new QPainter;
    myDiagramType = diagramType;
    myContextMenu = contextMenu;

    QPainterPath path;
    switch (myDiagramType) {
        case StartEnd:{
            QPixmap pixmap(url_trafo);
            myPolygon = pixmap;
            break;
    }
    case Gerador:{
            QPixmap pixmap2(url_gerador);
            myPolygon=pixmap2;
            break;
    }
    case Carga:{
            QPixmap pixmap3("C:/Users/Lukas/Desktop/simulight/images/carga");
            myPolygon=pixmap3;
            break;
    }
    default:{
            QPixmap pixmap4(url_barramento);
            myPolygon=pixmap4;
            break;
    }
    }
    setPixmap(myPolygon);
    setFlag(QGraphicsItem::ItemIsMovable, true);
    setFlag(QGraphicsItem::ItemIsSelectable, true);
    setFlag(QGraphicsItem::ItemSendsGeometryChanges, true);
}

that's the class responsible for the items

diagramscene.cpp
it handles the actions of adding objects on the screen dynamically

void DiagramScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if (mouseEvent->button() != Qt::LeftButton)
        return;

    DiagramItem *item;
    switch (myMode) {
        case InsertItem:
            
            item = new DiagramItem(myItemType, myItemMenu);

            addItem(item);
            item->setPos(mouseEvent->scenePos());
            emit itemInserted(item);
            if(myItemType==0)
            {
                int i=0;
                i+=1;
                Barramento *barramento=new Barramento();
                
                BarramentoMap["barramento"+QString::number(i)]=barramento;//error1
                item->setProperty("datakey","barramento"+QString::number(i)); //error2
            }
            break;

error1: no viable overloaded '='
error2: no member named 'setProperty' in 'DiagramItem'

And i'm asking myself if it is the same thing that we did beore, how can i fix it?Is there something that i have to do different whit QGraphicItems?

mrjj

Hi
DiagramItem do not have setProperty, so just add a new member variable to hold the "key"
QString datakey;
so you can just do
item->datakey="barramento"+QString::number(i);
It would be prittier if you defined an set function
item->SetDataKey( "barramento"+QString::number(i) );

For error 2, i guess you have the wrong declaration of the map.
I can't see it.

frnklu20

Hi,

Let me explain what i did,

I have add and access the information, so i created a custom QGraphicsPixmapItem that emits a signal when the item is clicked.

customgraphicsitem.h

class CustomGraphicsItem: public QGraphicsPixmapItem
{
public:
    CustomGraphicsItem(QGraphicsItem *parent=0);

     QString datakey;
     void SetDataKey(QString new_datakey);
      //i defined here the datakey variable and the function
signals:
    void sendInfo(const QVariant datakey);

protected:
    void mousePressEvent(QMouseEvent *event);
};

customgraphicsitem.cpp

CustomGraphicsItem::CustomGraphicsItem(QGraphicsItem *parent)
{

}

void CustomGraphicsItem::mousePressEvent(QMouseEvent *event)
{
    QPoint mouse_pos=event->pos();


    if(event->button()==Qt::RightButton){
        

    if(mouse_pos.x()<=this->boundingRect().size().width() && mouse_pos.y()<=this->boundingRect().size().height()){
//i don't know if it is the best way, if you have a better ideia talk to me

    if(mouse_pos.x()>0 && mouse_pos.y()>0){
          emit sendInfo(this->datakey);
       }
    }
    }
    else {
        event->ignore();
    }
}
void CustomGraphicsItem::SetDataKey(QString new_datakey)
{
    datakey=new_datakey;
}

Now in diagramscene i have a public slot named receiveinfo

diagramscene.cpp

void DiagramScene::receiveinfo(const QVariant &datakey)
{
    QMessageBox msgBox;
    msgBox.setText((datakey).toString());
    msgBox.exec();
}
//for now i just want to show the datakey in a messagebox when i click the item
void DiagramScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{if (mouseEvent->button() != Qt::LeftButton)
        return;

    DiagramItem *item;
    switch (myMode) {
        case InsertItem:
            
            item = new DiagramItem(myItemType, myItemMenu);

            addItem(item);
            item->setPos(mouseEvent->scenePos());
            emit itemInserted(item);
            if(myItemType==0)
            {
                int i=0;
                i+=1;
                Barramento *barramento=new Barramento();
                BarramentoMap["barramento"+QString::number(i)]=barramento;
                item->SetDataKey("barramento"+QString::number(i));
                connect(item, &CustomGraphicsItem::sendInfo, this, &DiagramScene::receiveinfo);
                //here i connect the item to the signal and the slots
            }

What i did wrong? qt guves me 3 errors that i don't know what they mean

error1:
'staticMetaObject' is not a member of 'QtPivate::FunctionPrivate<void....

error2:
"qt_metacall" is not a member of 'CustomGraphicItem'

error3:
static assertion failed: No Q_OBJECT in the class with the signal

What i did wrong?There is a better way to know if the QGraphicsItem was clicked?

SGaist

Hi,

Not all Qt classes by far inherit QObject. If you want signals and slots in your custom QGraphicsPixmapItem, then you also have to inherit QObject first.

The errors are mostly related to that.

Error 3 is pretty self-explanatory: you are missing the Q_OBJECT macro in your class declaration.

You are likely looking for QGraphicsItem::mouseReleaseEvent.

frnklu20

Ok!

I fixed the error3

class CustomGraphicsItem: public QGraphicsPixmapItem
{
    Q_OBJECT

public:

And now my mousePressEvent is defined in this way

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);

So it's fine i guess

but how can i inherit QObject in my custom QGraphicsPixmapItem?Because after i fixed those errors it only appears 1 error:
no matching function for call to 'QObject::connectImpl ....
that i think it must be from the signal that i'm emitting, so how can i fix this by inheriting qobject?

mrjj

Hi

how can i fix this by inheriting qobject?

class CustomGraphicsItem: public QObject, public QGraphicsPixmapItem {
...

and in cpp, also call it

CustomGraphicsItem (QGraphicsItem *parent = 0): QObject(), QGraphicsPixmapItem(parent)
{

}

frnklu20

I did it:

.h

class CustomGraphicsItem: public QObject, public QGraphicsPixmapItem
{
    Q_OBJECT

public:
    CustomGraphicsItem(QGraphicsItem *parent=0);

.cpp

CustomGraphicsItem::CustomGraphicsItem(QGraphicsItem *parent):
    QObject(), QGraphicsPixmapItem(parent)
{

But now it gives to me a lot of errors
unidefined reference to 'vtable for CustomGraphicsItem
undefined reference to 'CustomGraphicsItem::sendInfo(QVariant)
undefined reference to 'CustomGraphicsItem::metaObject() const
undefined reference to 'CustomGraphicsItem::qt_metacast(char const*)
undefined reference to 'CustomGraphicsItem::qt_metacall(QMetaObject::Call,int,void**)

why is that happening?

mrjj

Hi
Do you actually have those in cpp?
The body of the functions, i mean.

Also, if yes, you do have them still, then try delete build folder
and run rebuild all. (from the menu)

frnklu20

Hi,

Sorry for the delay to answer, i was in the period of exams in college.

After delete the build folder and rebuild all the program executed :)
But i don't know why my mousePressEvent of CustomGraphicItem is not working(not emitting any signal) and my drag and drop is not working either like it's causing inteference.

what is happening?

in customgraphicsitem.h the function is defined as:

protected:
     void mousePressEvent(QGraphicsSceneMouseEvent *event) override;

in customgraphicsitem.cpp :

void CustomGraphicsItem::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    QPointF mouse_pos=event->scenePos();

        if(event->button()==Qt::RightButton){


        if(mouse_pos.x()<=this->boundingRect().size().width() && mouse_pos.y()<=this->boundingRect().size().height()){


        if(mouse_pos.x()>0 && mouse_pos.y()>0){
              emit sendInfo(this->datakey);
           }
        }
        }
        else {
            event->ignore();
        }
}

what is the problem with it?

jsulm

@frnklu20 You have several conditions before emitting the signal: did you try to debug to see what happens? I guess one of your "if"s does not match.

J.Hilk

@frnklu20
the boundingRect rectangle is most likely not mapped to the scenePos. You should check that