Drag and Drop Crush when second time drag

Hi forum again me pls help me.

i just want to do that;

ive got two label and i want to drag first label text to drop second label and code worked fine(i dont know why :))). but i want to do this in second time it crushed.
i think i should to clear mimedata but how?? or what i should to do?

here is my . h file

Code:

---

public:
    explicit Dialog(QWidget *parent = nullptr);
    ~Dialog();
    void mousePressEvent(QMouseEvent *event) ;
    QDrag *drag = new QDrag(this);
    QMimeData *mimeData = new QMimeData;
    QString labeltext;
 
 
private:
    Ui::Dialog *ui;
 
protected:
    bool eventFilter(QObject *obj, QEvent *event);

---

and dialog .cpp

Code:

---

#include <QEvent>
#include <QDragEnterEvent>
#include <QDragMoveEvent>
#include <QDropEvent>
#include <QDebug>
#include <QMouseEvent>
#include <QDrag>
#include <QMimeData>
 
Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);
    ui->label_2->installEventFilter(this);
    ui->label_2->setAcceptDrops(true);
}
 
Dialog::~Dialog()
{
    delete ui;
}
 
void Dialog::mousePressEvent(QMouseEvent *event)
 {
     if (event->button() == Qt::LeftButton
         && ui->label->geometry().contains(event->pos()))
     {
 
           labeltext = ui->label->text();
 
         mimeData->setText(labeltext);
         drag->setMimeData(mimeData);
         drag->start();
     }
 }
 
bool Dialog::eventFilter(QObject *obj, QEvent *event)
{
    if (event->type() == QEvent::DragEnter)
    {
        QDragEnterEvent *tDragEnterEvent = static_cast<QDragEnterEvent *>(event);
        tDragEnterEvent->acceptProposedAction();
 
        return true;
    }
 
    else if (event->type() == QEvent::DragMove)
    {
        QDragMoveEvent *tDragMoveEvent = static_cast<QDragMoveEvent *>(event);
        tDragMoveEvent->acceptProposedAction();
 
        return true;
    }
 
 
    else if (event->type() == QEvent::Drop)
    {
        QDropEvent *tDropEvent = static_cast<QDropEvent *>(event);
        tDropEvent->acceptProposedAction();
 
        ui->label_2->setText(mimeData->text());
 
 
        return true;
    }
 
    return QObject::eventFilter(obj, event);
}

---

please help mee pleeeeaseeeee :((

(and pls i dont want to use subclass for this)

A crash is usually a good source to find what is wrong, e.g. by running the program in debugger and checking which call causes the crash.
Especially if you have a reliable way of triggering the crash.

Educated guess: the second time calls methods on a now invalid QDrag pointer.

Cheers,
_

All my respect sir,

What am i doing please show me the way

1) Compile the program in debug mode
2) Run the program in the debugger
3) Check where it crashes

Debugging a crash is the most fundamental thing to learn.

Telling you the cause and/or solution for this specific crash does not help you in the long run

Cheers,
_

Quote:

---

Educated guess: the second time calls methods on a now invalid QDrag pointer.

---

And probably an invalid QMimeData pointer as well, since QDrag::setMimeData() takes ownership and if the QDrag instance is destroyed, so will be the QMimeData instance.

Quote:

---

drag->start();

---

I can't find a QDrag:: start() method, so where did this come from, and how did you get the code to compile in the first place?

Quote:

---

Originally Posted by d_stranz

And probably an invalid QMimeData pointer as well, since QDrag::setMimeData() takes ownership and if the QDrag instance is destroyed, so will be the QMimeData instance.

---

Yep

Quote:

---

Originally Posted by d_stranz

I can't find a QDrag:: start() method, so where did this come from, and how did you get the code to compile in the first place?

---

Deprecated and thus not part of the API documentation.
But still in the header.

Cheers,
_