QListView in a QTabWidget tab - External Drop Not Working

[steveq]

Hi all,

I have now solved this.

As my drop was not item dependent, that is I didn't care what was under the drop, so long as it was the list, I didn't need to subclass the QStandardItemModel. Instead I simply subclassed the QListView with the following overridden methods:

	void dragEnterEvent(QDragEnterEvent *e);
	void dropEvent(QDropEvent *ev);
	void dragMoveEvent(QDragMoveEvent* event);

I can now drop on my list and I will receive the filename of the file that was dropped. I then "emit" this filename to my parent to act on it accordingly.

Thanks for all your help.

Steve Q. :-)

[Luzz T]

hi @steveq ，

I have encountered the same difficulties as you. then I follow your way : setAceeptDrop(true) and overridden methods

	void dragEnterEvent(QDragEnterEvent *e);
	void dropEvent(QDropEvent *ev);
	void dragMoveEvent(QDragMoveEvent* event);

and add QDebug() in methods, but I don't see any output of console, and ListView still gives me the round circle with the line through it, indicating I can't drop. I'm obviously missing something here, but I just don't know what it is!

[jsulm]

@Luzz-T Please show the code of the class where overriding these methods and show how you're using this class.

[Luzz T]

@jsulm
I only want get file name by external drop. ListViewDrop class inherits QListView

ListViewDrop.h

#ifndef LISTVIEWDROP_H
#define LISTVIEWDROP_H

#include <QListView>

namespace Ui {
class ListViewDrop;
}

class ListViewDrop : public QListView
{
    Q_OBJECT
public:
    explicit ListViewDrop(QWidget *parent = nullptr);
    ~ListViewDrop();

protected:
    void dragEnterEvent(QDragEnterEvent* ev) override;
    void dragMoveEvent(QDragMoveEvent *e) override;
    void dropEvent(QDropEvent* ev) override;
};

#endif // LISTVIEWDROP_H

ListViewDrop.cpp

#include "listviewdrop.h"
#include <qdebug.h>
#include <QDragEnterEvent>
#include <QDropEvent>
#include <QMimeData>
#include <QUrl>

ListViewDrop::ListViewDrop(QWidget* parent):
    QListView(parent)
{
    this->setAcceptDrops(true);

}

ListViewDrop::~ListViewDrop()
{

}

void ListViewDrop::dragEnterEvent(QDragEnterEvent *ev)
{
    qDebug() << "ListViewDrop::dragEnterEvent";
    if(ev->mimeData()->hasUrls())
    {
        ev->accept();
    }
    //ev->ignore();
}

void ListViewDrop::dropEvent(QDropEvent *ev)
{
    qDebug() << "ListViewDrop::dropEvent";
    if(ev->mimeData()->hasUrls())
    {
        QList<QUrl> urls = ev->mimeData()->urls();

        for(int i=0; i<urls.size(); i++)
        {
            qDebug() << urls.at(i).toLocalFile();
        }
    }
}

void ListViewDrop::dragMoveEvent(QDragMoveEvent *e) {
    qDebug() << "ListViewDrop::dragMoveEvent";
}

I create a ListViewDrop is in a QWidget

Thanks heaps in advance.

[jsulm]

@Luzz-T said in QListView in a QTabWidget tab - External Drop Not Working:

I create a ListViewDrop is in a QWidget

Please show how

[JonB]

@Luzz-T
First you must answer @jsulm's question.

But I see two possible issues in your current code, which may (or may not) need addressing after you have sorted out why your drag methods are not being hit at all:

• Your dragMoveEvent(QDragMoveEvent *e) does not accept the event. You need to have that as well as dragEnterEvent() accept the drag, else you are liable to end up with the "no drop" indicator. dropEvent should also accept it, I don't know if that matters in your case.

• In your dragEnterEvent you use ev->accept();. I'm not sure whether it matters, but here (and the other two methods) you are supposed to use acceptProposedAction().

[Luzz T]

@jsulm

"create" actually I use qt Designer, Layout following :

In the picture above ，the red box is the “ListViewDrop” of my promotion by QListView，and "SelectView" used in main.cpp

#include "selectview.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    SelectView w;
    w.show();
    return a.exec();
}

[Luzz T]

@JonB

Thanks for the tip. This is a test code, which I will pay attention to in development

[JonB]

@Luzz-T
In addition to my earlier points, you may need to add the following:

listView->setDropIndicatorShown(true);

Also if your list view has a model look at what listView->model()->supportedDropActions() is returning. P.S. And also probably QAbstractItemModel::mimeTypes(), dropMimeData(), canDropMimeData() too --- in a word, are you using a model with your QListView?

I think you should implement your dragMoveEvent() now, as I found without that I got stick with a "no-entry" drop indicator all the time.

The important is to confirm whether any of your drag/drop overrides report a qDebug() output as their first line?

Finally, in Designer did you set any of the properties on your listView, there are several related to d&d?

[Luzz T]

@JonB
Thank you for your suggestions. I found the problem. The dragDropMode attribute is not set, it defaults to
NoDragDrop . But strangely, the default attribute does not work in Windows, and the default value NoDragDrop is OK in MacOS,
Also the version of QT may be different or for other reasons

For all that It's already working. Thank all