QListWidget reorder with Drag and Drop

[szh1]

Is there a way to allow a user to reorder QListWidgetItems in a QListWidget by dragging and dropping them, like you can do in Windows Explorer?

[t3chNo]

Yes, set listWidget's dragDropMode to QAbstractItemView::DragDrop and defaultDropAction to Qt::MoveAction.

[szh1]

I tried this, but when I try to drag an item, it just selects more items.

[t3chNo]

Set selectionMode to QAbstractItemView::SingleSelection.

[szh1]

Then, when I try to drag it, it just selects a different row.

[goetz]

This does the job:

@
setDragDropMode(QAbstractItemView::InternalMove);
@

[t3chNo]

Set dragEnabled to true.

[szh1]

Neither of those are working! :(
Am I the only one with this problem?

[t3chNo]

Which platform are you working on? Is your qt compiled with QT_NO_DRAGANDDROP defined?

[szh1]

I am using Windows 7 with the Qt SDK downloaded from qt.nokia.com/downloads. I did not build it myself.

[goetz]

This works for me:

@
#include <QApplication>
#include <QListWidget>

int main(int argc, char **argv)
{
QApplication a(argc, argv);

QListWidget lw;
for(int i = 1; i < 10; ++i)
    lw.addItem(new QListWidgetItem(QString("Item %1").arg(i)));
lw.setDragDropMode(QAbstractItemView::InternalMove);

lw.show();

a.connect(&a, SIGNAL(lastWindowClosed()), &a, SLOT(quit()));
a.exec&#40;&#41;;

}
@

[szh1]

Strange. It works for me, too. I wonder why my other application doesn't then.

[goetz]

Do you use a user interface made with Qt Designer and did you change some of the drag/drop settings there?

[t3chNo]

Do you use QListWidget or QListWidget inherited widget? If you inherit from listWidget and use mouse or drag events and didn't pass event to QListWidget, drag and drop will not work.

[szh1]

I made it with Qt Designer and I changed the drag and drop properties a lot, but now I changed them back to just dragDropMode = internalMove and put the others back to default. The selection mode is ExtendedSelection, but I tried the default, too.

[goetz]

That should work. I tried this with designer and could move the items in the preview mode (Ctrl-R/Cmd-R). That should work in the real code too, if you do not change other drag/drop settings there too.

[szh1]

Even stranger news:

I created a new project, copied and pasted all of the code / widgets, and now its working!

Any ideas why this happened and how to prevent it in the future?

[goetz]

Sorry, I do not have any clue what's happening there. Maybe some alien code from outer space? :-)

[t3chNo]

Here is my scenario: You use visual studio. Your code had little error. Complier didn't compile code and ran old executable.

[szh1]

Actually, I use Qt Creator.