[Qt-interest] Drag-n-Drop only works the first time

[Michael Jackson]

Just replying to my own thread. Drag-n-Drop onto a QGraphicsView only works
the first time because after that the QGraphicsScene is now valid and the
GraphicsScene is now fed the Drop event. I'll probably have to subclass the
graphics scene instead to implement the drop functionality.

Thanks, sorry for the noise.
Mike Jackson


On 4/5/10 3:10 PM, in article C7DFADE9.5AA3%mike.jackson at bluequartz.net,
"Michael Jackson" wrote:

> I have created a subclass of QGraphicsView in order to allow the user to
> drop a file onto the QGraphicsView widget and have the widget display the
> contents of the image file. The image loading code is in another class so I
> just figured I would hook everything up with Signals/Slots. The problem is
> taht the first drop works just fine. Subsequent drags from the file system
> onto the QGraphicsView widget fail to even show the "drag-n-drop" icon and
> in fact does not seem to accept the drop. If I omit the "emit
> loadImageFileRequested()" line of code then I can perform multiple drops
> onto the QGraphicsView widget without problems, of course now that I
> commented out the loading code nothing actually loads.)
>  My immediate question would be are there issues with emitting a signal from
> the DropEvent(....) method that I have implemented?
> 
> Here is the header:
> class QFSDroppableGraphicsView : public QGraphicsView  {
>     Q_OBJECT
>   public:
>     QFSDroppableGraphicsView(QWidget *parent = NULL);
>     void dragEnterEvent(QDragEnterEvent *event);
>     void dropEvent(QDropEvent *event);
>   signals:
>    void loadImageFileRequested(const QString &filename);
> };
> 
> Here is the implementation:
> void QFSDroppableGraphicsView::dropEvent(QDropEvent *event)
> {
>   QList<QUrl> urlList;
>   QString fName;
>   QFileInfo info;
> 
>   if (event->mimeData()->hasUrls())
>   {
>     urlList = event->mimeData()->urls(); // returns list of QUrls
>     // if just text was dropped, urlList is empty (size == 0)
> 
>     if ( urlList.size() > 0) // if at least one QUrl is present in list
>     {
>       fName = urlList[0].toLocalFile(); // convert first QUrl to local path
>       info.setFile( fName ); // information about file
>       QString ext = info.suffix();
>       if (ext.compare("tif") == 0
>           || ext.compare("jpg") == 0
>           || ext.compare("png") == 0
>           || ext.compare("bmp") == 0)
>       {
>         emit loadImageFileRequested(fName);
>       }
>     }
>   }
> }
> 
> The signals and slots are getting hooked up correctly as I can debug through
> the stack for the first drop.
> 
> Any help would be greatly appreciated.
> 
> --
> Mike Jackson
> Principal Software Engineer
> BlueQuartz Consulting
>