Reacting to mouse events on a TreeCell. Is it supposed to be this awkward?

[Scott Palmer]

Will do.

I also just noticed (after using Bindings.select(this.sceneProperty(),
"window", "showing") to try to trigger my "diconnecting") that in 7u40
TreeCells seem to remain connected to the scene until I force the tree to
repaint.
In my app every time I open a document I rebuild a tree.  even when
listening to the above mentioned binding, nothing was triggering as I
loaded new documents until I resized my UI.  Then suddenly all those unused
TreeCells were "let go".


Scott


On Tue, Oct 8, 2013 at 3:48 PM, Jonathan Giles <jonathan.giles at oracle.com>wrote:

> I note right at the end you say you're using 7u40. In the JavaFX 2.x
> series of releases it is true that TreeView misbehaved a bit around cell
> reuse. This should no longer be the case in JavaFX 8.0. In any case, the
> best option is to file a bug report and discuss it further in there,
> especially so if you can reproduce the issue in JavaFX 8.0.
>
> One thing that sticks out: you don't say if you're using
> WeakEventHandler or EventHandler instances. If you're using EventHandler
> you could consider using WeakEventHandler. This may help to alleviate
> some of the memory leak.
>
> -- Jonathan
>
> On 9/10/2013 8:37 a.m., Scott Palmer wrote:
> > I'm investigating a memory leak and it seems that the culprit is event
> > listeners attached to TreeCells
> >
> > The GC roots of my leaks are deep in the JavaFX window/event system
> >
> > In a class extending TreeCell,  am calling methods on such as:
> >
> > setOnContextMenuRequested(contextMenuRequestHandler);
> > setOnMouseClicked(mouseEventHandler);
> > setOnDragDetected(dragDetectedHandler);
> >
> > All of the event handlers in this case will have a reference to the
> > TreeCell, either via the implicit reference of the anonymous inner class,
> > or an explicit member
> >
> > I do this in updateItem when the cell is not empty and has a non-null
> item.
> > If updateItem is called and the cell is empty or has a null item then I
> > clear the event handlers with:
> >
> > setOnContextMenuRequested(null);
> > setOnMouseClicked(null);
> > setOnDragDetected(null);
> >
> > The problem is that TreeView doesn't seem to reuse TreeCells very much.
>  It
> > mostly creates new ones.  This means that many TreeCells are disconnected
> > from the scene graph and "lost" while there is still an event handler
> > connected to it.
> >
> > Am I doing something wrong?
> > This seemed like the correct way to deal with dragging and double
> clicking
> > on tree nodes.
> >
> > The tutorial here:
> > http://docs.oracle.com/javafx/2/ui_controls/tree-view.htm#BABDEADA
> >
> > only goes so far as to add a context menu. (My context menu needs to be
> > constructed dynamically.)  So I'm not sure if I'm "allowed" to connect
> > event handlers to TreeCells in this way, but I don't know what the
> > alternative is.
> >
> > I suppose I would have to listen to something to ensure the TreeCell is
> > still part of the scene graph and disconnect the listeners when that
> > changes.  It seems a bit awkward.
> >
> >
> > Scott
> > (I'm using 7u40)
>
>