Hi Tomas, When I do that, the property is never set to null. If I use it for triggering the loading (when it is set to a non-null value) it is set for a lot more rows than those actually visible. In my test with a model containing 200 items of which the first 4 were visible, it was set to non-null for the first 23 items.
Am Dienstag, 27. Januar 2015 schrieb Tomas Mikula : > Hi Robert, > > instead of listening to visibleProperty(), listen to sceneProperty() > and cancel loading when scene becomes null. > > Tomas > > On Tue, Jan 27, 2015 at 1:16 PM, Robert Krüger <krue...@lesspain.de > <javascript:;>> wrote: > > Hi, > > > > either I don't see the forest for the trees or something is missing in > the > > TableView API as I cannot seem to implement something that seems a common > > requirement and was rather easy (not pretty though) in Swing. > > > > Imagine an application like OSX finder in its list view, i.e. something > > that displays a possibly very long list of files and displays thumbnails > > for them generated on the fly. For many files (e.g. video files) > extracting > > these thumbnails is an expensive operation and has to be performed in the > > background. My application does a very similar thing and uses a > TableView. > > What I want is to begin extracting video thumbnails as soon as their > > corresponding table row has become visible. I have done that in Swing in > > the past without any problem (for more info, you can read > > https://community.oracle.com/message/12810930). > > > > With JavaFX I have tried the following: > > > > 1) Trigger loading the thumbnail in the table cell when it is updated and > > the corresponding thumbnail isn't already there > > > > Result: Triggering works more or less as desired but how do I stop the > > loading process if the cell becomes invisible? If the user quickly > scrolls > > through a large number of rows and puts tons of thumbnail loading jobs on > > the queue I have not found a way to dequeue them, so this is unusable. I > > added output to the calls to the update method of the TableCell to see > > which instances are used and how their data is reset but the pattern I > see > > is not suitable for deciding which cell is currently visible. > > > > 2) Register a change listener to the TableCell’s visible property to make > > that control the image loading. > > > > Result: I don’t seem to get any change events when I do that, so it does > > not work at all for my purpose. > > > > I see no public API in table view to explicitly compute the items visible > > in the current viewport either. What am I missing. It can't be an > oversight > > in the API design, as the thing, I am trying to achieve appears rather > > basic. > > > > Thanks in advance for any hints, > > > > Robert > -- Robert Krüger Managing Partner Lesspain GmbH & Co. KG www.lesspain-software.com
