scala : double "selection changed" event raised for ListView component - scala

Question

here is the part of code:
val lsv_syns = new ListView[String]()
val scp_syns = new ScrollPane() {
listenTo(lsv_syns.mouse.moves,lsv_syns.selection)
reactions += {
case me: MouseExited => {
txf_mot.requestFocus()
}
case SelectionChanged(`lsv_syns`)=> {
println("sélection:"+lsv_syns.selection.items(0))
}
}
}
As you can see, the listView is in a scrollPane; don't pay attention to the mouseExited event, the interesting thing is the selectionChanged, which seems to be called twice when I only click on time on an other line, because the println is called two times.
thanks.

Answer 1

Well i also recently worked with a ListView and now that you mentioned it, it also does my calculation twice.
The answer seems to be related to mouse events. Following the stack trace SelectionChanged is called twice. One coming from the Java event MousePressed and one from MouseReleased.
When you change the selection with KeyEvents it is only called once.
My first (and I guess not nice) idea to avoid the problem would be to ignore one of the events:
reactions += {
case SelectionChanged(`lsv_syns`) if !lsv_syns.selection.adjusting => {
println("sélection:"+lsv_syns.selection.items(0))
}
}
Both ListSelection events share the same data except getValueIsAdjusting. So if you check for it you can avoid doing your stuff twice.
Warning: !lsv_syns.selection.adjusting will result in printing on key release and not on press!
If you put lsv_syns.selection.adjusting it will correspond to key press but it will also filter key events. As I said. Not nice at all...