TreeView scrolling jumps when using large graphic nodes (TornadoFX/JavaFX) - javafx

Question

In the following TornadoFX/Kotlin code
import javafx.scene.control.TreeItem
import javafx.scene.control.TreeView
import tornadofx.*
class MyObj {
var type : Int = 0
constructor(type : Int) {
this.type = type
}
}
class MainView: View("Minimal TV demo") {
var treeRoot : TreeItem<MyObj> = TreeItem()
var objectsTreeView : TreeView<MyObj>? = null
override val root = vbox {
objectsTreeView = treeview(treeRoot) {
showRootProperty().value = false
cellFormat {
if(it.type == 0) {
text = "Test"
graphic = null
}
else {
text = null
graphic = vbox {
label("Label 1")
button("123")
textarea {
prefWidth = 100.0
prefHeight = 125.0
}
}
}
}
}
}
init {
with (root) {
for(i in 1..10) {
val x = TreeItem(MyObj(0))
treeRoot.children.add(x)
x.children.add(TreeItem(MyObj(1)))
}
}
}
}
when opening a few of the tree items and scrolling the tree view, the tree view contents and slider seems to act rather "jumpy", i.e. when I move the slider down, the mouse moves but the slider and content stay where it is, until the mouse gets so far down, then the content jumps. It just doesn't feel or look good.
I believe I could get around this by adding separate TreeItem's for each UI element row, but is there a way to achieve a smooth scroll without doing this? I tried suing a fixed cell height, which seems to work, but of course this doesn't look right at all given that some rows a shorter than others.

Answer 1

Don't use cellFormat for complex tree UIs, since the elements will be recreated very rapidly and most probably cause flicker. Your best bet is to create a subclass of TreeCellFragment and configured it using the cellFragment call.
Now you can create the UI only once per Tree cell, and reuse it when the data it represents changes. This is much more performant.