JavaFX: bindContent of TreeView selectedItems - javafx

Question

I want to bind a content of TreeView selected items list and bumped into a strange behaviour of the selected items change value when removing elements. I wrote a some test application:
public class TreeViewSelectedItemsBindingTest extends Application {
public class Item extends TreeItem<Integer> {
public Item(Integer... value) {
Arrays.stream(value).forEach(v -> getChildren().add(new TreeItem<Integer>(v)));
}
}
#Override
public void start(Stage primaryStage) throws Exception {
TreeView<Integer> treeView = new TreeView<>();
treeView.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
treeView.setRoot(new Item(0, 1, 2, 3, 4, 5, 6, 7, 8, 9));
treeView.getRoot().setExpanded(true);
treeView.setShowRoot(false);
ListView<TreeItem<Integer>> listView = new ListView<>();
Bindings.bindContent(listView.getItems(), treeView.getSelectionModel().getSelectedItems());
treeView.getSelectionModel().getSelectedItems()
.addListener((ListChangeListener<? super TreeItem<Integer>>) change -> {
System.out.println("Change: " + change);
System.out.println("TreeView size: " + treeView.getSelectionModel().getSelectedItems().size());
System.out.println("ListView size: " + listView.getItems().size());
System.out.println("-------------------");
});
HBox box = new HBox();
box.getChildren().addAll(treeView, listView);
primaryStage.setScene(new Scene(box));
primaryStage.show();
}
static public void main(String[] args) {
launch(args);
}
}
This application bind TreeView selected items to ListView items. Select in the tree view all elements from 0 to 9 and then press SHIFT+element 5, for example, to change selection from 0 to 5 elements. You will got an exeption:
Exception in thread "JavaFX Application Thread" java.lang.IndexOutOfBoundsException: toIndex = 9
It is because ListChangeListener.Change reports from index relative to initial unmodified list, not relative a list changed previously:
-------------------
Change: { [TreeItem [ value: 6 ]] removed at 6, }
TreeView size: 9
ListView size: 9
-------------------
Change: { [TreeItem [ value: 7 ]] removed at 7, }
TreeView size: 8
ListView size: 8
-------------------
You can see "removed at 6" then "removed at 7", but size of underlying lists also changed so index should not be increased here, i.e. all "removed at" should be at 6. And because of this a Bindings.bindContent is failed.

Answer 1

It is a bug JDK-8180359. As a workaround the bonded list should be updated as whole:
treeView.getSelectionModel().getSelectedItems().addListener(
(ListChangeListener<? super TreeItem<Model>>) change -> {
while (change.next()) {
listView.setAll(change.getList().stream()
.filter(Objects::nonNull)
.map(i -> i.getValue())
.collect(toList()));
}
});