mvvmfx/src/main/java/de/saxsys/mvvmfx/utils/itemlist/SelectableItemList.java
private void createIndexEvents() {
		selectionModel
                .selectedIndexProperty()
				.addListener((bean, oldVal, newVal) -> {
                    int index = newVal.intValue();
                    ListType item = index == -1 ? null : modelListProperty()
                            .get(index);
                    selectedItem.set(item);
                });
		
		selectedItem.addListener((observable, oldVal, newVal) -> {

            // Item null
            if (newVal == null) {
                selectionModel.select(-1);
                selectedItem.set(null);

            } else {
                int index = modelListProperty().get().indexOf(newVal);
                // Item not found
                if (index != -1) {
                    selectionModel.select(index);
                } else {
                    // If item not found - Rollback
                    selectedItem.set(oldVal);
                }
            }

        });
	}
private void createIndexEvents() {
		selectionModel
                .selectedIndexProperty()
				.addListener((bean, oldVal, newVal) -> {
                    int index = newVal.intValue();
                    ListType item = index == -1 ? null : modelListProperty()
                            .get(index);
                    selectedItem.set(item);
                });
		
		selectedItem.addListener((observable, oldVal, newVal) -> {

            // Item null
            if (newVal == null) {
                selectionModel.select(-1);
                selectedItem.set(null);

            } else {
                int index = modelListProperty().get().indexOf(newVal);
                // Item not found
                if (index != -1) {
                    selectionModel.select(index);
                } else {
                    // If item not found - Rollback
                    selectedItem.set(oldVal);
                }
            }

        });
	}
When the selected item changed we want to set the index property too