Javafx combobox not updating dropdown size upon change on realtime?

Question

I am using Javafx v8.0.25-b18.

The problem I occur is that the size of the dynamic combox's dropdown list doesn't change, so if I had initially two items in the dropdown, then the dropdown size will be good for two items, but if I now populate the dynamic combox with three items then I get a small scrollbar inside!?, If I remove an item - I will have a blank space in the combox !?

I want to "reset" the dropdown size each time I put values into it, so it will be the right size each time it gets populated at runtime.

To clarify even more I am adding three images:
1. The first screenshot shows the initial dropdown size of 2

2. The second screenshot shows the same combox, where now at runtime I am adding 2 values, I EXPECT it to have now a dropdown with the size of 4, but instead the dropdown size stays 2 and only adds an unwanted scrollbar

3. Last screenshot is when I remove items and only one item remains in the combox, I EXPECT to see a dropdown of 1 item, but instead I unfortunately see a dropdown the size of 2 thus an empty space instead of the second item

I am adding the simple code to create this scenario, I want to thank @Gikkman that helped getting this far and the code is actually his!

public class Test extends Application {

private int index = 0;

@Override
public void start(Stage primaryStage) throws IOException {

VBox vbox =  new VBox();
vbox.setSpacing(10);
vbox.setAlignment(Pos.CENTER);

final ComboBox<String> box = new ComboBox<>();
box.setPrefWidth(200);
box.setVisibleRowCount(10);

Button add = new Button("Add");
Button remove = new Button("Remove");

add.setOnAction(    new EventHandler<ActionEvent>() {
  @Override
  public void handle(ActionEvent event) {
    box.getItems().add("Item " + index++);
    box.getItems().add("Item " + index++);
  }
});


remove.setOnAction( new EventHandler<ActionEvent>() {
  @Override
  public void handle(ActionEvent event) {
    if( index > 0 )
      box.getItems().remove(--index);
  }
});


vbox.getChildren().addAll(add, remove, box);


Scene scene = new Scene(vbox);

primaryStage.setScene(scene);
primaryStage.show();
}

public static void main(String[] args) {
  launch(args);
}
}

Answer 1

Try this:

box.hide(); //before you set new visibleRowCount value
box.setVisibleRowCount(rows); // set new visibleRowCount value
box.show(); //after you set new visibleRowCount value

It's works for me with editable comboBox and I think it will work in your case.

Answer 2

I had same problem and I solved it with a quick trick. Just try to show and immediately hide !

add.setOnAction(new EventHandler<ActionEvent>() {
  @Override
  public void handle(ActionEvent event) {
    box.getItems().add("Item " + index++);
    box.getItems().add("Item " + index++);
    box.show();
    box.hide();
  }
});