How to temporarily remove items from a ChoiceBox (or maybe a ComboBox)? - combobox

Question

I've come across a somewhat perplexing conundrum. I've recently started to figure out how to work with listeners, thanks to some people on here, and I'm trying to find a way to use them in conjunction with choice/comboboxes to do something tricky. What I want to have happen is, when the user makes a selection from one of six linked boxes containing six choices, it removes that option from the other 5 boxes until either A: the option is changed to one of the remaining ones, or B: the option is changed to a null or default setting (to prevent getting "locked in" after picking, or maybe I can just make a reset button for that purpose). I've got a ChangeListener on each choicebox now, but various things I've tried (switch statements, assigning each answer a boolean, various attempts to use .getItems().remove() in vain, I've been at this a while) Has anyone figured or seen an example of how this could be done? Thanks in advance for any advice, you guys(and gals) have helped me learn by leaps and bounds these past few weeks.

Answer 1

if you want something like this:
I had this code in my program. it is nor really efficient, but was fine for me on a small set of data.
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.control.ChoiceBox;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
public class ConnectedComboBox<T> implements ChangeListener<T> {
private ObservableList<T> items;
private List<ChoiceBox<T>> comboBoxList = new ArrayList<>();
public ConnectedComboBox(ObservableList<T> items){
this.items = items;
if (this.items == null) this.items = FXCollections.observableArrayList();
}
public void addComboBox(ChoiceBox<T> comboBox){
comboBoxList.add(comboBox);
comboBox.valueProperty().addListener(this);
updateSelection();
}
public void removeComboBox(ChoiceBox<T> comboBox){
comboBoxList.remove(comboBox);
comboBox.valueProperty().removeListener(this);
updateSelection();
}
// this boolean needed because we can set combobox Value in updateSelection()
// this will trigger a value listener and update selection one more time => stack overflow
// this behavior occurs only if we have more than one equal item in source ObservableList<T> items list.
private boolean updating = false;
private void updateSelection() {
if (updating) return;
updating = true;
List<T> availableChoices = items.stream().collect(Collectors.toList());
for (ChoiceBox<T> comboBox: comboBoxList){
if (comboBox.getValue()!= null) {
availableChoices.remove(comboBox.getValue());
}
}
for (ChoiceBox<T> comboBox: comboBoxList){
T selectedValue = comboBox.getValue();
ObservableList<T> items = comboBox.getItems();
items.setAll(availableChoices);
if (selectedValue != null) {
items.add(selectedValue);
comboBox.setValue(selectedValue);
}
}
updating = false;
}
#Override
public void changed(ObservableValue<? extends T> observable, T oldValue, T newValue) {
updateSelection();
}
}
And here is how you use it:
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.ChoiceBox;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
public class MainFX extends Application {
#Override
public void start(Stage primaryStage) throws Exception {
HBox root = new HBox();
root.setSpacing(10);
ObservableList<String> values = FXCollections.observableArrayList("One", "Two", "Three", "Four","Five");
ChoiceBox<String> combo1 = new ChoiceBox<>();
combo1.setPrefWidth(100);
ChoiceBox<String> combo2 = new ChoiceBox<>();
combo2.setPrefWidth(100);
ChoiceBox<String> combo3 = new ChoiceBox<>();
combo3.setPrefWidth(100);
root.getChildren().addAll(combo1,combo2,combo3);
ConnectedComboBox<String> connectedComboBox = new ConnectedComboBox<>(values);
connectedComboBox.addComboBox(combo1);
connectedComboBox.addComboBox(combo2);
connectedComboBox.addComboBox(combo3);
primaryStage.setScene(new Scene(root,600,600));
primaryStage.show();
}
public static void main(String[] args){
launch(args);
}
}