Javafx Combox getSelectedIndex returns -1

Question

I'm new to JavaFX, I'm getting this weird exception whenever I select an item from ComboBox, I have a bunch of records in the database that I'm fetching and putting in the combo box as String, the thing is when I select the items in the Combobox I get ArrayIndexOutOfBoundsException: -1, sometimes I can display the information needed from the ComboBox and sometimes I can't, what is causing this error? and how can I fix it, help will be appreciated?

Here is the ComboBox action method:

@FXML
private ComboBox<String> recherche;

@FXML
private void Combo(ActionEvent event) {
        Platform.runLater(() -> {

            int selectedIndex = this.recherche.getSelectionModel().getSelectedIndex();
            System.out.println("**************selected intedx "+selectedIndex); //prints -1 and throws ArrayOutOfBoundsException

            ObservableList<String> listPayment = FXCollections
                    .observableArrayList(PaymentQueries.listOfPayamentDates(listOfData);
            recherche.setItems(listPayment);
            recherche.setEditable(true);
            //for autocompletion
            TextFields.bindAutoCompletion(recherche.getEditor(), recherche.getItems());

        });

    }

I call this method before I show the Combobox:

 public void reload() {
        Platform.runLater(() -> {

            clearFields();
            ObservableList<String> listEnfant = FXCollections.observableArrayList(EnfantQueries.getData().getNoms());
            recherche.setItems(listEnfant);
            recherche.setEditable(true);
            TextFields.bindAutoCompletion(recherche.getEditor(), recherche.getItems());
        });

    }

Answer 1

As this is a common symptom with many causes, it may help to examine it in isolation. Starting from the example seen here, the variation below listens to the combo's SelectionModel and displays the value of the current selection in a TextField. Note that the combo's selected index becomes -1 when the Clear button is used to clear the combo's model.

SingleSelectionModel selectionModel = comboBox.getSelectionModel();
TextField selection = new TextField(String.valueOf(selectionModel.getSelectedIndex()));
selectionModel.selectedIndexProperty().addListener((Observable o) -> {
    selection.setText(String.valueOf(selectionModel.getSelectedIndex()));
});
…
dialogPane.setContent(new VBox(8, textField, datePicker, comboBox, selection, …));

Complete example:

import java.time.LocalDate;
import java.util.Optional;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.Observable;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.ComboBox;
import javafx.scene.control.DatePicker;
import javafx.scene.control.Dialog;
import javafx.scene.control.DialogPane;
import javafx.scene.control.SingleSelectionModel;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

/**
 * @see https://stackoverflow.com/a/46504588/230513
 * @see http://stackoverflow.com/q/44147595/230513
 * @see http://www.javaworld.com/article/2991463/
 */
public class DialogTest extends Application {

    @Override
    public void start(Stage primaryStage) {
        Dialog<Results> dialog = new Dialog<>();
        dialog.setTitle("Dialog Test");
        dialog.setHeaderText("Please specify…");
        DialogPane dialogPane = dialog.getDialogPane();
        dialogPane.getButtonTypes().addAll(ButtonType.OK, ButtonType.CANCEL);
        TextField textField = new TextField("Name");
        DatePicker datePicker = new DatePicker(LocalDate.now());
        ObservableList<Venue> options =
            FXCollections.observableArrayList(Venue.values());
        ComboBox<Venue> comboBox = new ComboBox<>(options);
        SingleSelectionModel selectionModel = comboBox.getSelectionModel();
        selectionModel.selectFirst();
        TextField selection = new TextField(String.valueOf(selectionModel.getSelectedIndex()));
        selectionModel.selectedIndexProperty().addListener((Observable o) -> {
            selection.setText(String.valueOf(selectionModel.getSelectedIndex()));
        });
        Button clear = new Button("Clear");
        clear.setOnAction((action) -> {
            options.clear();
        });
        Button restore = new Button("Restore");
        restore.setOnAction((action) -> {
            options.clear();
            options.addAll(Venue.values());
            selectionModel.selectLast();
        });
        dialogPane.setContent(new VBox(8, textField, datePicker, comboBox, selection, clear, restore));
        Platform.runLater(textField::requestFocus);
        dialog.setResultConverter((ButtonType button) -> {
            if (button == ButtonType.OK) {
                return new Results(textField.getText(),
                    datePicker.getValue(), comboBox.getValue());
            }
            return null;
        });
        Optional<Results> optionalResult = dialog.showAndWait();
        optionalResult.ifPresent((Results results) -> {
            System.out.println(
                results.text + " " + results.date + " " + results.venue);
        });
    }

    private static enum Venue {Here, There, Elsewhere}

    private static class Results {

        String text;
        LocalDate date;
        Venue venue;

        public Results(String name, LocalDate date, Venue venue) {
            this.text = name;
            this.date = date;
            this.venue = venue;
        }
    }

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