JavaFX FXML - Add choices to choice box

Question

I am having a very tough time finding any documentation, so sorry in advance for the dumb question. I would like to populate a choice box that's declared with FXML with items that that are part of an ArrayList.

Here is my FXML:

Here is my controller:

package application;

import java.awt.Choice;
import java.net.URL;
import java.util.ArrayList;
import java.util.ResourceBundle;

import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.*;
import javafx.scene.control.MenuBar;
import javafx.scene.input.InputEvent;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyEvent;
import javafx.scene.input.MouseEvent;
import localMarketUpdate.*;

public class LMUController implements Initializable{

    LMUParser lmuParser;
    ChoiceBox choiceCity;

    @Override
    public void initialize(URL location, ResourceBundle resources) {

        lmuParser = new LMUParser();

    }

    @FXML
    private void btnCitiesRefresh_action(ActionEvent event)
    {
        ArrayList cities = lmuParser.getCities();
        ObservableList list = FXCollections.observableArrayList(cities);


        for (int i = 0; i < cities.size(); i++){

            list.add(i, cities.get(i));
            //list.add(i, cities.get(i));

        }

        choiceCity.setItems(FXCollections.observableArrayList("One","Two","Three"));
    }

}

I am getting an error on the line:

choiceCity.setItems(FXCollections.observableArrayList("One","Two","Three"));

Caused by: java.lang.NullPointerException at application.LMUController.btnCitiesRefresh_action(LMUController.java:47) ... 58 more

The ultimate goal here is to have the ChoiceBox by populated with the items in the ArrayList. How is this accomplished, and what am I doing wrong?

fabian · Accepted Answer

It should be done like this:

ArrayList cities = lmuParser.getCities();
ObservableList list = FXCollections.observableArrayList(cities);
choiceCity.setItems(list);

However for this to work the ChoiceBox actually has to be injected, which is not happening since you use the id attribute that assigns the Node's id property instead of using the id attribute from the fxml namespace. Also it would be a good idea to use a type parameter of ChoiceBox and use the private modifier:

@FXML
private ChoiceBox choiceCity;

FXML file:

add the namespace prefix of the fxml namespace to the id attribute of the ChoiceBox:

...

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JavaFX FXML - Add choices to choice box

Answers (1)

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