java - 每次选择新项目时打印选定的组合框项目

Question

我在 Controller 类中有一个组合框:

public class Controller {

    static String selectedCountry;

    @FXML
    private ResourceBundle resources;

    @FXML
    private URL location;

    @FXML
    private ComboBox<String> comboBoxCountries;

    @FXML
    void initialize() {
        assert comboBoxCountries != null : "fx:id=\"comboBoxCountries\" was not injected: check your FXML file 'app.fxml'.";

        comboBoxCountries.setItems(Main.COUNTRIES);

        selectedCountry = comboBoxCountries.getSelectionModel().getSelectedItem();

    }
}

在 Main 中，我想在控制台中打印所选项目。每次选择新项目时，如何打印新选择的值？

public class Main extends Application {
public static void main(String[] args) {
        launch(args);
 }

    @Override
    public void start(Stage stage) throws Exception {
        System.out.println(Controller.selectedCountry);
        Parent root= FXMLLoader.load(getClass().getResource("/fxml/app.fxml"));
        Scene scene = new Scene(root,1200,900);
        stage.setScene(scene);
        stage.show();
    }

Answer 1

只需向所选项目属性添加一个监听器:

comboBoxCountries.getSelectionModel().selectedItemProperty().addListener((observable, oldValue, newValue) -> {
    System.out.println(newValue);
});