java - togglegroup.getSelectedToogle() 始终返回 null JavaFX

Question

我有这段代码可以从选定的ToggleGroup中获取值。

但是，当我运行此代码时，我得到一个空列表。我似乎不知道如何解决这个问题。

   public TestPane(TestService service) {
        this.service = service;

        this.setPrefHeight(300);
        this.setPrefWidth(750);

        this.setPadding(new Insets(5, 5, 5, 5));
        this.setVgap(5);
        this.setHgap(5);

        questionField = new Label();
        vragen = service.getAllQuestions();
        Question question = vragen.iterator().next();
        questionField.setText(question.getQuestion());
        vragen.remove(question);

        add(questionField, 0, 0, 1, 1);

        statementGroup = new ToggleGroup();
        Set<String> statements = question.getStatements();
        System.out.println(statements);
        int i = 1;
        for (String st : statements) {
            radio = new RadioButton(st);
            radio.setText(st);
            radio.setUserData(st);
            radio.setToggleGroup((ToggleGroup) statementGroup.getUserData());
            add(radio, 0, i++);
        }

        submitButton = new Button("Submit");
        add(submitButton, 0, i);
        submitButton.setOnAction(new SubmitHandler(this,service));
    }

    public List<String> getSelectedStatements() {
        List<String> selected = new ArrayList<String>();
        if (statementGroup.getSelectedToggle() != null) {
            selected.add(statementGroup.getSelectedToggle().getUserData().toString());
        }
        return selected;
    }

Answer 1

以下行不正确:

radio.setToggleGroup((ToggleGroup) statementGroup.getUserData());

正确的调用是:

radio.setToggleGroup(statementGroup);

回答“为什么”的问题:ToggleGroup 的 getSelectedToggle 方法始终返回 null，因为没有与之关联的切换，如

(ToggleGroup) statementGroup.getUserData()

返回null，因此实际上会执行radio.setToggleGroup(null)，这意味着:RadioButton没有切换组。