java - 如何在Java中为ArrayList中的所有元素设置文本颜色？

Question

我以编程方式创建了 5 个单选组，每个组有 4 个单选按钮。每个单选按钮代表一个问题的答案。所以我想这样做。当有人检查 radio 组中的正确答案时，我想将所有答案添加到名为 CorrectAnswerRadios 的 ArrayList 中。与错误答案相同。我还在按钮上设置了一个 OnClickListener 。当有人按下按钮时，我还想将所有正确答案设为绿色，将错误答案设为红色。使用此代码，我收到此错误:“java.lang.NullPointerException:尝试写入空数组”。

这是我的代码:

RadioGroup[] answerGroup;
RadioButton[] answer;
Button finishButton;
RadioButton[] checkedRadioButton;
ArrayList<RadioButton> correctAnswerRadios;
ArrayList<RadioButton> wrongAnswersRadios;

    correctAnswerRadios = new ArrayList<>();
    wrongAnswersRadios = new ArrayList<>();
    answerGroup = new RadioGroup[5];
    answer = new RadioButton[4];

    int i = 0;
    for (Question qn : questions) {
        answerGroup[i] = new RadioGroup(this);
        int j = 0;
        for (Answer an : answers) {
            if (qn.getID() == an.getQuestion_id_answer()) {
                answer[j] = new RadioButton(this);
                answer[j].setText(an.getAnswer());
                answer[j].setId(j + 100);
                answer[j].setTag(String.valueOf(an.getCorrect_answer()));
                answerGroup[i].addView(answer[j]);

                answer[j].setOnClickListener(new View.OnClickListener() {
                    private boolean isChecked = true;
                    @Override
                    public void onClick(View v) {
                        for (int j = 0; j < answer.length; j++) {
                            checkedRadioButton[j] = ((RadioButton) v);
                            int CorrectAnswer = Integer.parseInt(checkedRadioButton[j].getTag().toString());
                            if (checkedRadioButton[j].isChecked() & CorrectAnswer == 1) {
                                correctAnswerRadios.add(checkedRadioButton[j]);
                            } else {
                                wrongAnswersRadios.add(checkedRadioButton[j]);
                            }
                        }
                    }
                });
                j++;
            }
        }
        linearLayout.addView(answerGroup[i]);
        i++;
    }

    finishButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            for (int i = 0; i < answerGroup.length; i++) {
                for (int j = 0; j < answer.length; j++) {
                    RadioButton correctRadio = correctAnswerRadios.get(j);
                    correctRadio.setTextColor(Color.GREEN);
                    RadioButton wrongRadio = wrongAnswersRadios.get(j);
                    wrongRadio.setTextColor(Color.RED);
                    answerGroup[i].getChildAt(j).setEnabled(false);
                }
            }
        }
    });

任何帮助将不胜感激。谢谢!

Answer 1

您需要初始化数组。例如:

checkedRadioButton = new RadioButton[size];