オンライン回答質問における回答記録のバックアップおよび同期機能を実装する方法

CREATE TABLE answer_records (
    student_id INT NOT NULL,
    question_id INT NOT NULL,
    answer VARCHAR(255),
    score FLOAT,
    PRIMARY KEY (student_id, question_id)
);

class AnswerRecordDAO {
    private $conn;  // 数据库连接对象

    public function __construct() {
        // 连接数据库
        $this->conn = new mysqli("localhost", "username", "password", "database");
        if ($this->conn->connect_error) {
            die("数据库连接失败：" . $this->conn->connect_error);
        }
    }

    public function insertAnswerRecord($studentId, $questionId, $answer, $score) {
        $stmt = $this->conn->prepare("INSERT INTO answer_records (student_id, question_id, answer, score) VALUES (?, ?, ?, ?)");
        $stmt->bind_param("iisd", $studentId, $questionId, $answer, $score);
        $stmt->execute();
        $stmt->close();
    }

    public function updateAnswerRecord($studentId, $questionId, $answer, $score) {
        $stmt = $this->conn->prepare("UPDATE answer_records SET answer = ?, score = ? WHERE student_id = ? AND question_id = ?");
        $stmt->bind_param("sdii", $answer, $score, $studentId, $questionId);
        $stmt->execute();
        $stmt->close();
    }

    public function getAnswerRecord($studentId, $questionId) {
        $stmt = $this->conn->prepare("SELECT answer, score FROM answer_records WHERE student_id = ? AND question_id = ?");
        $stmt->bind_param("ii", $studentId, $questionId);
        $stmt->execute();
        $stmt->bind_result($answer, $score);
        $stmt->fetch();
        $stmt->close();

        $record = array("answer" => $answer, "score" => $score);
        return $record;
    }
    
    // ...其他方法
}

$answerRecordDAO = new AnswerRecordDAO();
$answerRecordDAO->insertAnswerRecord($studentId, $questionId, $answer, $score);

class AnswerRecordSyncTask extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... voids) {
        // 从服务器端获取答题记录
        String url = "http://example.com/get_answer_record.php";
        HttpClient client = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(url);
        HttpResponse response;

        try {
            response = client.execute(httpGet);
            HttpEntity entity = response.getEntity();
            String jsonString = EntityUtils.toString(entity);

            // 将答题记录保存到本地
            SharedPreferences sharedPreferences = getSharedPreferences("answer_record", MODE_PRIVATE);
            SharedPreferences.Editor editor = sharedPreferences.edit();
            editor.putString("answer", jsonString);
            editor.apply();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }
}

// 调用答题记录同步任务
new AnswerRecordSyncTask().execute();