Java 如何显示问题和选项？

我正在开发一个Android应用程序，它需要显示一个问题（TextView）和四个可能的答案（带单选按钮的RadioGroup）。我使用Web服务器和MySql将数据库连接到我的应用程序中。为了获取数据，我在PHP中使用此方法将数据转换为JSON

<?php

include_once 'db.php';

class Quiz{

private $db;

private $db_table = "aenglish_questions";

    public function __construct(){

        $this->db = new DbConnect();

    }

    public function getAllQuizQuestions(){

        $json_array = array();

        $query = "select * from aenglish_questions";

        $result = mysqli_query($this->db->getDb(), $query);

            if(mysqli_num_rows($result) > 0){

                while ($row = mysqli_fetch_assoc($result)) {

            $json_array["quiz_questions"][] = $row;

                }

            }

        return $json_array;

    }

}

?>

---

如果您提出问题并添加所收到错误的堆栈跟踪，可能会有所帮助。您好，Abra爵士，我编辑了我的问题并发布了我收到的错误消息。请调试并检查您的回答是否包含数据引发异常的代码行是文件

Question10Fragment.java

中的第164行。看起来您调用了类

ArrayList

的方法

get（）

，但该列表为空。你需要调试你的代码，并试图发现为什么你的列表是空的。感谢各位的回复，我已经解决了我的问题，你们是最好的，直到下次。

private class AsyncJsonObject extends AsyncTask<String, Void, String> {

    private ProgressDialog progressDialog;

    @Override
    protected String doInBackground(String... params) {

        HttpClient httpClient = new DefaultHttpClient(new BasicHttpParams());
        HttpPost httpPost = new HttpPost("http://192.168.1.11/LETIA/includes/index.php");
        String jsonResult = "";

        try {
            HttpResponse response = httpClient.execute(httpPost);
            jsonResult = inputStreamToString(response.getEntity().getContent()).toString();
            System.out.println("Returned Json object " + jsonResult.toString());

        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return jsonResult;
    }
    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        progressDialog = ProgressDialog.show(getActivity(), "Downloading Quiz","Wait....", true);
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        progressDialog.dismiss();
        System.out.println("Resulted Value: " + result);
        parsedObject = returnParsedJsonObject(result);
        if(parsedObject == null){
            return;
        }
        quizCount = parsedObject.size();
        firstQuestion = parsedObject.get(0);

        quizQuestion.setText(firstQuestion.getQuestion());
        String[] possibleAnswers = firstQuestion.getAnswers().split(",");
        optionOne.setText(possibleAnswers[0]);
        optionTwo.setText(possibleAnswers[1]);
        optionThree.setText(possibleAnswers[2]);
        optionFour.setText(possibleAnswers[3]);
    }

    private StringBuilder inputStreamToString(InputStream is) {
        String rLine = "";
        StringBuilder answer = new StringBuilder();
        BufferedReader br = new BufferedReader(new InputStreamReader(is));

        try {
            while ((rLine = br.readLine()) != null) {
                answer.append(rLine);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return answer;
    }
}

    private List<QuizWrapper> returnParsedJsonObject(String result){

        List<QuizWrapper> jsonObject = new ArrayList<QuizWrapper>();
        JSONObject resultObject = null;
        JSONArray jsonArray = null;
        QuizWrapper newItemObject = null;

        try {
            resultObject = new JSONObject(result);
            System.out.println("Testing the water " + resultObject.toString());
            jsonArray = resultObject.optJSONArray("aenglish_questions");
        } catch (JSONException e) {
            e.printStackTrace();
        }
        for(int i = 0; i < jsonArray.length(); i++){
            JSONObject jsonChildNode = null;
            try {
                jsonChildNode = jsonArray.getJSONObject(i);
                int id = jsonChildNode.getInt("qae_id");
                String question = jsonChildNode.getString("question");
                String answerOptions = jsonChildNode.getString("choices");
                int correctAnswer = jsonChildNode.getInt("answer");
                newItemObject = new QuizWrapper(id, question, answerOptions, correctAnswer);
                jsonObject.add(newItemObject);
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
        return jsonObject;
    }

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.pre_boardreviewer, PID: 26290
    java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
        at java.util.ArrayList.get(ArrayList.java:437)
        at com.example.recall.EnglishFragments.Question10Fragment$AsyncJsonObject.onPostExecute(Question10Fragment.java:164)
        at com.example.recall.EnglishFragments.Question10Fragment$AsyncJsonObject.onPostExecute(Question10Fragment.java:123)
        at android.os.AsyncTask.finish(AsyncTask.java:695)
        at android.os.AsyncTask.access$600(AsyncTask.java:180)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:712)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7156)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975)