Question

我尝试使用JsonArrayRequest检索json数据，然后将其添加到列表中。这是我的代码

public class QuestionDetailFragment extends Fragment {
    RecyclerView cRecyclerView;
    private static final String url = "http://10.0.2.2:80/forumtest/readquestion.php?format=json";
    private List<String> userList = new ArrayList<>();
    RequestQueue requestQueue;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.question_details_layout, container, false);
        readQuestionDetails();

        Log.d("check", "data:" + userList.get(0));

        return view;
    }

    private void readQuestionDetails() {
        Log.d("Volley", "Called222!");
        requestQueue = Volley.newRequestQueue(getActivity().getApplicationContext());
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.POST, url, new Response.Listener<JSONArray>() {
            @Override
            public void onResponse(JSONArray response) {

                try {
                    for (int i=0;i<response.length();i++) {
                        JSONObject jsonObject = response.getJSONObject(i);

                        userList.add(jsonObject.getString("user"));

                            }

                } catch (JSONException e) {
                    e.printStackTrace();
                    Log.e("tag",e.getMessage());
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e("Volley", error.getMessage());

            }
        });


        requestQueue.add(jsonArrayRequest);
    }

}

我使用了 Log.d（＆＃34;用户`，＆＃34;数据：＆＃34;，user.get（0））; < / strong>只是为了确保数据已添加到列表中。这是我运行代码后的logcat

03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: FATAL EXCEPTION: main 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: Process: com.rekoj.softwarica, PID: 2767 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at java.util.ArrayList.get(ArrayList.java:308) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at com.rekoj.softwarica.Forum.QuestionDetailFragment.onCreateView(QuestionDetailFragment.java:50) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.os.Handler.handleCallback(Handler.java:739) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:95) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.os.Looper.loop(Looper.java:148) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5417) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 03-08 20:45:25.750 2767-2767/com.rekoj.softwarica E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 03-08 20:50:25.802 2767-2767/? I/Process: Sending signal. PID: 2767 SIG: 9

Answer 1

堆栈跟踪指出列表userList为空，这就是您获得IndexOutOfBoundsException的原因，readQuestionDetails中的获取逻辑是异步执行的。

Answer 2

把这一行

Log.d("check", "data:" + userList.get(0));

以下

userList.add(jsonObject.getString("user"));
Log.d("check", "data:" + userList.get(0));

这是因为下面这两个方法调用在不同的线程中运行

readQuestionDetails();
Log.d("check", "data:" + userList.get(0));

致命异常：索引0无效，满分为0

2 个答案: