Question

我正在尝试从服务器获取数据并将其显示在我的应用中。但是，我从服务器获取结果为null。是否有可能结果为空并且无法从服务器获取数据？

这是我服务器的数据

{
"COLUMNS":    ["TIMEID","BRANCHID","COMPANYID","MON_O","TUE_O","WED_O","THU_O","FRI_O","SAT_O","SUN_O","MON_C","TUE_C","WED_C","THU_C","FRI_C","SAT_C","SUN_C","CREATDATE"],
"DATA":   
[[195,4,4,"09:00","09:00","09:00","09:00","09:00","Closed","Closed","16:30","16:30","16:30","16:30","16:30","Closed","Closed","May, 16 2017 08:16:12"]
]}

这就是我尝试获取数据的方式，

TextView timeStatus;

public static final String MON_O  = "MON_O";
public static final String TUE_O = "TUE_O";
public static final String WED_O = "WED_O";
public static final String THU_O = "THU_O";
public static final String FRI_O = "FRI_O";
public static final String SAT_O = "SAT_O";
public static final String SUN_O = "SUN_O";

public static final String MON_C = "MON_C";
public static final String TUE_C = "TUE_C";
public static final String WED_C = "WED_C";
public static final String THU_C = "THU_C";
public static final String FRI_C = "FRI_C";
public static final String SAT_C = "SAT_C";
public static final String SUN_C = "SUN_C";

public static final String JSON_ARRAY = "COLUMNS";

timeStatus = (TextView) view.findViewById(R.id.time_status);

单击RelativeLayout，调用getData（）函数，

            timeLayout.setOnClickListener(new View.OnClickListener() {

                 @Override
                   public void onClick(View v) {
                    if (timeLayoutCollapse.getVisibility() == View.GONE) {
                        timeLayoutCollapse.setVisibility(View.VISIBLE);
                            getData();
                        } else {
                            timeLayoutCollapse.setVisibility(View.GONE);
                        }
                    }
                });

和JSON Response函数如下，

private void getData() {

    if (dBranchID == 0) {

        Log.e("no branch id", "sdsfsdf");
        return;
    }


    String url = context.getString(site_url)+"branch_time.cfc?method=branchtime&branchid=" +dBranchID;

    StringRequest stringRequest = new StringRequest(url, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            showJSON(response);
        }
    },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    Toast.makeText(context,error.getMessage().toString(),Toast.LENGTH_LONG).show();
                }
            });

    RequestQueue requestQueue = Volley.newRequestQueue(context);
    requestQueue.add(stringRequest);
}



private void showJSON(String response) {

    String name = "";
    String address = "";
    String vc = "";


    try {
        JSONObject jsonObject = new JSONObject(response);
        JSONArray result = jsonObject.getJSONArray(JSON_ARRAY);
        JSONObject companyData = result.getJSONObject(0);

        mon = companyData.getString(MON_O);
        tue = companyData.getString(TUE_O);
        wed = companyData.getString(WED_O);
    } catch (JSONException e) {
        e.printStackTrace();
    }
    timeStatus.setText(mon);
}

我收到错误，

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference.

Answer 1

问题出在这里。你得到的是timestatus的空值。修复它。

  timeStatus.setText(mon);

Answer 2

您的timestatus textview为null 请转换（findviewbyid）timestatus，或者你可以在doinbackground中调用该方法。如果你把那个metod放在doinbackground中，那么它会给出空指针异常

从服务器获取数据时出错java.lang.NullPointerException：Android

2 个答案: