Question

我正在尝试获取故障单响应并将其显示在自定义列表视图中。问题是，如果票证存在并从服务器获得此类响应，它将完美显示列表，但是当没有票证且服务器响应为Status:failed Msg:No ticket available时。

以下是我的代码：

 class viewticket extends AsyncTask<String, Void, String> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pdialog = new ProgressDialog(UserLogedIn.this);
        pdialog.setMessage("Loading....");
        pdialog.setIndeterminate(false);
        pdialog.setCancelable(false);
        pdialog.show();
    }

    @Override
    protected String doInBackground(String... params)  {
        List<NameValuePair> param = new ArrayList<NameValuePair>();
        param.add(new BasicNameValuePair("userid", u_id));
       // JSONObject jsonArray = jpar.makeHttpRequest(URLMyTicket, "POST", param);

        ServiceHandler sh = new ServiceHandler();


        String jsonStr = sh.makeServiceCall(URLMyTicket, ServiceHandler.POST, param);
        Log.d("Response: ", "> " + jsonStr);
        if (jsonStr != null)

        {
            try {

                contacts = new JSONArray(jsonStr);
                 a=contacts.length();
                Log.v(TAG,""+a);
                if(a > 0 )
                {


                id = new String[contacts.length()];

                 prob = new String[contacts.length()];
                desc = new String[contacts.length()];
                for (int i = 0; i < contacts.length(); i++) {
                    JSONObject c = contacts.getJSONObject(i);

                    String aa = c.getString(TAG_ID);
                    String bb = c.getString(TAG_PROB);
                    String cc = c.getString(TAG_DESC);

                    Log.v(TAG, "TAG_ID" + aa);
                    Log.v(TAG, "TAGPROB" + bb);
                    Log.v(TAG, "TAGDESC" + cc);
                    id[i] = aa;
                    prob[i] = bb;
                    desc[i] = cc;
                    Log.v(TAG, "aaaaa" + id[i]);
                    Log.v(TAG, "bbbbb" + prob[i]);
                    Log.v(TAG, "ccc" + desc[i]);
                }
                }

            } catch (JSONException e) {
              System.out.print("hiiiiiiiiiiii" );
                e.printStackTrace();
            }
        }

        return null;
    }
    @Override
    protected void onPostExecute(String  result) {
        super.onPostExecute(result);
        // Dismiss the progress dialog
        Log.v(TAG,"length of aaaaa"+a);
        if(id.length > 0 )//i will get error if ticket is not present Attempt to get length of null array
        {
            Ticket_adapter adapter=new Ticket_adapter(UserLogedIn.this,id,prob,desc);
            lv.setAdapter(adapter);
        }
        else
        {
            Toast.makeText(UserLogedIn.this, "No Ticket Present", Toast.LENGTH_SHORT).show();
        }
        pdialog.hide();
        pdialog.dismiss();



    }

   }

如果票证不存在，我会收到以下错误

处理：com.example.surun.suruninfocore，PID：22673 java.lang.NullPointerException：尝试获取null数组的长度 at com.example.surun.suruninfocore.UserLogedIn $ viewticket.onPostExecute（UserLogedIn.java:791） at com.example.surun.suruninfocore.UserLogedIn $ viewticket.onPostExecute（UserLogedIn.java:720）

见第791行：

if (id.length > 0)

和第720行：

class viewticket extends AsyncTask<String, Void, String> {

Answer 1

Change your if condition to id!=null && id.length > 0
protected void onPostExecute(String  result) {
        super.onPostExecute(result);
        // Dismiss the progress dialog
        Log.v(TAG,"length of aaaaa"+a);
        if(id!=null && id.length > 0 )//i will get error if ticket is not present Attempt to get length of null array
        {
            Ticket_adapter adapter=new Ticket_adapter(UserLogedIn.this,id,prob,desc);
            lv.setAdapter(adapter);
        }
        else
        {
            Toast.makeText(UserLogedIn.this, "No Ticket Present", Toast.LENGTH_SHORT).show();
        }
        pdialog.hide();
        pdialog.dismiss();



    }

服务器给我显示自定义列表视图

1 个答案: