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我在使用此代碼時遇到問題。變量結果應該從服務器的響應中填充，但由於某種原因，它會一直返回一個空字符串。讀取服務器發送的數據時出現空字符串
這是整個代碼：這裏
public class FragmentRally extends Fragment {
public FragmentRally() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_fragment_rally, container, false);
new AsyncFetch().execute();
return rootView;
}
// CONNECTION_TIMEOUT and READ_TIMEOUT are in milliseconds
public static final int CONNECTION_TIMEOUT = 10000;
public static final int READ_TIMEOUT = 15000;
private RecyclerView vistaRallye;
private AdapterRallye adaptadorRallye;
private class AsyncFetch extends AsyncTask<String, String, String> {
ProgressDialog pdLoading = new ProgressDialog(getActivity());
HttpURLConnection conn;
URL url = null;
@Override
protected void onPreExecute() {
super.onPreExecute();
//this method will be running on UI thread
pdLoading.setMessage("\tCarregant...");
pdLoading.setCancelable(false);
pdLoading.show();
}
@Override
protected String doInBackground(String... params) {
try {
// Enter URL address where your json file resides
// Even you can make call to php file which returns json data
url = new URL("http://www.rallyecat.esy.es/Obtenir_events.php");
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return e.toString();
}
try {
// Setup HttpURLConnection class to send and receive data from php and mysql
conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(READ_TIMEOUT);
conn.setConnectTimeout(CONNECTION_TIMEOUT);
conn.setRequestMethod("GET");
// setDoOutput to true as we recieve data from json file
conn.setDoOutput(true);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
return e1.toString();
}
try {
int response_code = conn.getResponseCode();
// Check if successful connection made
if (response_code == HttpURLConnection.HTTP_OK) {
// Read data sent from server
InputStream input = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(input));
StringBuilder result = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
// Pass data to onPostExecute method
return (result.toString());
} else {
return ("No hi ha connexió a internet.");
}
} catch (IOException e) {
e.printStackTrace();
return e.toString();
} finally {
conn.disconnect();
}
}
@Override
protected void onPostExecute(String result) {
//this method will be running on UI thread
pdLoading.dismiss();
List<DataRallye> data = new ArrayList<>();
pdLoading.dismiss();
try {
JSONArray jArray = new JSONArray(result);
// Extract data from json and store into ArrayList as class objects
for (int i = 0; i < jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
DataRallye dadesrallye = new DataRallye();
dadesrallye.RallyeNom = json_data.getString("nom");
dadesrallye.RallyeTipus = json_data.getString("tipus");
dadesrallye.RallyeDataI = json_data.getString("datai");
dadesrallye.RallyeDataF = json_data.getString("dataf");
dadesrallye.RallyeCiutat = json_data.getString("ciutat");
dadesrallye.RallyeOrganitzacio = json_data.getString("organitzacio");
dadesrallye.RallyeFoto = json_data.getString("foto");
data.add(dadesrallye);
}
// Setup and Handover data to recyclerview
vistaRallye = (RecyclerView) getView().findViewById(R.id.llistarallyes);
adaptadorRallye = new AdapterRallye(getActivity(), data);
vistaRallye.setAdapter(adaptadorRallye);
vistaRallye.setLayoutManager(new LinearLayoutManager(getActivity()));
} catch (JSONException e) {
Toast.makeText(getActivity(), e.toString(), Toast.LENGTH_LONG).show();
}
}
}
}
的問題出現：
// Read data sent from server
InputStream input = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(input));
StringBuilder result = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
// Pass data to onPostExecute method
return (result.toString());
這個變量，結果是這裏經過，在那裏我做了JSON解析。但因爲它是空的，它直接進入catch異常：
@Override
protected void onPostExecute(String result) {
//this method will be running on UI thread
pdLoading.dismiss();
List<DataRallye> data = new ArrayList<>();
pdLoading.dismiss();
try {
JSONArray jArray = new JSONArray(result);
// Extract data from json and store into ArrayList as class objects
for (int i = 0; i < jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
DataRallye dadesrallye = new DataRallye();
dadesrallye.RallyeNom = json_data.getString("nom");
dadesrallye.RallyeTipus = json_data.getString("tipus");
dadesrallye.RallyeDataI = json_data.getString("datai");
dadesrallye.RallyeDataF = json_data.getString("dataf");
dadesrallye.RallyeCiutat = json_data.getString("ciutat");
dadesrallye.RallyeOrganitzacio = json_data.getString("organitzacio");
dadesrallye.RallyeFoto = json_data.getString("foto");
data.add(dadesrallye);
}
// Setup and Handover data to recyclerview
vistaRallye = (RecyclerView) getView().findViewById(R.id.llistarallyes);
adaptadorRallye = new AdapterRallye(getActivity(), data);
vistaRallye.setAdapter(adaptadorRallye);
vistaRallye.setLayoutManager(new LinearLayoutManager(getActivity()));
} catch (JSONException e) {
Toast.makeText(getActivity(), e.toString(), Toast.LENGTH_LONG).show();
}
這裏是從我們的網站上的PHP文件生成的JSON：
[{"id_rally":"1","nom":"45e rallye costa brava","tipus":"velocitat i regularitat","datai":"2017-06-20","dataf":"2017-06-22","ciutat":"Girona","organitzacio":"rallyclassics ","foto":"brava.png"},{"id_rally":"2","nom":"26e rallye igualada","tipus":"velocitat","datai":"2017-08-13","dataf":"2017-08-16","ciutat":"Igualada","organitzacio":"ecb org","foto":"igualada.png"}]
'conn.setDoOutput（true）;'。刪除該行。 – greenapps
'result.append（line）;'這應該是'result.append（line）+「\ n」;' – greenapps
@greenapps解決了我的問題！萬分感謝！這條線是幹什麼的？謝謝！ –