我在www文件夹中添加了questions.json文件，我正在尝试检索它。
问题响应总是返回null我猜这个例外是httpClient.execute(httpGet);，但不确定
@SuppressLint("NewApi")
public class QuestionListFragment extends android.app.ListFragment
{
private ProgressDialog pDialog;
// url to make request
private static String url = "http://localhost/questions.json";
// JSON Node names
private static final String TAG_QUESTIONS = "Questions";
private static final String TAG_ID = "Question_Id";
private static final String TAG_BODY = "QuestionBody";
private static final String TAG_TITLE = "QuestionTitle";
private static final String TAG_NAME = "Asker_Name";
private static final String TAG_TIME = "Created At";
private static final String TAG_ANSWERS = "Answers";
private static final String TAG_ANSWER = "answer";
private static final String TAG_A_NAME = "Name";
private static final String TAG_RATING = "Rating";
// questions JSONArray
JSONArray questions = null;
ListView lv;
Context c;
JSONObject obj ;
ArrayList<HashMap<String, String>> questionsList = new ArrayList<HashMap<String, String>>();
@Override
public View onCreateView( LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState )
{
View view = inflater.inflate(ask.code.R.layout.questions_list_frag, container, false);
new GetQuestions().execute();
return view;
}
private class GetQuestions extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try{
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
questions = jsonObj.getJSONArray(TAG_QUESTIONS);
// looping through All Questions
for(int i = 0; i < questions.length(); i++){
JSONObject c = questions.getJSONObject(i);
String id = c.getString(TAG_ID);
String title = c.getString(TAG_TITLE);
String body = c.getString(TAG_BODY);
String name = c.getString(TAG_NAME);
String time = c.getString(TAG_TIME);
JSONObject answers = c.getJSONObject(TAG_ANSWERS);
String answer = answers.getString(TAG_ANSWER);
String a_name = answers.getString(TAG_A_NAME);
String a_rating = answers.getString(TAG_RATING);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
map.put(TAG_TITLE, title);
map.put(TAG_BODY, body);
// adding HashList to ArrayList
questionsList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
getActivity(),
questionsList,
ask.code.R.layout.question_item,
new String[] {
TAG_NAME,
TAG_TITLE,
TAG_TIME},
new int[] {
ask.code.R.id.asker_name,
ask.code.R.id.question_title,
ask.code.R.id.question_rating});
setListAdapter(adapter);
}
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
// TODO Auto-generated method stub
super.onListItemClick(l, v, position, id);
}
// TODO Auto-generated method stub
}
的ServiceHandler
public class ServiceHandler {
static String response = null;
public final static int GET = 1;
public final static int POST = 2;
public ServiceHandler() {
}
/**
* Making service call
* @url - url to make request
* @method - http request method
* */
public String makeServiceCall(String url, int method) {
return this.makeServiceCall(url, method, null);
}
/**
* Making service call
* @url - url to make request
* @method - http request method
* @params - http request params
* */
public String makeServiceCall(String url, int method,
List<NameValuePair> params) {
try {
// http client
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpEntity httpEntity = null;
HttpResponse httpResponse = null;
// Checking http request method type
if (method == POST) {
HttpPost httpPost = new HttpPost(url);
// adding post params
if (params != null) {
httpPost.setEntity(new UrlEncodedFormEntity(params));
}
httpResponse = httpClient.execute(httpPost);
} else if (method == GET) {
// appending params to url
if (params != null) {
String paramString = URLEncodedUtils
.format(params, "utf-8");
url += "?" + paramString;
}
HttpGet httpGet = new HttpGet(url);
httpResponse = httpClient.execute(httpGet);
}
httpEntity = httpResponse.getEntity();
response = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return response;
}
}
questions.json
{
"Questions": [
{
"CreatedAt": "2013-07-31T09: 57: 34.618Z",
"Asker_Name": "Cloyd",
"QuestionTitle": "temporadoloremquevoluptatemestquisquamundevoluptatemsuntearum\nsitfugaducimusnequeomnisin\npariaturminusdebitisquaeratrerumnamvelitveritatisrem",
"QuestionBody": "voluptatemtemporadignissimosanimivelitdelectusconsequaturcumquedeserunt\nillumaperiamquisminimaeumremveniam\nutnumquamdoloremconsequaturvoluptatemofficiaveniam\nutarchitectoiddelenitiuteiuscumpossimus\ndolorumprovidentmollitianullarerum\n\r\tquiainarchitectodebitislaboreerror\nvoluptatibussitquaeratdoloreassumendadoloremdoloresconsectetur\nsedetevenietsaepeconsequaturvelarchitecto\n\r\tdolorumvoluptatemquaevoluptatebeatae\ndoloremqueutofficiisquibusdamiustopariaturiureautdolorem\nidquialiquideosvelet",
"Question_Id": 0,
"Answers": {
"Answer": "temporakdjd",
"Name": "saleem",
"Rating": "10"
}
},
{
"CreatedAt": "1997-08-05T20: 13: 37.888Z",
"Asker_Name": "Alexander",
"QuestionTitle": "fugaetnequequoettemporibus\natvoluptatumessesit\nnullaadipisciquaeducimus",
"QuestionBody": "quiainciduntetquoserror\ncumqueetautsitidexcepturiaccusantiumpariaturconsequatur\nlaudantiummaioressedillomagniexplicabo\nindolorprovidentvoluptasearumdelenitidelectusmollitia\n\r\tsapienteinnemo\nexpeditaautinnon\nprovidentabveniamut\n\r\tenimducimussuntrerumnamsed\nsaepepraesentiumaliquamverolaborumdeseruntidex\nautsedvelittemporibusexplicaboveniamvoluptatemin\nisteetutnobisprovidentasperiores\nexpeditaitaqueullam",
"Question_Id": 1,
"Answers": {
"Answer": "temporakdjd",
"Name": "saleem",
"Rating": "10"
}
},
{
"CreatedAt": "1990-02-16T06: 37: 46.327Z",
"Asker_Name": "Kade",
"QuestionTitle": "nisidelectusasperioresveletidtempore\nrationeautautet\neaquenisiestrerumodioasperiorescupiditate",
"QuestionBody": "exrepellendusliberoeosautemetdictaautemsed\nabconsequaturetsitvoluptatemassumendavelitsint\nautconsequaturveniamodioquodoloremdolorem\neligendirerumexplicaboquiquiadolorem\n\r\tminusvoluptatemnamvelcupiditateaperiamsedrerumearum\nautrepudiandaeeavelsitreprehenderiteterrorfugiat\nsedeaquidemveritatisiure\n\r\tdoloremqueidsuntatquiacorruptimolestiaeexpeditavoluptate\nnontemporevelitestrepellendus\nessequaeinsit\nporronihilfacereautnecessitatibusquosunt\natlaborumatemporaullam",
"Question_Id": 2,
"Answers": {
"Answer": "temporakdjd",
"Name": "saleem",
"Rating": "10"
}
},
{
"CreatedAt": "1987-02-28T20: 39: 36.422Z",
"Asker_Name": "Madaline",
"QuestionTitle": "omnisnesciuntexcepturieligendirerumquam\netmolestiasfugiatremvoluptasvelitautet\nsedoccaecatidelectuseoset",
"QuestionBody": "inciduntquosbeataevoluptasidcommodideseruntexvero\netitaquemollitialaborumnemosedvoluptatibusperferendisdoloremque\nestsuscipitnonveniamutquaeaperiam\nveroetquiaautillo\nasperioressimiliquetempora\n\r\tvoluptatemaccusantiumconsequunturetconsequaturrepellataut\naspernaturnesciunteavoluptasnatusmaxime\nmaioresatconsequaturnequereiciendis\nadipiscienimrationeipsummagnamveniamsed\n\r\treiciendisutundequi\naperiamcorporisnesciuntid\nculpaetreprehenderittemporibusofficiaplaceataccusantiumcum\nquassitmaioresdelectusesse\nconsequaturtotamdolor",
"Question_Id": 3,
"Answers": {
"Answer": "temporakdjd",
"Name": "saleem",
"Rating": "10"
}
},
{
"CreatedAt": "1991-11-22T12: 50: 21.965Z",
"Asker_Name": "Lizzie",
"QuestionTitle": "quiaremnatus\nnatusofficiisquamomnisquifuga\nquiasitavoluptatem",
"QuestionBody": "quisvoluptasquilaborumsednostrumfugaea\nipsumquaeratveritatis\nporrouterrorex\nauteiusexplicabononfugaadutvoluptatumnihil\nabnoninarchitectocommodiminusquasanimi\n\r\tenimdebitisbeataemollitiadoloresiureiustoquia\ncommodiquiapossimusatemporibus\nidutnobisvoluptatumfugaaccusamusharum\netdictaquiamollitiaaccusamuspossimusvoluptatibusautalias\nautemdoloremnamaliquam\n\r\tsitdeseruntautestexcepturiquasi\nquibusdamevenietexcepturiducimusquosdicta\nearumsitenimautquisquamaliquam\nmagnamnesciuntinciduntvelitarchitectoomnis\nomnisminimaerrorfuga",
"Question_Id": 4,
"Answers": {
"Answer": "temporakdjd",
"Name": "saleem",
"Rating": "10"
}
},
{
"CreatedAt": "1987-05-09T15: 46: 08.048Z",
"Asker_Name": "Colleen",
"QuestionTitle": "rerumetaccusamussedabdolorenonest\nestperspiciatisquisedsintmolestiaeautcorporisomnis\nperferendisvelenim",
"QuestionBody": "iustomolestiasrerummollitiafacilisatquecumque\neumquaeatqueaspernaturadoloresestomnis\ndolornihilexcepturinecessitatibus\n\r\tidveniamevenietquifugiat\nreprehenderiterrornumquamautetquiquiarerum\ndolorummaximequasicorporismodiin\neosnostrumutsapientedoloremque\nquaeratconsequunturveniamperferendisautnisidoloresnonest\n\r\tquisuscipitadconsequaturrepellatvoluptatemmollitia\nquidemverocum\nmodidelenitivoluptasadipisciodio",
"Question_Id": 5,
"Answers": {
"Answer": "temporakdjd",
"Name": "saleem",
"Rating": "10"
}
},
{
"CreatedAt": "2002-05-04T05: 31: 45.704Z",
"Asker_Name": "Carlotta",
"QuestionTitle": "impeditquodillumconsequunturlabore\nsitundeblanditiisitaqueiustoutcorporisut\ndeseruntquasquam",
"QuestionBody": "illumevenietdolor\ndoloribusdistinctiorerumvoluptatumquibusdamest\ndoloremquevoluptassitautemeos\nexcepturiquieasuntverodictaatque\n\r\tisteullamut\nanimivoluptasautdoloresoccaecatiuttenetur\neaimpeditautaquispossimusperspiciatisestaccusantium\nutconsequaturminimabeataemolestiae\ndoloresdolorethic\n\r\tquisquamquidempariaturassumendalaborumveritatisquasdolore\ncommodiquaedebitisipsafugitcorporissitharumquam\nvoluptasbeataeeaetetutaperiam\naiurenihilnamnonaut\ndoloresprovidenthicetveroautmagnimaximelabore",
"Question_Id": 6,
"Answers": {
"Answer": "temporakdjd",
"Name": "saleem",
"Rating": "10"
}
}
]
}
答案 0 :(得分：1)
如果您使用的是模拟器，那么您必须编写10.0.2.2来代替localhost。 如果您使用的是设备，则必须连接到同一网络，并且必须将localhost替换为您的计算机IP地址。
我希望这会有所帮助
答案 1 :(得分：1)
您正尝试通过将localhost指定为托管服务的系统的地址来连接到服务器。 Android模拟器在虚拟机（QEMU）内运行。因此，localhost将是模拟器自己的环回地址，而不是系统的地址。
因此，您可以转到Windows中的CommandPrompt获取系统的IP地址，或者只使用http://10.0.2.2:8080/...而不是localhost。
<强> private static String url = "http://10.0.2.2:8080/questions.json";
答案 2 :(得分：0)
public String makeServiceCall(String url, int method,
List<NameValuePair> params) {
StringBuilder result = new StringBuilder();
try {
//URL urlObj = new URL(url);
URL urlObj = new URL(url.replace(" ","%20"));
urlConnection = (HttpURLConnection) urlObj.openConnection();
InputStream in = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
}catch( Exception e) {
e.printStackTrace();
}
finally {
urlConnection.disconnect();
}
return result.toString();
}
答案 3 :(得分：0)
这可能会有所帮助：
public class ServiceHandler {
static String response = null;
public final static int GET = 1;
public final static int POST = 2;
HttpURLConnection urlConnection;
public ServiceHandler() {
}
public String makeServiceCall(String url, int method) {
return this.makeServiceCall(url, method, null);
}
public String makeServiceCall(String url, int method,
List<NameValuePair> params) {
StringBuilder result = new StringBuilder();
try {
//URL urlObj = new URL(url);
URL urlObj = new URL(url.replace(" ","%20"));
urlConnection = (HttpURLConnection) urlObj.openConnection();
InputStream in = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
}catch( Exception e) {
e.printStackTrace();
}
finally {
urlConnection.disconnect();
}
return result.toString();
}
}