我初学者在android开发中，在下面的代码中得到错误。我已经看过和其他相关的帖子，我明白错误是在doInBackground方法而且理解和发生错误，但我无法理解哪个地方代码我必须改变
我的班级
public class FetchDrugTask extends AsyncTask<String, Void, JSONArray> {
public ItemListScreen listScreen = null;
private static final String TAG_DRUGS = "drugs";
private static final String KEY_DRUGID = "id";
private static final String KEY_DESCRIPTION = "description";
private static final String KEY_PRESCRIPTION= "prescription";
static final String KEY_NAME= "name";
JSONArray drugs = null;
@Override
protected JSONArray doInBackground(String... urls) {
HttpClient client = new DefaultHttpClient();
HttpGet get = new HttpGet(urls[0]);
String responseBody = "{}";
try {
HttpResponse response = client.execute(get);
responseBody = getResponseBody(response);
}
catch (Exception ex) {
ex.printStackTrace();
}
try {
JSONObject json = new JSONObject(responseBody);
drugs = json.getJSONArray(TAG_DRUGS);
return drugs;
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(JSONArray todoJsonArray) {
//List<BusItem> routeItems = new ArrayList<BusItem>();
ArrayList<HashMap<String, String>> drugList = new ArrayList<HashMap<String, String>>();
for (int i = 0; i < todoJsonArray.length(); i++) {
try {
HashMap<String, String> map = new HashMap<String, String>();
JSONObject jsonObject = todoJsonArray.getJSONObject(i);
map.put(getKeyDrugid(), jsonObject.getString(getKeyDrugid()));
map.put(getKeyDescription(), jsonObject.getString(getKeyDescription()));
map.put(getKeyPrescription(), jsonObject.getString(getKeyPrescription()));
map.put(getKeyName(), jsonObject.getString(getKeyName()));
// adding HashList to ArrayList
drugList.add(map);
// routeItems.add(new BusItem(jsonObject.getString("bus_id"),jsonObject.getString("latitude"),jsonObject.getString("longitude")));
Log.i("FETCHING DATA", jsonObject.getString(getKeyDrugid()));
} catch (JSONException e) {
e.printStackTrace();
}
}
listScreen.displayList(drugList);
}
public static String getKeyName() {
return KEY_NAME;
}
private String getResponseBody(HttpResponse response) {
StringBuilder builder = new StringBuilder();
try {
InputStream body = response.getEntity().getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(body));
String line;
while ((line = reader.readLine()) != null) {
builder.append(line);
}
return builder.toString();
} catch (IOException e) {
e.printStackTrace();
return "{}";
}
}
public static String getKeyDrugid() {
return KEY_DRUGID;
}
public static String getKeyDescription() {
return KEY_DESCRIPTION;
}
public static String getKeyPrescription() {
return KEY_PRESCRIPTION;
}
}
我的JSOn
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "utf-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
Log.e("JSON", json);
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
List<NameValuePair> params) {
// Making HTTP request
try {
// check for request method
if (method == "POST") {
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} else if (method == "GET") {
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "utf-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
错误
10-29 18:42:09.857: E/AndroidRuntime(24733): FATAL EXCEPTION: AsyncTask #1
10-29 18:42:09.857: E/AndroidRuntime(24733): Process: com.drugfinder, PID: 24733
10-29 18:42:09.857: E/AndroidRuntime(24733): java.lang.RuntimeException: An error occured while executing doInBackground()
10-29 18:42:09.857: E/AndroidRuntime(24733): at android.os.AsyncTask$3.done(AsyncTask.java:300)
10-29 18:42:09.857: E/AndroidRuntime(24733): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
10-29 18:42:09.857: E/AndroidRuntime(24733): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
10-29 18:42:09.857: E/AndroidRuntime(24733): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
10-29 18:42:09.857: E/AndroidRuntime(24733): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
10-29 18:42:09.857: E/AndroidRuntime(24733): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
10-29 18:42:09.857: E/AndroidRuntime(24733): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
10-29 18:42:09.857: E/AndroidRuntime(24733): at java.lang.Thread.run(Thread.java:841)
10-29 18:42:09.857: E/AndroidRuntime(24733): Caused by: java.lang.RuntimeException: org.json.JSONException: End of input at character 0 of
10-29 18:42:09.857: E/AndroidRuntime(24733): at com.drugfinder.library.FetchStoreTask.doInBackground(FetchStoreTask.java:57)
10-29 18:42:09.857: E/AndroidRuntime(24733): at com.drugfinder.library.FetchStoreTask.doInBackground(FetchStoreTask.java:1)
10-29 18:42:09.857: E/AndroidRuntime(24733): at android.os.AsyncTask$2.call(AsyncTask.java:288)
10-29 18:42:09.857: E/AndroidRuntime(24733): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
10-29 18:42:09.857: E/AndroidRuntime(24733): ... 4 more
10-29 18:42:09.857: E/AndroidRuntime(24733): Caused by: org.json.JSONException: End of input at character 0 of
10-29 18:42:09.857: E/AndroidRuntime(24733): at org.json.JSONTokener.syntaxError(JSONTokener.java:450)
10-29 18:42:09.857: E/AndroidRuntime(24733): at org.json.JSONTokener.nextValue(JSONTokener.java:97)
10-29 18:42:09.857: E/AndroidRuntime(24733): at org.json.JSONObject.<init>(JSONObject.java:155)
10-29 18:42:09.857: E/AndroidRuntime(24733): at org.json.JSONObject.<init>(JSONObject.java:172)
10-29 18:42:09.857: E/AndroidRuntime(24733): at com.drugfinder.library.FetchStoreTask.doInBackground(FetchStoreTask.java:50)
10-29 18:42:09.857: E/AndroidRuntime(24733): ... 7 more
Thnx提前