调用 Web 服务时出现空指针异常。该服务提供 Json 数组，如下所示：
[{"userid":210,
"name" :"Karan",
"email":"ka@gmail.com",
"password":"ka123456",
"created_at":"17-Oct-2013",
"success" : 1
}]
这是完成解析的类：
package library;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.os.AsyncTask;
import android.util.Log;
public class JSONParser extends AsyncTask<String, String, JSONObject> {
List<NameValuePair> postparams = new ArrayList<NameValuePair>();
String URL = null;
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {
this.URL = url;
this.postparams = params;
return null;
}
@Override
protected JSONObject doInBackground(String... params) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(URL);
httpPost.setEntity(new UrlEncodedFormEntity(postparams));
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();
}
return jObj;
}
protected JSONObject onPostExecute(String json) {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 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 JSONArray(json).getJSONObject(0);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
发生空指针异常错误的注册类
else
{
erName.setText("");
erPass.setText("");
erEmail.setText("");
erCopass.setText("");
UserFunction userFunction = new UserFunction();
JSONObject jObj = userFunction.registerUser(name, email, password);
// check for login response
try {
if (jObj.getString(KEY_SUCCESS) != null) {
String res = jObj.getString(KEY_SUCCESS);
if(Integer.parseInt(res) == 1){
// user successfully registred
// Store user details in SQLite Database
Databasehandler db = new Databasehandler(getApplicationContext());
JSONObject json_user = jObj.getJSONObject("userid");
// Clear all previous data in database
userFunction.logoutUser(getApplicationContext());
db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json_user.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));
// Launch Dashboard Screen
Intent login = new Intent(getApplicationContext(), LoginActivity.class);
// Close all views before launching Dashboard
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
// Close Registration Screen
Toast.makeText(RegisterActivity.this,"You are Registered successfully",Toast.LENGTH_SHORT).show();
finish();
}else{
// Error in registration
Toast.makeText(RegisterActivity.this,"User Allready Registered!!!",Toast.LENGTH_LONG).show();
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
错误发生在以下行： if (jObj.getString(KEY_SUCCESS) != null)
这是使用解析器作为后台任务的相关类
package library;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONObject;
import android.content.Context;
public class UserFunction {
private JSONParser jsonParser;
// Testing in localhost using wamp or xampp
// use http://10.0.2.2/ to connect to your localhost ie http://localhost/
private static String loginURL = "http://192.168.1.120/rvAndroidServices.ashx";
private static String registerURL = "http://192.168.1.120/rvAndroidServices.ashx";
private static String name1 = "http://192.168.1.120/rvAndroidServices.ashx";
private static String login_tag = "login";
private static String register_tag = "register";
private static String name_tag = "name";
// constructor
public UserFunction(){
jsonParser = new JSONParser();
}
/**
* function make Login Request
* @param email
* @param password
* */
public JSONObject loginUser(String email, String password){
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("tag", login_tag));
params.add(new BasicNameValuePair("email", email));
params.add(new BasicNameValuePair("password", password));
JSONObject jObj = jsonParser.getJSONFromUrl(loginURL, params);
// return json
// Log.e("JSON", json.toString());
return jObj;
}
/**
* function make Login Request
* @param name
* @param email
* @param password
* */
public JSONObject registerUser(String name, String email, String password){
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("tag", register_tag));
params.add(new BasicNameValuePair("name", name));
params.add(new BasicNameValuePair("email", email));
params.add(new BasicNameValuePair("password", password));
// getting JSON Object
JSONObject jObj = jsonParser.getJSONFromUrl(registerURL, params);
// return json
return jObj;
}
/**
* Function get Login status
* */
public boolean isUserLoggedIn(Context context){
Databasehandler db = new Databasehandler(context);
int count = db.getRowCount();
if(count > 0){
// user logged in
return true;
}
return false;
}
public String getAppCategorydetail(Context context){
Databasehandler db = new Databasehandler(context);
String count = db.getAppCategorydetail();
return count;
}
/**
* Function to logout user
* Reset Database
* */
public boolean logoutUser(Context context){
Databasehandler db = new Databasehandler(context);
db.resetTables();
return true;
}
public JSONObject chname(String name)
{
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("tag", name_tag));
params.add(new BasicNameValuePair("name", name));
JSONObject jObj = jsonParser.getJSONFromUrl(name1, params);
return jObj;
}
}
请为此问题提供任何正确的建议。