android解析json报空指针异常。

[印第安囚徒]

代码如下

package com.student.activity;

import java.net.URI;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.json.JSONArray;
import org.json.JSONObject;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;

public class StuManagerActivity extends Activity {
	private static final String TAG = "StuManagerActivity";
	private List<HashMap<String, Object>> list = null;
	private HashMap<String, Object> stu = null;

	private ListView listView = null;
	private static String url = "http://192.168.1.103:8080/StudentServer/getJsonStu.action";

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		listView = (ListView) findViewById(R.id.stuList);
		
		getServerData(url);
	}

	public void getServerData(String url) {
		// 提供默认的HttpClient实现
		HttpClient client = new DefaultHttpClient();
		HttpPost request;

		try {
			request = new HttpPost(new URI(url));
			HttpResponse response = client.execute(request);
			// 判断请求是否成功
			if (response.getStatusLine().getStatusCode() == 200) {
				HttpEntity entity = response.getEntity();
				if (entity != null) {
					String out = EntityUtils.toString(entity, "UTF-8");
					Log.i(TAG, out);
					JSONArray jsonArray = new JSONArray(out);
					System.out.println(jsonArray.length());
					list = new ArrayList<HashMap<String, Object>>();
					System.out.println(list.size());
					
					for (int i = 0; i < jsonArray.length(); i++) {
						JSONObject jsonObject = (JSONObject) jsonArray.get(i);
						String stuName = jsonObject.getString("studentName");
						String stuSex = jsonObject.getString("stuSex");
						String phone = jsonObject.getString("phone");
						
						stu.put("stuName", stuName);
						stu.put("stuSex", stuSex);
						stu.put("phone", phone);
						
						System.out.println(stuName);
						
						list.add(stu);
						System.out.println(list.size()+"");
					}
					SimpleAdapter adapter = new SimpleAdapter(
							StuManagerActivity.this, list, R.layout.item,
							new String[] { "stuName", "stuSex", "phone" },
							new int[] { R.id.stuName, R.id.stuSex, R.id.phone });
					
					listView.setAdapter(adapter);
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
			Log.e(TAG, e.toString());
			Toast.makeText(StuManagerActivity.this, "获取数据失败！", Toast.LENGTH_LONG).show();
		}

	}
}

[印第安囚徒]

System.out.println(list.size());这里还能正常显示，到了System.out.println(stuName);这里就不能正常显示了，从服务器获取到json代码成功，能显示出来。

[印第安囚徒]

还有一个就是json在网页上显示是乱码。

但是查看源代码又能正常显示

android上面也能显示


服务端代码：

package com.server.action;

import java.io.IOException;
import java.util.List;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;
import com.server.dao.IStuInfoDao;
import com.server.model.StudentInfo;
import com.server.util.DateTimeUtil;

public class StuInfoAction extends ActionSupport{
	private static final long serialVersionUID = -989477296829078690L;

	private IStuInfoDao IStuDao;

	public IStuInfoDao getIStuDao() {
		return IStuDao;
	}

	public void setIStuDao(IStuInfoDao iStuDao) {
		IStuDao = iStuDao;
	}
	
	public void getJson(){
		List<StudentInfo> list = IStuDao.queryAllStudent();
		JSONArray jsonArray = new JSONArray();
		int i=0;
		for (StudentInfo si : list) {
			JSONObject jsonObject = new JSONObject();
			jsonObject.put("remark",si.getRemark());
			jsonObject.put("email", si.getEmail());
			jsonObject.put("BirthDay", DateTimeUtil.TimestampToString(si.getBirthDay()));
			jsonObject.put("cardId", si.getCardId());
			jsonObject.put("phone", si.getPhone());
			jsonObject.put("stuSex", si.getStuSex());
			jsonObject.put("studentName", si.getStudentName());
			jsonObject.put("className", si.getClassInfo().getClassName());
			jsonObject.put("sid", si.getSid());
			
			jsonArray.add(i,jsonObject);
			i++;
		}
		try {
			ServletActionContext.getResponse().setCharacterEncoding("UTF-8");
			ServletActionContext.getResponse().getWriter().write(jsonArray.toString());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	
}

[印第安囚徒]

服务端用的是SSH三大框架做的。struts配置

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>
	<package name="p1" extends="json-default" namespace="/">
		
		<action name="*Class" class="ClassInfoAction" method="{1}">
			<result type="json"></result>
		</action>
		
		<action name="*Stu" class="StuInfoAction" method="{1}">
			<result type="json"></result>
		</action>

		<action name="*User" class="UserInfoAction" method="{1}">
			<result type="json"></result>
		</action>
	
	</package>
</struts>    

[印第安囚徒]

[Quote=引用 5 楼 的回复:]
我怎么没看到你的stu对象是在哪里new的？乱码是编码问题。

引用楼主 的回复:
代码如下
Java code

package com.student.activity;

import java.net.URI;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

……
[/Quote]

我都改的UTF-8的编码诶。

[qdkfriend]

首先 我觉得你客户端不该把UI线程和网络线程混在一起，希望能写成异步的
另外 你的json在网页显示是乱码，无非是编码的问题

[Anbrul]

我怎么没看到你的stu对象是在哪里new的？乱码是编码问题。[Quote=引用楼主 的回复:]
代码如下
Java code

package com.student.activity;

import java.net.URI;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache……
[/Quote]