我有一个android应用程序，需要使用php连接android和mysql数据库，该应用程序运行良好。只有显示用户动作不起作用。这种方法将用户显示在带有一些数据的列表中。

有人能帮我纠正这个错误吗？？

LogCat错误

       04-14 21:37:37.378: E/AndroidRuntime(1854): Caused by: java.lang.NullPointerException
04-14 21:37:37.378: E/AndroidRuntime(1854):     at com.devleb.loginDemo.UserListActivity$getUserList.doInBackground(UserListActivity.java:143)
04-14 21:37:37.378: E/AndroidRuntime(1854):     at com.devleb.loginDemo.UserListActivity$getUserList.doInBackground(UserListActivity.java:1)
04-14 21:37:37.378: E/AndroidRuntime(1854):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
04-14 21:37:37.378: E/AndroidRuntime(1854):     at java.util.concurrent.FutureTask.run(FutureTask.java:234)
04-14 21:37:37.378: E/AndroidRuntime(1854):     ... 4 more

用户.java

package com.devleb.loginDemo;
import java.util.HashMap;
//@SuppressWarnings("serial")
public class User extends HashMap<String, String> {
    /**
     * 
     */
    String name;
    String date;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getDate() {
        return date;
    }
    public void setDate(String date) {
        this.date = date;
    }
}

自定义适配器.java

package com.devleb.loginDemo;
import java.util.ArrayList;
import java.util.Date;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
public class CustomAdapter extends BaseAdapter {
    private static ArrayList<User> usersList;
    // private static ArrayList name, date;
    LayoutInflater layoutInflater;
    String[] userName;
    Date[] createdDate;
    Context context;
    @SuppressWarnings("rawtypes")
    public CustomAdapter(ArrayList<User> result, Context c) {
        usersList = result;
        context = c;
    }
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return usersList.size();
    }
    @Override
    public Object getItem(int arg0) {
        // TODO Auto-generated method stub
        return usersList.get(arg0);
    }
    @Override
    public long getItemId(int arg0) {
        // TODO Auto-generated method stub
        return arg0;
    }
    @Override
    public View getView(int position, View arg1, ViewGroup parent) {
        // TODO Auto-generated method stub
        layoutInflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View row = null;
        row = layoutInflater.inflate(R.layout.list_item, parent, false);
        TextView txtCreateDate = (TextView) row
                .findViewById(R.id.txtCreateDate);
        txtCreateDate.setText(usersList.get(position).getDate().toString());
        TextView txtName = (TextView) row.findViewById(R.id.name);
        txtName.setText(usersList.get(position).getName());
        return row;
    }
}

用户列表活动.java

package com.devleb.loginDemo;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Intent;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
public class UserListActivity extends ListActivity {
    JSONParser jsonParser = new JSONParser();
    // ArrayList<HashMap<String, String>> usersList;
    // **** added from internt*************///
    @SuppressWarnings("rawtypes")
    ArrayList<User> arrayList_userList;
    ListView lvUsers;
    // **** added from internt*************///
    private static String url_display_user = "http://10.0.3.2/android_connect/display_user.php";
    // JSON Node names
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_MESSAGE = "message";
    private static final String TAG_ID = "id";
    private static final String TAG_USERS = "userlist";
    private static final String TAG_USER = "user";
    private static final String TAG_DATE = "date";
    // private static final String TAG_NAME = "name";
    // employees JSONArray
    JSONArray users = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_user_list);
        // usersList = new ArrayList<HashMap<String, String>>();
        new getUserList().execute();
        // getListView
        lvUsers = (ListView) findViewById(android.R.id.list);
        lvUsers.setOnItemClickListener(new OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> arg0, View view, int arg2,
                    long arg3) {
                // String id = ((TextView)
                // view.findViewById(R.id.uid)).getText()
                // .toString();
                // Intent in = new Intent(getBaseContext(), StatusList.class);
                // in.putExtra(TAG_ID, uid);
                // startActivity(in);
            }
        });
    }
    class getUserList extends AsyncTask<String, String, String> {
        /**
         * Before starting background thread Show Progress Dialog
         * */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            UserListActivity.this.setProgressBarIndeterminateVisibility(true);
        }
        @Override
        protected String doInBackground(String... params) {
            // TODO Auto-generated method stub
            // Building Parameters
            List<NameValuePair> parametres = new ArrayList<NameValuePair>();
            // getting JSON string from URL
            JSONObject json = jsonParser.makeHttpRequest(url_display_user,
                    "GET", parametres);
            // Check your log cat for JSON reponse
            Log.d("All Users: ", json.toString());
            try {
                // Checking for SUCCESS TAG
                int success = json.getInt(TAG_SUCCESS);
                if (success == 1) {
                    // products found
                    // Getting Array of Products
                    users = json.getJSONArray(TAG_USERS);
                    // looping through All Users
                    for (int i = 0; i < users.length(); i++) {
                        JSONObject c = users.getJSONObject(i);
                        // Storing each json item in variable
                        String id = c.getString(TAG_ID);
                        String user = c.getString(TAG_USER);
                        String cdate = c.getString(TAG_DATE).toString();
                        // creating new HashMap
                        User map = new User();
                        // adding each child node to HashMap key => value
                        map.put(TAG_ID, id);
                        map.put(TAG_USER, user);
                        map.put(TAG_DATE, cdate);
                        // adding HashList to ArrayList
                        // usersList.add(map);
                        arrayList_userList.add(map);
                    }
                    // ***********************************//
                    // From the internet
                    // arrayList_userList = new
                    // ArrayList<User>(usersList.value())
                    // **********************************//
                    return json.getString(TAG_MESSAGE);
                } else {
                    return json.getString(TAG_MESSAGE);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return null;
        }
        /**
         * After completing background task Dismiss the progress dialog
         * **/
        protected void onPostExecute(String result) {
            // dismiss the dialog after getting all products
            if (result != null) {
                UserListActivity.this
                        .setProgressBarIndeterminateVisibility(false);
                /**
                 * Updating parsed JSON data into ListView
                 * */
                /*
                 * ListAdapter adapter = new
                 * SimpleAdapter(UserListActivity.this, usersList,
                 * R.layout.list_item, new String[] { TAG_ID, TAG_USER }, new
                 * int[] { R.id.uid, R.id.name }); // updating listview
                 * setListAdapter(adapter);
                 */
                lvUsers.setAdapter(new CustomAdapter(arrayList_userList,
                        getBaseContext()));
                Toast.makeText(getBaseContext(), result, Toast.LENGTH_LONG)
                        .show();
            }
        }
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.user_list, menu);
        return true;
    }
}