“显示”；空"；当值来自另一类java android时

我从服务器获取数据，当我使用另一个类中的服务器的值时，它显示null而不是实际值来自服务器…我有两个类activity2.java和notepadv3.java数据来自activity2.java中的服务器，当我使用该数据时，它显示null…我将粘贴这两个类…请解决我的问题为什么显示空的问题

package cabs.h;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;

import android.app.ListActivity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.os.Bundle;
import android.util.Log;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ContextMenu.ContextMenuInfo;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.AdapterView.AdapterContextMenuInfo;
public class Notepadv3 extends ListActivity {
private static final int ACTIVITY_CREATE=0;
private static final int ACTIVITY_EDIT=1;
private static final int INSERT_ID = Menu.FIRST;
private static final int DELETE_ID = Menu.FIRST + 1;
private NotesDbAdapter mDbHelper;
private Long mRowId;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.listonruntime);
    mDbHelper = new NotesDbAdapter(this);
    mDbHelper.open();
    fillData();
    registerForContextMenu(getListView());

}
private void fillData() {
    Cursor notesCursor = mDbHelper.fetchAllNotes();
    startManagingCursor(notesCursor);
     String s=NotesDbAdapter.KEY_TITLE;
    Log.i("saurabh trivedi log cat,,,,,,,,,",s);
    final String PREFS_NAME1 = "PrefSettings";

    // Create an array to specify the fields we want to display in the list (only TITLE)
    String[] from = new String[]{NotesDbAdapter.KEY_BODY,NotesDbAdapter.KEY_TITLE};
  // String[] too = new String[]{NotesDbAdapter.KEY_TITLE};
    // and an array of the fields we want to bind those fields to (in this case just text1)
    int[] to = new int[]{R.id.toptext,R.id.middletext};

   SimpleCursorAdapter notes =   
                                new SimpleCursorAdapter(this, R.layout.row, notesCursor, from, to);

setListAdapter(notes);

}




@Override
public void onCreateContextMenu(ContextMenu menu, View v,
        ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu, v, menuInfo);
    menu.add(0, DELETE_ID, 0, R.string.menu_delete);
}

@Override
public boolean onContextItemSelected(MenuItem item) {
    switch(item.getItemId()) {
        case DELETE_ID:
            AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
            mDbHelper.deleteNote(info.id);
            fillData();
            return true;
    }
    return super.onContextItemSelected(item);
}

  @Override
protected void onSaveInstanceState(Bundle outState) 
{
    super.onSaveInstanceState(outState);
    saveState();
    outState.putSerializable(NotesDbAdapter.KEY_ROWID, mRowId);
}

@Override
protected void onPause() {
    super.onPause();
    saveState();
}

@Override
protected void onResume() {
    super.onResume();

}

**

和Activity2.java类代码为

package cabs.h;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
public class Activity2 extends Activity {
public  static String resp1;
   @Override
    public  void onCreate(Bundle savedInstanceState)
   {
        super.onCreate(savedInstanceState);


                     try {

                      String tURL="http://qrrency.com/mobile/j2me/cab/CabRequestStatus.php?requestid=130";
                      URL url = new URL("http://qrrency.com/mobile/j2me/cab/CabRequestStatus.php?requestid=130");
                      Log.i("Line----saurabh trivedi-----", tURL);
                        BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
                        int m=0;
                        StringBuffer buffer=new StringBuffer();
                    String str1 = " ";
                        while ((m=in.read())!=-1) 
                        {
                                   **buffer.append((char)m);
                                    str1=str1+(char)m;
                                 cabbookingapplication.resp =str1;
                                 resp1=cabbookingapplication.resp;
                           Log.i("Line----saurabh trivedi---,,,--",resp1);**

                        }



                       in.close();



                        } catch (MalformedURLException e)
                        {
                        } catch (IOException e) 
                        {

                    }
                         Log.i("Line----saurabh trivedi---,,,--",resp1);                
   }

   }      

---

我认为如果不需要UI，就不应该从Activity扩展Activity2.java。如果您像在Notepadv3.java中那样使用“new”关键字实例化Activity2.java，则不会执行Activity2的onCreate方法。onCreate不是构造函数。这就是静态变量“resp1”为空的原因，因为它从未设置过

从Activity2中删除“扩展活动”，并将代码从onCreate移到返回数据的静态函数中，您可以在Notepadv3.java中调用该函数

class Activity2 {
  public static String getData() {
    String data;
    // you code for retrieving data
    return data;
  }
}

在Notepadv3类调用中

String sss = Activity2.getData();

获取您的数据。活动是Android的一个UI类，可以从中扩展。决不能用“new”关键字实例化它的子类。系统正在为您创建一个实例，如果您启动了一个意图，那么系统将在活动的生命周期中调用onCreate

String sss = Activity2.getData();