j2me一个传值问题，大家快来啊，散分啦！

其实我想要这样的效果，在Sysconfig()里，传递textfield的值到config()里的domain里。具体如何操作呢？
if (domainName != "")
    {
     config.domain = domainName;
    }
传递domainName;的值到config()里的domain里。
Sysconfig.javapackage M2M.midlet;import javax.microedition.lcdui.ChoiceGroup;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.TextField;import M2M.Config;public class Sysconfig extends Form implements CommandListener 
{
private Command enterCmd = null;
private Command canselCmd = null;
private ChoiceGroup cb=null;
private Display dis;
private Form form;
private Config config=null;
private TextField tf;
public String domainName;
public Sysconfig(Display dis,Form form)
{
super("系统配置");
this.dis=dis;
this.form=form;
canselCmd = new Command("返回主菜单",Command.BACK,1);
enterCmd = new Command("保存配置",Command.OK,1);
String [] choices=new String[1];
choices[0]="是";
cb=new ChoiceGroup("使用CMWAP代理",ChoiceGroup.MULTIPLE,choices,null);
config=new Config();
if (config.needproxy==true) cb.setSelectedIndex(0, true);
tf=new TextField("域名地址",config.domain,25,TextField.ANY);
this.append(cb);
this.append(tf);
this.addCommand(enterCmd);
this.addCommand(canselCmd);
this.setCommandListener(this);
}
public void commandAction(Command c, Displayable d)
{
if (c == this.enterCmd)
{ boolean[] sa_return = new boolean[1];
cb.getSelectedFlags(sa_return) ;
if (sa_return[0]==true)
config.needproxy=true;
else
config.needproxy=false;
    domainName = tf.getString();
    if (domainName != "")
    {
     config.domain = domainName;
    }
    try
{
config.savedomain(domainName);
}
catch(Exception ex)
{
System.out.println("MSG@:" + ex);
}
try
{
config.saveconfig();
}
catch (Exception ex)
{
System.out.println("Msg:" + ex);
}

}
else if (c == this.canselCmd)
{
dis.setCurrent(form);
}
}
}config.javapackage M2M;import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;import javax.microedition.io.Connector;
import javax.microedition.io.file.FileConnection;
import javax.microedition.io.file.FileSystemRegistry;
import javax.microedition.lcdui.ChoiceGroup;
import javax.microedition.lcdui.List;
import javax.microedition.lcdui.TextBox;
import javax.microedition.lcdui.TextField;
import javax.microedition.rms.InvalidRecordIDException;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms.RecordStoreException;
import javax.microedition.rms.RecordStoreFullException;
import javax.microedition.rms.RecordStoreNotOpenException;public class Config implements Runnable
{
public String domain;
public String host= domain + "/java";
//public String host="http://localhost/chengyu/java/";
public String LoginUrl=host+"/index.php?op=login";
public String DownUrl=host+"/index.php?op=down";
public String UploadUrl=host+"/index.php?op=upload";
public String DownImgUrl = domain + "/wap/imgs/";

public String root="file:///root1/";

public String exam_file="exam.xml";
public String answerfile="chengyu_answer.xml";
public static boolean debug=true;
public boolean needproxy=false;
public static String proxy="http://10.0.0.172/";
public String username="";
public String password="";
public Config()
{
String platform = System.getProperty("microedition.platform");
if(platform.startsWith("SonyEricsson"))
{
this.root="file:///e:/";
}
else if(platform.startsWith("Nokia"))
{
this.root="file:///e:/";
}
else if(platform.startsWith("j2me")) 
{
this.root="file:///root1/";
}
else
{
this.root="file:///root1/";

}
try
{
loadconfig();
}
catch (Exception ex)
{
System.out.println("Message:" + ex);
}

}