listview中的radiobutton如何实现单选并在avtivity中取到他的值

public class QW_HomePage_listAdapter extends BaseAdapter{
Context context;
List<HashMap<String,Object>> datas;
public static HashMap<String,Boolean> isSelected = new HashMap<String, Boolean>();
private LayoutInflater inflater = null;
boolean res;
static int isFirst =0;

public QW_HomePage_listAdapter(Context context,List<HashMap<String,Object>> datas) {
//System.out.println("---in adapter----");
this.context = context;
this.datas = datas;
inflater = LayoutInflater.from(context);
for(int i = 0;i<datas.size();i++)
{
//System.out.println("states:"+(Boolean)datas.get(i).get("state"));
isSelected.put(String.valueOf(i), (Boolean)datas.get(i).get("state"));
}
}
@Override
public int getCount() {
return datas.size();
}

@Override
public Object getItem(int position) {
return datas.get(position);
}

@Override
public long getItemId(int position) {
return position;
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if(convertView == null){
//System.out.println("position == :"+position);
holder = new ViewHolder();
//获得layout
convertView = inflater.inflate(R.layout.qw_homepage_item, null);
holder.rb = (RadioButton) convertView.findViewById(R.id.qw_homepage_rb);

//为view设置标签
convertView.setTag(holder);
}else{
holder = (ViewHolder)convertView.getTag();
}
//System.out.println("(String)datas.get(position).get('textview')"+(String)datas.get(position).get("textview"));
holder.rb.setText((String)datas.get(position).get("text"));

//System.out.println("---states---"+(Boolean)datas.get(position).get("state"));
holder.rb.setChecked((Boolean)datas.get(position).get("state"));

//点击事件
holder.rb.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View paramView) {
//System.out.println("选中的是第"+position+"条记录");
//重置，确保最多只有一项被选中
for(String key:isSelected.keySet()){
//System.out.println("key:"+key);
isSelected.put(key,false);
}
isSelected.put(String.valueOf(position),true);
QW_HomePage_listAdapter.this.notifyDataSetChanged();

}
});

boolean res=false;
if(isSelected.get(String.valueOf(position)) == null || isSelected.get(String.valueOf(position))== false){
//System.out.println("ont  if");
res=false;
isSelected.put(String.valueOf(position), false);
}
else{
res=true;
}
holder.rb.setChecked(res);

return convertView;

}

boolean states[]={false,true,false,false};
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.qw_default_homepage);

listview = (ListView)findViewById(R.id.qw_homepage_listview);
layout = (LinearLayout)findViewById(R.id.qw_default_homepage);
myGestureDetector = new GestureDetector(this);
layout.setOnTouchListener(this);
layout.setLongClickable(true);

//设置title并获取控件
back_btn = (Button)findViewById(R.id.qw_title_left_back);
back_btn.setBackgroundResource(R.drawable.qw_left_back);
back_btn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View paramView) {
// TODO Auto-generated method stub
QW_DefaultHomePageActivity.this.finish();
}
});
save_btn = (Button)findViewById(R.id.qw_title_right_button);
save_btn.setVisibility(0);
save_btn.setBackgroundResource(R.drawable.qw_right_save);
title_top_tv = (TextView)findViewById(R.id.title_center_title);
title_top_tv.setText("默认首页设置");

String temps[]={"咨询","通信录","通知","办公"};
//boolean states[]={false,true,false,false};
for(int i = 0;i<temps.length;i++){
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("text",temps[i]);
map.put("state",states[i]);
datas.add(map);
}
adapter = new QW_HomePage_listAdapter(QW_DefaultHomePageActivity.this, datas);
listview.setAdapter(adapter);
save_btn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
saveFile();
Toast.makeText(QW_DefaultHomePageActivity.this, "保存成功", Toast.LENGTH_SHORT).show();
}
});

}//end oncreat

private HashMap<String, Boolean> state;
//保存更改后的信息
public void saveFile(){

state=adapter.isSelected;

for(int j=0;j<adapter.getCount();j++){
System.out.println("state.get("+j+")=="+state.get(String.valueOf(j)));
if(state.get(String.valueOf(j))!=null && state.get(String.valueOf(j))== true ){
@SuppressWarnings("unchecked")
HashMap<String, Object> map=(HashMap<String, Object>) adapter.getItem(j);
String username=map.get("text").toString();

//取到更改后的RadioButton的值
System.out.println("--username---"+username);

}
}
Toast.makeText(QW_DefaultHomePageActivity.this, "保存成功", Toast.LENGTH_SHORT).show();
QW_DefaultHomePageActivity.this.finish();
}

public class ViewHolder {
public CheckBox  cb;
public TextView  tv;
public ImageView iv;
public RadioButton rb;
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/qw_default_homepage"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#ffffff"
android:orientation="vertical" >

<include layout="@layout/qw_setting_title_top" />
<RelativeLayout
android:id="@+id/RelativeLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<ListView
android:id="@+id/qw_homepage_listview"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</ListView>
</RelativeLayout>
</LinearLayout>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#ffffff"
android:orientation="horizontal" >

<RadioButton
android:id="@+id/qw_homepage_rb"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#000000"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:focusable="false"
android:text="RadioButton" />

</LinearLayout>