ListView的addHeaderView

public class MainActivity extends Activity {
ListView lv;
LinearLayout rl;
TextView tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LayoutInflater inflater = LayoutInflater.from(this);
rl = (LinearLayout) inflater.inflate(
R.layout.item_header_search_two, null);
tv = (TextView) rl.findViewById(R.id.tv_search);
lv=(ListView) findViewById(R.id.listView1);
lv.addHeaderView(rl);
String [] a={"1","2"};
 ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
   android.R.layout.simple_list_item_single_choice, a);
 lv.setAdapter(adapter);

}

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#f0f0f0"
    android:orientation="vertical" >


    <RelativeLayout
        android:id="@+id/rl_search"
        android:layout_width="fill_parent"
        android:layout_height="40dp"
        android:layout_gravity="center_horizontal"
        android:layout_marginBottom="5dp"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:layout_marginTop="5dp"
        
        android:gravity="center" >


        <EditText
            android:id="@+id/tv_search"
            android:layout_width="wrap_content"
            android:layout_height="40dp"
            android:layout_gravity="center_horizontal"
            android:layout_marginLeft="10dp"
            android:layout_marginRight="10dp"
           
            android:drawablePadding="5dp"
            android:gravity="center_vertical"
            android:hint="搜索"
            android:textColor="#bcbcbc"
            android:textSize="16sp" 
            android:background="@null"
            />
    </RelativeLayout>


</LinearLayout>