Android UI control series: Spinner (drop-down list)

package org.hualang.Spinner;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;

public class SpinnerTest extends Activity {
    /** Called when the activity is first created. */
        private static final String[] citys={"杭州","北京","成都","大连","深圳","南京"};
        private TextView text;
        private Spinner spinner;
        private ArrayAdapter<String> adapter;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        text=(TextView)findViewById(R.id.text);
        spinner=(Spinner)findViewById(R.id.spinner);

        //将可选内容与ArrayAdapter连接
        adapter=new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,citys);
        //设置下拉列表风格
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        //将adapter添加到spinner中
        spinner.setAdapter(adapter);
        //添加Spinner事件监听
        spinner.setOnItemSelectedListener(new Spinner.OnItemSelectedListener()
        {

                        @Override
                        public void onItemSelected(AdapterView<?> arg0, View arg1,
                                        int arg2, long arg3) {
                                // TODO Auto-generated method stub
                                text.setText("你所在的城市是："+citys[arg2]);
                                //设置显示当前选择的项
                                arg0.setVisibility(View.VISIBLE);
                        }

                        @Override
                        public void onNothingSelected(AdapterView<?> arg0) {
                                // TODO Auto-generated method stub

                        }

        });
    }
}

<?xml version="1.0" encoding="utf-8"?>  
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:orientation="vertical"  
    android:layout_width="fill_parent"  
    android:layout_height="fill_parent"  
    >  
<TextView  
        android:id="@+id/text"  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:text="您所在的城市"  
    />  
<Spinner  
        android:id="@+id/spinner"  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_centerHorizontal="true"  
/>  
</LinearLayout>