Spinner 的用法

package com.music.my.pk;


import java.util.ArrayList;
import java.util.List;


import com.utils.pk.MyFileTree;


import android.R.integer;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;


public class MainActivity extends Activity {
    /** Called when the activity is first created. */
private Spinner spinner;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        spinner = (Spinner)findViewById(R.id.sp);
        
        spinner.setOnItemSelectedListener(new SpLS());
        
        
        spinner.setPrompt( "本机可用歌曲名" );  //设置头部 
        MyFileTree tree = new MyFileTree();  //此类返回的是SD卡上的所有文件名
        //得到所有文件
    
        String [ ] items = tree.getFileTree(Environment.getExternalStorageDirectory().toString());
        
        ArrayAdapter array_adapter = new ArrayAdapter <String> ( this, android.R.layout.simple_spinner_item, items );
        array_adapter.setDropDownViewResource ( android.R.layout.simple_spinner_dropdown_item );  
        spinner.setAdapter ( array_adapter );    
       
        
        
        
    }
    
    
    //得到选择的spinner的值
    private class SpLS implements OnItemSelectedListener{


@Override
public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
String musicFile = MainActivity.this.spinner.getItemAtPosition(position).toString();
Toast.makeText(MainActivity.this, musicFile, 1).show();

}


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

}
   
    }

}

/////////////////////////////////////////////////////////////////////main,xml

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


    <Spinner 
        android:id="@+id/sp"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />
</LinearLayout>