Android ActionBar下拉选项

package com.example.actionBarTest.actionBarList;

import android.app.ActionBar;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.SpinnerAdapter;
import com.example.actionBarTest.R;

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

/**
* Created by Heyiyong on 2014-5-2 上午9:50.
*/
public class ListNavigationActivity extends Activity implements ActionBar.OnNavigationListener {
private List<Fragment> fragments;
private String[] navs = {"添加", "删除", "编辑", "查询", "更多"};
private SpinnerAdapter spinnerAdapter;

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tab_main);

spinnerAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, navs);

HomeFragment homeFragment = new HomeFragment();
MusicFragment musicFragment = new MusicFragment();
VideoFragment videoFragment = new VideoFragment();
fragments = new ArrayList<Fragment>();
fragments.add(homeFragment);
fragments.add(musicFragment);
fragments.add(homeFragment);
fragments.add(videoFragment);
fragments.add(homeFragment);

ActionBar actionBar = getActionBar();
if (actionBar != null) {
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);
actionBar.setListNavigationCallbacks(spinnerAdapter, this);
}
}

@Override
public boolean onNavigationItemSelected(int itemPosition, long itemId) {
System.out.println("itemPosition = " + itemPosition);
getFragmentManager().beginTransaction().replace(R.id.tab_main, fragments.get(itemPosition)).commit();
return true;
}

}

actionBar.setListNavigationCallbacks(spinnerAdapter, this);
这个ArrayAdapter是继承于BaseAdapter的，而BaseAdapter又实现了SpinnerAdapter接口.