[Android] How to add a Dropdown item on the action bar

Action Bar是android 3.0提供的一個功能,像下圖這樣
(The Action Bar  APIs were first added in Android 3.0 as following picture)




這個範例將教大家,如何在Action bar上加入下拉選單
(This example will teach you how to add a dropdown item on action bar)


File : MainActivity.java

import java.util.ArrayList;
import android.os.Bundle;
import android.app.ActionBar;
import android.app.Activity;
import android.app.ActionBar.OnNavigationListener;
import android.util.Log;
import android.widget.ArrayAdapter;

public class MainActivity extends Activity {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  final ActionBar actionBar = getActionBar();
  actionBar.setDisplayShowTitleEnabled(false);
  actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);

  ArrayList itemList = new ArrayList();
  itemList.add("WMP");
  itemList.add("iTunes");
  itemList.add("Winamp");

  ArrayAdapter adapt = new ArrayAdapter(this,
    android.R.layout.simple_list_item_1, android.R.id.text1,
    itemList);
  actionBar.setListNavigationCallbacks(adapt, new DropDownListenser());
 }

 class DropDownListenser implements OnNavigationListener {

  public boolean onNavigationItemSelected(int itemPosition, long itemId) {
   if (itemPosition == 0) // windows media player
   {
    Log.e("log", "you choose WMP");
   }

   if (itemPosition == 1) // iTunes
   {
    Log.e("log", "you choose iTunes");
   }
   if (itemPosition == 2) // Winamp
   {
    Log.e("log", "you choose Winamp");
   }

   return true;

  }
 }

}