ActionBar(15)自定义操作提供器ActionProvider之返回空ActionView

package com.e.acationbar;

import android.content.Context;
import android.view.ActionProvider;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.MenuItem.OnMenuItemClickListener;
import android.view.SubMenu;
import android.view.View;
import android.widget.Toast;

public class CustomActionProviderNoActionView extends ActionProvider implements OnMenuItemClickListener {
    private Context mContext;

    // 在选中悬浮菜单中的菜单时，菜单项默认执行的操作。
    @Override
    public boolean onPerformDefaultAction() {
        // TODO Auto-generated method stub
        return super.onPerformDefaultAction();
    }

    /**
     * 创建子菜单
     * 
     * @param subMenu
     */
    @Override
    public void onPrepareSubMenu(SubMenu subMenu) {
        // TODO Auto-generated method stub
        subMenu.clear();
        MenuInflater mif = new MenuInflater(mContext);
        mif.inflate(R.menu.provider_no_av, subMenu);// 通过菜单资源文件生成菜单

        // 用代码添加子菜单
        MenuItem mi = subMenu.add("用代码添加的菜单项");
        mi.setIcon(R.drawable.actionbar_camera_icon);
        mi.setOnMenuItemClickListener(this);
    }

    /**
     * @return 返回true代表有子菜单
     */
    @Override
    public boolean hasSubMenu() {
        // TODO Auto-generated method stub
        return true;
    }

    @Override
    public boolean onMenuItemClick(MenuItem item) {
        // TODO Auto-generated method stub
        int id = item.getItemId();
        Toast.makeText(mContext, "submenu " + id + "was clicked",
                Toast.LENGTH_SHORT).show();
        return true;
    }

    @Override
    public View onCreateActionView() {
        // TODO Auto-generated method stub
        return null;
    }

    public CustomActionProviderNoActionView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        mContext = context;
    }

}

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >

    <item
        android:id="@+id/action_share"
        android:actionProviderClass="android.widget.ShareActionProvider"
        android:icon="@drawable/actionbar_facefriend_icon"
        android:showAsAction="never"
        android:title="@string/share">
    </item>
    <item
        android:id="@+id/action_custom_item"
        android:actionLayout="@layout/action_view_for_main"
        android:icon="@drawable/actionbar_particular_icon"
        android:showAsAction="ifRoom|collapseActionView"
        android:title="@string/action_custom_item">
    </item>

</menu>

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="com.e.acationbar.MainActivity" >

    <item
        android:id="@+id/action_customProvider_no_actionView"
        android:actionProviderClass="com.e.acationbar.CustomActionProviderNoActionView"
        android:icon="@drawable/actionbar_setting_icon"
        android:showAsAction="always"
        android:title="@string/custom_provider_no_av">
    </item>
...
</menu>