Actions can be defined in a menu XML file that resides in the Resources/menu folder, or it can be created programmatically using API calls. We will define the New and Refresh actions in an XML file named POIListViewMenu.xml.

To create POIListViewMenu.xml, perform the following steps:

You now need to fill in the definitions for the two actions we identified. Unfortunately, Xamarin Studio does not contain a template for menu XML files, so you have to hunt the format down from Android documentation or online examples. The following code contains definitions for actionNew and actionRefresh:

<menu xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:id="@+id/actionNew"
    android:icon="@drawable/ic_new"
    android:title="New"
  android:showAsAction="ifRoom" />
  <item android:id="@+id/actionRefresh"
    android:icon="@drawable/ic_refresh"
    android:title="Refresh"
  android:showAsAction="ifRoom" />
</menu>

Note that from the menu definition, we have referenced two new drawables; ic_new and ic_refresh. We need to add these images to the project the same way that we did for the ic_app icon in Chapter 3, Creating the Points of Interest App. The images can be found in the drawable folder present in the assets location.

The OnCreateOptionsMenu() method is called to give an opportunity to the Activity parameter to define actions for the ActionBar. The Activity class provides a MenuInflater method, which reads the XML definition file and places the action defined on the ActionBar. The following code shows the implementation from the code bundle:

public override bool OnCreateOptionsMenu(IMenu menu)
{
  MenuInflater.Inflate(Resource.Menu.poiListViewMenu, menu);
  return base.OnCreateOptionsMenu(menu);
}

The OnOptionsItemSelected() method is called whenever an action in the ActionBar is clicked and an instance of IMenuItem is passed in. The IMenuItem.ItemId instance corresponds to the ID specified in the item definition and can be used to determine which action was clicked on. The following code shows the implementation of OnOptionsItemSelected() from the code bundle:

public override bool OnOptionsItemSelected (IMenuItem item)
{
  switch (item.ItemId)
  {
    case Resource.Id.actionNew: 
    // place holder for creating new poi
    return true;

    case Resource.Id.actionRefresh: 
    POIData.Service.RefreshCache ();
    _adapter.NotifyDataSetChanged ();
    return true;

    default :
    return base.OnOptionsItemSelected(item);
  }
}