Change visibility of ActionBar item on change tab

Question

I have Activity with 3 tabs as Fragments. I also have 3 ActionBar items. On each tab only one item should be displayed and others should be in overflow menu. My code looks like this

private void updateMenuItemsVisibility()
{
    MenuItem itemAddGate = menu.findItem(R.id.action_add_gate);
    MenuItem itemAddLinking = menu.findItem(R.id.action_new_linking);
    MenuItem itemNewConversation = menu.findItem(R.id.action_new_conversation);
    MenuItemCompat.setShowAsAction(itemNewConversation,
            MenuItemCompat.SHOW_AS_ACTION_NEVER);
    MenuItemCompat.setShowAsAction(itemAddLinking, MenuItemCompat.SHOW_AS_ACTION_NEVER);
    MenuItemCompat.setShowAsAction(itemAddGate, MenuItemCompat.SHOW_AS_ACTION_NEVER);
    if (viewPager.getCurrentItem() == 0)
    {
        MenuItemCompat.setShowAsAction(itemNewConversation,
                MenuItemCompat.SHOW_AS_ACTION_ALWAYS);
    }
    if (viewPager.getCurrentItem() == 1)
    {
        MenuItemCompat.setShowAsAction(itemAddLinking, MenuItemCompat.SHOW_AS_ACTION_ALWAYS);
    }
    if (viewPager.getCurrentItem() == 2)
    {
        MenuItemCompat.setShowAsAction(itemAddGate, MenuItemCompat.SHOW_AS_ACTION_ALWAYS);
    }
}

and it works... on Android 4.x. On 2.1 line for hiding seems not to work. When I change tab to second tab 2 items appear, on third 3 items. Switching to previous tabs does not hide items. I'm using ActionBarCompat. Is it a bug?

edit: Actually it also behaves like this on Samsung Galaxy S (first one) running CyanogenMod on Android 4.1. So it might be connected to situation when we have physical button instead of software keys.

Answer 1

I'm not quite sure but the problem may be that API < 11 do not know the SHOW_AS_ACTION_ALWAYS as the the actionbar wasn't implemented yet.

That's why you have to add 2 additional lines of code in your menus like this:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:yourapp="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/new_sms"
        android:title="@string/create_sms"
        android:orderInCategory="1"
        android:showAsAction="always"
        yourapp:showAsAction="always"
        android:icon="@drawable/arrow_right" />
</menu> 

The lines xmlns:yourapp="http://schemas.android.com/apk/res-auto" and yourapp:showAsAction="always" make it possible that the icons are always seen. Even for API 7 - 10. Else the menu items will appear in the overflow menu.

I'm not sure how to implement this programmatically but you could write 3 menu ressources like that and call onSupportInvalidateOptionsMenu() to let the fragments show their own menus. If you do so don't forget to call setHasOptionsMenu(true) in the fragments' onCreate().