How to force use of overflow menu on devices with menu button

EDIT: Modified to answer for the situation of physical menu button.

This is actually prevented by design. According to the Compatibility Section of the Android Design Guide,

"...the action overflow is available from the menu hardware key. The resulting actions popup... is displayed at the bottom of the screen."

You'll note in the screenshots, phones with a physical menu button don't have an overflow menu in the ActionBar. This avoids ambiguity for the user, essentially having two buttons available to open the exact same menu.

To address the issue of consistency across devices: Ultimately it's more important to the user experience that your app behave consistently with every other app on the same device, than that it behave consistently with itself across all devices.

You can also use this little hack here:

try {
    ViewConfiguration config = ViewConfiguration.get(this);
    Field menuKeyField = ViewConfiguration.class.getDeclaredField("sHasPermanentMenuKey");
    if (menuKeyField != null) {
        menuKeyField.setAccessible(true);
        menuKeyField.setBoolean(config, false);
    }
} catch (Exception ignored) {
}

Good place to put it would be the onCreate-Method of your Application class.

It will force the App to show the overflow menu. The menu button will still work, but it will open the menu in the top right corner.

[Edit] Since it has come up several times now: This hack only works for the native ActionBar introduced in Android 3.0, not ActionBarSherlock. The latter uses its own internal logic to decide whether to show the overflow menu. If you use ABS, all platforms < 4.0 are handled by ABS and are thus subjected to its logic. The hack will still work for all devices with Android 4.0 or greater (you can safely ignore Android 3.x, since there aren't really any tablets out there with a menu button).

There exists a special ForceOverflow-Theme that will force the menu in ABS, but apperently it is going to be removed in future versions due to complications.

I use to workaround it by defining my menu like this (also with ActionBarSherlock icon used in my example):

<menu xmlns:android="http://schemas.android.com/apk/res/android" >

    <item
        android:id="@+id/menu_overflow"
        android:icon="@drawable/abs__ic_menu_moreoverflow_normal_holo_light"
        android:orderInCategory="11111"
        android:showAsAction="always">
        <menu>
            <item
                android:id="@+id/menu_overflow_item1"
                android:showAsAction="never"
                android:title="@string/overflow_item1_title"/>
            <item
                android:id="@+id/menu_overflow_item2"
                android:showAsAction="never"
                android:title="@string/overflow_item2_title"/>
        </menu>
    </item>

</menu>

I admit that this may require manual "overflow-management" in your xml, but I found this solution useful.

You can also force device to use HW button to open the overflow menu, in your activity:

private Menu mainMenu;

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // TODO: init menu here...
    // then:
    mainMenu=menu;
    return true;
}

@Override
public boolean onKeyUp(int keycode, KeyEvent e) {
    switch(keycode) {
        case KeyEvent.KEYCODE_MENU:
            if (mainMenu !=null) {
                mainMenu.performIdentifierAction(R.id.menu_overflow, 0);
            }
    }

    return super.onKeyUp(keycode, e);
}

:-)