Android action bar not showing overflow

If you want to show the three dots, irrespective of device menu button! then you can call this method in your application class’ onCreate method-

private void makeActionOverflowMenuShown() {
    //devices with hardware menu button (e.g. Samsung Note) don't show action overflow menu
    try {
        ViewConfiguration config = ViewConfiguration.get(this);
        Field menuKeyField = ViewConfiguration.class.getDeclaredField("sHasPermanentMenuKey");
        if (menuKeyField != null) {
            menuKeyField.setAccessible(true);
            menuKeyField.setBoolean(config, false);
        }
    } catch (Exception e) {
        Log.d(TAG, e.getLocalizedMessage());
    }
}