¿Cómo comienzo un fragmento en mi aplicación de Android desde una notificación en la barra de notificaciones?

He intentado implementaresta respuesta de crear mi propia acción y luego establecer la acción según la intención, pero no estoy seguro de cómo usarla y qué se requiere adicionalmente, como agregar algo al manifiesto.

Tengo una clase de notificación que recibe un contexto, un mensaje y luego una acción. Luego quiero filtrar esa acción para determinar qué fragmento lanzar, pero no sé cómo lanzar un fragmento en lugar de lanzar una actividad.

Aquí está mi clase de Notifications.java (incompleta):

public class Notifications {

    private Context mContext;

    public Notifications(Context context) {
        this.mContext = context;
    }

    public static void notify(Context context, String message, String  action) {

        //Action you invent should include the application package as a prefix — for example: "com.example.project.SHOW_COLOR".
        action = "my.package.name.here.frag."+action;

        //Construct a user message.
        String appName = context.getResources().getString(R.string.app_name);

        // Use the Notification manager to send notification
        NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
        // Create a notification using android stat_notify_chat icon. 
        Notification notification = new Notification(R.drawable.ic_stat_notification, message, 0);

        //Sound, lights, vibration.
        //REMEMBER PERMISSIONS.
        notification.defaults |= Notification.DEFAULT_SOUND;
        notification.defaults |= Notification.DEFAULT_VIBRATE;
        notification.defaults |= Notification.DEFAULT_LIGHTS;

        // Create a pending intent to open the application when the notification is clicked.
        //Restart the app.
        Intent launchIntent = null;

        //Get the action and based on what the action is, launch the application displaying the appropriate fragment.
        if (action.equalsIgnoreCase("friend")){
            //New friend notification
            //Launch application displaying the list of friends


        }
        if (action.equalsIgnoreCase("article")){
            //New article has been posted
            //Launch application displaying the news feed fragment


        }
        if (action.equalsIgnoreCase("points")){
            //Points scored notification
            //Launch application displaying the user's profile


        }
        if (action.equalsIgnoreCase("redeemable")){
            //New redeemable is offered
            //Launch application displaying the list of redeemables


        }
        if (!action.equalsIgnoreCase("friend") 
                && !action.equalsIgnoreCase("article") 
                && !action.equalsIgnoreCase("points") 
                && !action.equalsIgnoreCase("redeemable")){
            //Not specific, so launch the application from scratch displaying the activity feed

            launchIntent = context.getPackageManager().getLaunchIntentForPackage(context.getPackageName());
        }



        if(action != null && launchIntent != null){         
            launchIntent.setAction(action);         
        }

        // Set the notification and register the pending intent to it
        notification.setLatestEventInfo(context, appName, message, pendingIntent);

        // Trigger the notification
        notificationManager.notify(0, notification);
    }

}