当我收到朋友列表时，Facebook Graph API返回错误

Question

当我试图从Facebook获取好友列表时，我从facebook Graph API收到错误。

{"error":{"type":"OAuthException","message":"An unexpected error has occurred. Please retry your request later.","code":2}}

这是我添加的权限。

OpenRequest op = new Session.OpenRequest((Activity) HomeScreen.this);
List<String> permissions = new ArrayList<String>();
            permissions.add("email");
            op.setPermissions(permissions);
            Session session = new Session.Builder(HomeScreen.this)
                    .setApplicationId(getResources().getString(R.string.app_id))
                    .build();
            Session.setActiveSession(session);
            session.openForRead(op);