ionic3 Injectable 引入NavController

在service里 引入 navcontroller 报错

And I get error No provider for NavController.

　　一个比较容易解决的方法，

import {IonicApp, LoadingController, ToastController, Loading, NavController, App} from 'ionic-angular';

constructor(private http: Http,
              private storageService:StorageService,
              public toastCtrl :ToastController,public loadingCtr:LoadingController,
              public appCtrl: App,
              ) {

    console.log('Hello HttpRequestService Provider');
  }

if (error.status == 500) {
            if(JSON.parse(error._body).ret_code== "98" || JSON.parse(error._body).ret_code== "99" ){
                msg = 'token失效,请重新登录!';
                let activeNav: NavController = this.appCtrl.getActiveNav();
                console.log(activeNav)
                activeNav.push("LoginPage");
            }else {
                msg = '网络连接错误';
            }
            console.error(msg+'，请检查网络是否连接');
        }

　　这是一种比较有效的替代方式，