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我使用ionic2在新的应用程序，我想路由调用来自服务器的HTTP请求承诺函数内我的网页，导航离子2
一个承诺函数里面我要访问的Navcontroller在promise函数内部，但Navcontroller不能从promise函数内部访问。 承诺的功能是的AuthenticationService
内部功能的承诺，这是我的里面app.component.ts代码：
import {Component, ViewChild, Inject} from '@angular/core';
import {Platform, NavController} from 'ionic-angular';
import { StatusBar } from 'ionic-native';
import { HomePage } from '../pages/home/home';
import { LoginPage } from '../pages/login/login';
import {Authentication} from '../providers/authentication';
@Component({
template: `<ion-nav #myNav [root]="rootPage"></ion-nav>`,
providers:[Authentication],
})
export class MyApp {
@ViewChild('myNav') public nav : NavController
//rootPage = LoginPage;
constructor(platform: Platform, private auth:Authentication) {
platform.ready().then(() => {
StatusBar.styleDefault();
});
}
ngOnInit() {
this.auth.index()
.then(function (data) {
if(data['flag']==1)
{
this.nav.setRoot(HomePage);
}
else
{
this.nav.setRoot(LoginPage);
}
})
，这是错误：
EXCEPTION: Uncaught (in promise): TypeError: Cannot read property 'nav' of null
TypeError: Cannot read property 'nav' of null.