AlertController ionic 2 Uncaught TypeError：无法读取未定义的属性“创建”

Question

我在退出应用程序时尝试进行验证，但在使用 AlertController ionic 2: 时遇到错误，我按照https://ionicframework.com/docs/api/components/alert/AlertController/ 的说明进行操作

对不起，我英语不好

我的错误：

Uncaught TypeError: Cannot read property 'create' of undefined
at Object.MyApp.exit [as fn] (main.js:143575)
at Platform.runBackButtonAction (main.js:2347)
at main.js:2022
at SafeSubscriber.schedulerFn [as _next] (main.js:54953)
at SafeSubscriber.__tryOrUnsub (main.js:1388)
at SafeSubscriber.next (main.js:1337)
at Subscriber._next (main.js:1290)
at Subscriber.next (main.js:1254)
at EventEmitter.Subject.next (main.js:7763)
at EventEmitter.emit (main.js:54927)
at main.js:104021
at t.invoke (polyfills.js:3)
at Object.onInvoke (main.js:38895)
at t.invoke (polyfills.js:3)
at e.run (polyfills.js:3)

我的代码 app.component.ts：

Answer 1

试试这个代码

 exit(){
   this.alertCtrl.create({
     title :'' , 
     subTitle:'',
     buttons:['']
   }).then(alertEt =>{
    alertEt.present();
   }) 
}