ionic2.0双击返回键退出应用

import {Component} from '@angular/core';
import {Platform, ionicBootstrap} from 'ionic-angular';
import {StatusBar} from 'ionic-native';
import {TabsPage} from './pages/tabs/tabs';
import {ToastController} from 'ionic-angular';//这个是为了出现“再按一次退出”的弹出框才import的
 
@Component({
 template: ''
})
export class MyApp {
 
 private rootPage: any;
 public static backButtonPressedOnceToExit = false;
 
 constructor(private platform: Platform,public toastCtrl:ToastController) {
 this.rootPage = TabsPage;
 
 platform.ready().then(() => {
  // Okay, so the platform is ready and our plugins are available.
  // Here you can do any higher level native things you might need.
  StatusBar.styleDefault();
 });
 platform.registerBackButtonAction(function(e){
  if(MyApp.backButtonPressedOnceToExit){
  platform.exitApp();
  }else{
  MyApp.backButtonPressedOnceToExit = true;
  let toast = toastCtrl.create({
   message: '再按一次退出',
   duration: 2000,
   position: 'bottom'
  });
  toast.present();
  setTimeout(function(){
   MyApp.backButtonPressedOnceToExit = false;
  },2000)
  }
 },101)
 }
}
ionicBootstrap(MyApp);