ionic监听android返回键实现“再按一次退出”功能

angular.module("app").run(["$rootScope", "$ionicPlatform",
 "$location", "$ionicHistory",
 function ($rootScope, $ionicPlatform, $location, $ionicHistory) {
  "use strict";
  
  // 当用户在主页面， 按返回键时，给予提示，如果在2s内再次出发返回键，就退出app
  function showTipMsg() {
   window.plugins.toast.showShortCenter("在按一次退出app"); // toast是cordova的一个插件cordova-plugin-x-toast，也可以用ionic的弹窗来代替
   $rootScope.exitApp = true;
   const delay = 2000;
   setTimeout(() =  {
    $rootScope.exitApp = false;
   }, delay);
  }
  
  // 判断当前路由，是否是project， mission，mine， message这几个主页面
  function isExitPage() {
   let path = $location.path(),
    state = _.last(path.split("/")),
    ary = ["project", "mission", "mine", "", "message"];
   return _.includes(ary, state);
  }
  
  // 注册返回事件
  function registerBackButton(event) {
   event.preventDefault();
   $cordovaKeyboard.isVisible() && $cordovaKeyboard.close();
   if (isExitPage()) {
    $rootScope.exitApp && ionic.Platform.exitApp();
    !$rootScope.exitApp && showTipMsg();
   } else {
    $ionicHistory.goBack();
   }
   return false;
  }
  
  // ionic 环境已经准备完毕
  ionic.Platform.ready(() =  {
   try {
    const priority = 101;
    $ionicPlatform.is("Android") && $ionicPlatform.registerBackButtonAction(registerBackButton, priority);
   } catch (e) {
    console.warn("Application is running in browser causes inspection failed.");
   }
  });
 }]);