How open file in device navigation

how can i navigate trhoug file in my device and open it in ionic app? I follow this 2 tutorial both work but in the first one i can’t open file and i don’t know how to insert the second one to open file. Please help
FIRST,


SECOND.

My code

var app=angular.module(‘starter’, [‘ionic’,‘ngCordova’])
.run(function($ionicPlatform) {
$ionicPlatform.ready(function() {
if(window.cordova && window.cordova.plugins.Keyboard) {
// Hide the accessory bar by default (remove this to show the accessory bar above the keyboard
// for form inputs)
cordova.plugins.Keyboard.hideKeyboardAccessoryBar(true);

      // Don't remove this line unless you know what you are doing. It stops the viewport
      // from snapping when text inputs are focused. Ionic handles this internally for
      // a much nicer keyboard experience.
      cordova.plugins.Keyboard.disableScroll(true);
    }
    if(window.StatusBar) {
      StatusBar.styleDefault();
    }
  });
});

app.controller("ExampleController", function($scope, $cordovaFile, $ionicPlatform, $fileFactory, $cordovaPrinter, $cordovaFileOpener2, $interval, $rootScope) {

  $scope.openPDF= function() {
          $cordovaFileOpener2.open(
            fileSystem.name,
            'application/pdf'
          ).then(function() {
              console.log('Success');
          }, function(err) {
          console.log('An error occurred: ' + JSON.stringify(err));
          });
      };

  var fs = new $fileFactory();

  $ionicPlatform.ready(function() {
    fs.getEntriesAtRoot().then(function(result) {
      console.log("result "+ JSON.stringify(result));
      $scope.files = result;
    }, function(error) {
      console.error(error);
    });

    $scope.getContents = function(path) {
      fs.getEntries(path).then(function(result) {
        console.log("result "+JSON.stringify(result));
    //    console.log("result "+result);
        $scope.files = result;
        $scope.files.unshift({name: "[parent]"});
        //funzione per trovare il padre del path corrente
        fs.getParentDirectory(path).then(function(result) {
        //  console.log("result "+result);
          console.log("result "+JSON.stringify(result));
          result.name = "[parent]";
          $scope.files[0] = result;
/*
          $cordovaFileOpener2.open(
          fileSystem.fullPath,
          'application/pdf'
          ).then(function() {
              console.log('Success');
          }, function(err) {
          console.log('An error occurred: ' + JSON.stringify(err));
          });

            deferred.resolve(entries);
          console.log("entries "+ JSON.stringify(entries));
*/

        });
      }, function(error){
        console.error(error);
      });
    }
  });

});


app.factory("$fileFactory", function($q, $cordovaFileOpener2) {

  var File = function() {};

  File.prototype = {

    getParentDirectory: function(path) {
      //questa è la promise
      var deferred = $q.defer();
      //accedo al file local e prendo il path
      window.resolveLocalFileSystemURL(path, function(fileSystem) {
        fileSystem.getParent(function(result) {
          console.log("result "+JSON.stringify(result));
          deferred.resolve(result);
        }, function(error) {
          deferred.reject(error);
        });
      }, function(error) {
        deferred.reject(error);
      });
      return deferred.promise;
    },

    //per trovare tutti i file e cartelle nella root del device
    getEntriesAtRoot: function() {
      var deferred = $q.defer();
      window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function(fileSystem) {
            console.log(fileSystem.name);
        var directoryReader = fileSystem.root.createReader();
        directoryReader.readEntries(function(entries) {
      //    console.log("entries "+entries);
          console.log("result "+ JSON.stringify(entries));
          deferred.resolve(entries);
        }, function(error) {
          deferred.reject(error);
        });
      }, function(error) {
        deferred.reject(error);
      });
      return deferred.promise;
    },

    //per trovare tutti i files e cartelle nel path dato
    getEntries: function(path) {
      var deferred = $q.defer();
      window.resolveLocalFileSystemURL(path, function(fileSystem) {
        console.log(fileSystem.name);
        console.log(fileSystem.fullPath);

        var directoryReader = fileSystem.createReader();
        console.log("directoryReader "+JSON.stringify(directoryReader));
        directoryReader.readEntries(function(entries) {
        //  console.log("entries "+entries);
/*
        $cordovaFileOpener2.open(
        fileSystem.fullPath,
        'application/pdf'
        ).then(function() {
            console.log('Success');
        }, function(err) {
        console.log('An error occurred: ' + JSON.stringify(err));
        });

          deferred.resolve(entries);
        console.log("entries "+ JSON.stringify(entries));
*/
        }, function(error) {
          deferred.reject(error);
        });

      }, function(error) {
        deferred.reject(error);
      });
      return deferred.promise;
    }

  };

  return File;

});