Ion-refresher-content nothing shown

Here is the code:

 <ion-refresher (ionRefresh)="doRefresh($event)">
  <ion-refresher-content pullingIcon="arrow-dropdown" pullingText="{{ 'PULL_TO_REFRESH' | translate }}" refreshingSpinner="circles" refreshingText="{{ 'REFRESHING' | translate }}">
  </ion-refresher-content>                    
 </ion-refresher>

But nothings are shown, anyone know what is the problem?
My ionic info:

cli packages:

@ionic/cli-plugin-cordova       : 1.5.0 (/Users/nulra/Downloads/proj3/node_modules/@ionic/cli-plugin-cordova)
@ionic/cli-plugin-ionic-angular : 1.4.0 (/Users/nulra/Downloads/proj3/node_modules/@ionic/cli-plugin-ionic-angular)
@ionic/cli-utils                : 1.6.0 (/Users/nulra/Downloads/proj3/node_modules/@ionic/cli-utils)
ionic (Ionic CLI)               : 3.6.0 (/Users/nulra/Downloads/proj3/node_modules/ionic)

global packages:

Cordova CLI : 7.0.1 

local packages:

@ionic/app-scripts : 2.0.2
Cordova Platforms  : browser 4.1.0 ios 4.4.0
Ionic Framework    : ionic-angular 3.5.2