title: How to subscribe Ionic 2 platform.pause EventEmitter?
body: <p>I'm trying to use the following code to subscribe, but it doesn't work.</p>
  
  <pre><code>import { Platform } from 'ionic-angular';
  
  @Page({
      templateUrl: 'build/pages/test.html',
  })
  
  export class Test {
  
    constructor(private platform: Platform) {
      this.platform.pause.subscribe(() =&gt; {
        console.log('paused')
      });
    }
  }
  </code></pre>
  
  <p>I'm using Ionic 2 with TypeScript, Angular 2. As <code>platform.pause</code> is an EventEmitter provided by Ionic 2, I suppose it should be able to be subscribed. However, when I put the application to the background, <code>console.log('pause')</code> is not fired.</p>
  
  <p>Should I add <code>Platform</code> to providers or something like that? Plus, this.platform is not <code>null</code>. <code>this.platform.ready().then(()=&gt;{console.log('ready')})</code> works perfectly.</p>