activities.js

import Ember from 'ember';
const { computed, inject } = Ember;

export default Ember.Service.extend({
  store: inject.service(),
  isPending: computed.readOnly('all.isPending'),
  
  all: computed('store', function() {
    let store = this.get('store');
    return store.find('activity');
  })
});

dashboard.hbs

{{#if activities.isLoaded}}
  {{! Show activities...}}
{{else}}
  {{x-loader}}
{{/if}}

{{! Or... }}

{{#if activities.isUpdating}}
  {{x-loader}}
{{/if}}