home.ts

import { LocalNotifications } from '@ionic-native/local-notifications';
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export class HomePage {
  notificationAlreadyReceived = false;

  constructor(
    public backgroundMode: BackgroundMode,
    public platform: Platform,
    public localNotifications: LocalNotifications) {

    platform.ready().then(() => {

      this.backgroundMode.on('activate').subscribe(() => {
        console.log('activated');
        if(this.notificationAlreadyReceived === false) {
          this.showNotification();
        }
      });

      this.backgroundMode.enable();
    })
  }
}