无法将navParams从两个单独的页面发送到ionic 2中的另一个页面

import { Injectable } from '@angular/core';

@Injectable()
export class DataSharingService {
  private data: any;

  constructor() { }

  setData(data: any) {
    this.data = data;
  }

  getData() {
    return this.data;
  }
}

import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { DataSharingService } from 'path/to/data-sharing.service';

@Component({
  selector: 'page-sender',
  templateUrl: 'sender.html'
})
export class SenderPage {
  constructor(public navCtrl: NavController, private dataSharingService: DataSharingService) { }

  sendData() {
    let data = { param1: 'value1', param2: 'value2' };
    this.dataSharingService.setData(data);
    this.navCtrl.push(ReceiverPage);
  }
}

import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { DataSharingService } from 'path/to/data-sharing.service';

@Component({
  selector: 'page-receiver',
  templateUrl: 'receiver.html'
})
export class ReceiverPage {
  data: any;

  constructor(public navCtrl: NavController, private dataSharingService: DataSharingService) {
    this.data = this.dataSharingService.getData();
  }
}