__WEBPACK_IMPORTED_MODULE_1_firebase_app __ .app不是函数

Question

Firebase提供商

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { AngularFireDatabase, FirebaseListObservable } from 'angularfire2/database';

@Injectable() export class FirebaseProvider {
  constructor(public afd: AngularFireDatabase) { }

  getFoodItems() {
    return this.afd.list("/foodItems");
  }

  addFood(foodName) {
    this.afd.list("/foodItems").push(foodName);
  }

  removeFood(id) {
    this.afd.list("/foodItems").remove(id);
  }
}

我在这里使用Firebase提供程序(预定义方法)

import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { StepperPage } from '../stepper/stepper';
import { AboutUsPage } from '../about-us/about-us';
import { FirebaseProvider } from '../../providers/firebase/firebase';
import { FirebaseListObservable } from 'angularfire2/database';

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  foodItems: FirebaseListObservable<any[]>;
  newItem = '';

  constructor(
    public navCtrl: NavController,
    public firebaseProvider: FirebaseProvider
  ) {
    this.foodItems = this.firebaseProvider.getFoodItems();
  }

  addFood() {
    this.firebaseProvider.addFood(this.newItem);
  }

  removeFood(id) {
    this.firebaseProvider.removeFood(id);
  }
}

我得到的错误

错误:未捕获(在承诺中):TypeError:WEBPACK_IMPORTED_MODULE_1_firebase_app .app不是函数TypeError:WEBPACK_IMPORTED_MODULE_1_firebase_app .app不是函数