我尝试使用服务将值从组件保存到Firebase。但是当我使用服务时，我会收到NullInjector错误。我做了所有不属于Internet的事情。导入了所有东西，但它不起作用。我已经尝试导入HttpClientModule，AngularFireDatabase，但没有任何工作。我已经试图完全重新创建该项目的新鲜安装一切。我已经尝试了不同版本的firebase和angular（当前为firebase@7.24.0@angular/fire@6.0.3）。没有任何效果。
这是我的消防服务

import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';

@Injectable({
  providedIn: 'root'
})
export class FireserviceService {

  constructor(private db: AngularFireDatabase) {
    
   }
   create(){
    return this.db.list('/shopping-carts').push({
      dateCreated:new Date().getTime()
    });
  }
}

这是我的应用程序模块

import { FireserviceService } from './fireservice.service';
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { environment } from '../environments/environment';
import { AngularFirestore } from '@angular/fire/firestore';
import { AngularFireModule } from '@angular/fire';
import { AngularFirestoreModule } from '@angular/fire/firestore';
import { BrainComponent } from './brain/brain.component';

@NgModule({
  declarations: [
    AppComponent,
    BrainComponent
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    AngularFireModule.initializeApp(environment.firebase),
    AngularFirestoreModule
  ],
  providers: [
    AngularFirestore,
    FireserviceService
  ],
  bootstrap: [AppComponent]
})
export class AppModule { 
  constructor(){

  }
}

这是我的责任

import { FireserviceService } from './../fireservice.service';
import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'brain',
  templateUrl: './brain.component.html',
  styleUrls: ['./brain.component.css']
})
export class BrainComponent  {

  constructor(private cartService: FireserviceService) { }
  addToCart(val:any){
    console.log(val)
  }

}

这是我得到的错误

core.js:6142 ERROR NullInjectorError: R3InjectorError(AppModule)[FireserviceService -> AngularFireDatabase -> AngularFireDatabase -> AngularFireDatabase]: 
  NullInjectorError: No provider for AngularFireDatabase!
    at NullInjector.get (http://localhost:51081/vendor.js:38768:27)
    at R3Injector.get (http://localhost:51081/vendor.js:38935:33)
    at R3Injector.get (http://localhost:51081/vendor.js:38935:33)
    at R3Injector.get (http://localhost:51081/vendor.js:38935:33)
    at injectInjectorOnly (http://localhost:51081/vendor.js:32465:33)
    at Module.ɵɵinject (http://localhost:51081/vendor.js:32469:61)
    at Object.FireserviceService_Factory [as factory] (http://localhost:51081/main.js:280:159)
    at R3Injector.hydrate (http://localhost:51081/vendor.js:39103:35)
    at R3Injector.get (http://localhost:51081/vendor.js:38924:33)
    at NgModuleRef$1.get (http://localhost:51081/vendor.js:53004:33)

在我向brain组件中的构造函数添加参数之前，网站运行良好，但我一添加私家车服务：大脑组件的构造函数中的FireerviceService甚至不会加载HTML。我是Angular 和firebase的新手。我正在尝试将值保存在firebase数据库中。请帮助。