angular - Angular Service单例构造函数多次调用

我正在尝试使用应用程序范围的服务（user service），该服务存储经过身份验证的用户详细信息。我已经设置了一些路由，但是发现每个路由都实例化了userservice。我希望他们共享相同的用户服务。
我已经创建了一个包含testservice作为提供者的coremodule并将其导入appmodule。
核心模块：

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { TestService } from '../test.service';

@NgModule({
  imports: [
    CommonModule
  ],
  declarations: [],
  providers: [
    TestService
  ]
})
export class CoreModule { }

测试服务：

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

@Injectable({
  providedIn: 'root'
})
export class TestService {
  constructor() { console.log('testService constructor called');}
}

应用模块.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { AdminComponent } from './layout/admin/admin.component';
import { AppComponent } from './app.component';
import { AppRoutingModule } from './app-routing.module';


import { CoreModule } from './core/core.module';

@NgModule({
  declarations: [
    AppComponent,
    AdminComponent,
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    FormsModule,
    CoreModule
  ],
  providers: [
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

app-routing.module.ts程序

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { Routes, RouterModule } from '@angular/router';
import { BasicLoginComponent } from './basic-login/basic-login.component';
import { HttpClientModule } from '@angular/common/http';
import { AdminComponent } from './layout/admin/admin.component';

const routes: Routes = [
  {
    path: '',
    component: AdminComponent,
    children: [
      {
        path: 'home',
        loadChildren: './dashboard/dashboard.module#DashboardModule'
      },
      {
        path: 'user/profile',
        loadChildren: './user-profile/user-profile.module#UserProfileModule'
      }
    ]

  },
]
@NgModule({
  imports: [
    CommonModule,
    RouterModule.forRoot(routes),
    HttpClientModule
  ],
  exports: [
    [RouterModule]
  ],
  declarations: []
})
export class AppRoutingModule { }

我已经将testservice注入到dashboardcomponent和userprofilecomponent构造函数中。但是，当在其中两个组件之间路由时，将调用两次testservice构造函数。
这看起来很直截了当，但不知何故我做不好。有人能给我指一个正确的方向来解决这个问题吗？
*编辑
仪表板.component.ts

import {AfterViewInit, Component, OnInit, ViewEncapsulation} from '@angular/core';
/*import {NotificationsService} from 'angular2-notifications';*/

import { UserService } from '../user.service.js';
import { LocalStorageService } from '../../../node_modules/ngx-webstorage';
import { TestService } from '../test.service.js';

@Component({
  selector: 'app-dashboard',
  templateUrl: './dashboard.component.html',
  styleUrls: ['./dashboard.component.scss'],
  encapsulation: ViewEncapsulation.None
})
export class DashboardComponent implements OnInit, AfterViewInit {


  constructor(private userService:UserService, private localSt:LocalStorageService,
  private testService:TestService) { // private servicePNotify: NotificationsService
  }


  ngOnInit() {

  }

}

用户配置文件组件.ts：

import {Component, OnInit} from '@angular/core';
import {animate, style, transition, trigger} from '@angular/animations';
import {Http} from '@angular/http';
import { TestService } from '../test.service';

@Component({
  selector: 'app-user-profile',
  templateUrl: './user-profile.component.html',
  styleUrls: [
    './user-profile.component.scss',
    '../../assets/icon/icofont/css/icofont.scss'
  ],

})
export class UserProfileComponent implements OnInit {

  constructor(public http: Http, private userService: UserService,
  private testService:TestService) {
  }

  ngOnInit() {

  }

}

最佳答案

因为您已经将testservice声明为-

@Injectable({
  providedIn: 'root'
})

这意味着您将添加到approt模块。
无需在CoreModule中显式添加，因此从CoreModule的提供程序中删除。删除下列内容-

providers: [
    TestService
  ]

当您在TestSevice中添加CoreModule时，它已经在RootModule中添加，这就是它多次被调用的原因。
所以用上面的任何一个。

关于angular - Angular Service单例构造函数多次调用，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/51502757/