注入服务时遇到StaticInjectorError（AppModule）[Boolean]

Question

我正在尝试使用angular创建一个具有登录页面的简单应用程序。我希望单例服务保存登录数据，并且希望该服务由应用程序组件使用。尝试在构造函数中实例化服务时，我始终收到相同的错误。

这是app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from "@angular/forms";
import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { LoginPageComponent } from './login-page/login-page.component';
import { NavHeaderComponent } from './nav-header/nav-header.component';
import {LoginService} from "./login.service";
@NgModule({
declarations: [
AppComponent,
LoginPageComponent,
NavHeaderComponent
],
imports: [
BrowserModule,
AppRoutingModule,
FormsModule
],
bootstrap: [AppComponent]
})
export class AppModule { }

这是app.component.ts

import { Component } from '@angular/core';
import { LoginService } from "./login.service";
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss'],
})
export class AppComponent {
private title : string = '*******';
private isLoggedIn : Boolean ;
constructor(loginService : LoginService){
this.isLoggedIn = loginService.CheckLoginStatus();
}
}

这是服务 login.service.ts

import { Injectable } from '@angular/core';
@Injectable({
 providedIn: 'root'
})
export class LoginService {
private username = "***";
private password = "***";
private isLogin : Boolean = false;
// Variable to check whether the user has logged in or not
constructor(isLogin:Boolean) {
this.isLogin = isLogin;
}
/* Function to check login status */
CheckLoginStatus()   {
return this.isLogin;
}
/* Function to call after the user is logged in */
HasLoggedIn()   {
this.isLogin = true;
}
/* Function to call after the user is logged out */
HasLoggedOut()   {
this.isLogin = false;
}
/*Function to validate User */
validateLogin(username : string , password : string)
{
if(username===this.username && password===this.password)
this.HasLoggedIn();
return this.isLogin;
}
}

= 这里出了什么问题？