Angular NG8001 错误。组件只能在一页上运行，不能在其他页面上运行

Question

昨天我完成了我的项目页面之一“home.component”的工作，今天当我想使用其他页面上的一些组件但它们不起作用时，唯一起作用的是“home”和应用程序。组件.html。 错误：

ERROR
src/app/pages/sign-in/sign-in.component.html:2:1 - error NG8001: 'app-header' is not a known element:
1. If 'app-header' is an Angular component, then verify that it is part of this module.
2. If 'app-header' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.

2 <app-header></app-header>
  ~~~~~~~~~~~~

  src/app/pages/sign-in/sign-in.component.ts:5:16
    5   templateUrl: './sign-in.component.html',
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component SignInComponent.

我的文件夹遵循以下顺序：

-- /src
|-- /app
| | -- /core
| | | -- /components
| | | | -- /header
| | | | | -- /header.component.css
| | | | | -- /header.component.html
| | | | | -- /header.component.ts
| | | |
| | | | -- /slider
| | | | | -- /slider.component.css
| | | | | -- /slider.component.html
| | | | | -- /slider.component.ts
| | | 
| | | -- /pages
| | | | -- /home
| | | | | -- /home.component.css
| | | | | -- /home.component.html
| | | | | -- /home.component.ts
| | | |
| | | | -- /sign-in
| | | | | -- /sign-in.component.css
| | | | | -- /sign-in.component.html
| | | | | -- /sign-in.component.ts

header.component.ts

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

@Component({
  selector: 'app-header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.css']
})
export class HeaderComponent {
  title = 'travel-blog';
}

home.component.ts

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

@Component({
  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.css']
})
export class HomeComponent {
  title = 'travel-blog';
}

home.component.html

<app-header></app-header>
/*a bunch of code about this site*/
<app-slider></app-slider>
<app-footer></app-footer>

登录.component.ts

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

@Component({
  selector: 'app-sign-in',
  templateUrl: './sign-in.component.html',
  styleUrls: ['./sign-in.component.css']
})
export class SignInComponent {
  title = 'travel-blog';
}

app.module.ts

import { CUSTOM_ELEMENTS_SCHEMA, NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { RouterModule, Routes } from '@angular/router';
import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { ContactFormComponent } from './core/components/contact-form/contact-form.component';
import { FooterComponent } from './core/components/footer/footer.component';
import { HeaderComponent } from './core/components/header/header.component';
import { SliderComponent } from './core/components/slider/slider.component';
import { AboutUsComponent } from './pages/about-us/about-us.component';
import { AsiaComponent } from './pages/asia/asia.component';
import { EuropeComponent } from './pages/europe/europe.component';
import { ItalyComponent } from './pages/europe/italy/italy.component';
import { SpainComponent } from './pages/europe/spain/spain.component';
import { HomeComponent } from './pages/home/home.component';
import { LastBlogsComponent } from './pages/last-blogs/last-blogs.component';
import { PatreonComponent } from './pages/patreon/patreon.component';
import { SignInComponent } from './pages/sign-in/sign-in.component';
import { SignUpComponent } from './pages/sign-up/sign-up.component';

const appRoutes: Routes = [
  { path: '', component: HomeComponent },
  { path: 'sign-in', component: SignInComponent },
  { path: 'sign-up', component: SignUpComponent },
  { path: 'spain', component: SpainComponent },
  { path: 'italy', component: ItalyComponent },
  { path: 'europe', component: EuropeComponent },
  { path: 'asia', component: AsiaComponent },
  { path: 'last-blogs', component: LastBlogsComponent },
  { path: 'patreon', component: PatreonComponent },
  { path: 'about-us', component: AboutUsComponent },
]

@NgModule({
  declarations: [
    AppComponent,
    HeaderComponent,
    SliderComponent,
    ContactFormComponent,
    FooterComponent,
    HomeComponent
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    RouterModule.forRoot(appRoutes),
  ],
  providers: [],
  bootstrap: [AppComponent],
  schemas: [CUSTOM_ELEMENTS_SCHEMA]
})
export class AppModule { }

app.component.html

<router-outlet></router-outlet>

我认为问题可能出在路由器插座上，因为在 app.component.html 中我可以使用组件。

感谢您的时间和帮助。

我尝试过以下方法：

• 重新启动服务器，关闭终端并使用新终端打开服务器
• 使用确切的路径手动导入组件，但 Angular 没有“找到”它

Answer 1

经验法则是，当您想要使用组件时，您需要在

declarations

列表中定义组件

既然您已经在路线中定义了

SignInComponent

，您应该将其添加到代码中，如下所示

@NgModule({
  declarations: [
    AppComponent,
    HeaderComponent,
    SliderComponent,
    ContactFormComponent,
    FooterComponent,
    HomeComponent,
    SignInComponent // add here
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    RouterModule.forRoot(appRoutes),
  ],
  providers: [],
  bootstrap: [AppComponent],
  schemas: [CUSTOM_ELEMENTS_SCHEMA]
})
export class AppModule { }