Angular2 - 'router-outlet' is not a known element

Question

I created routes with deep child paths. I added <router-outlet> to the AdminComponent component which I wrapped into NgModule. But after refreshing the page I got this error:

'router-outlet' is not a known element

Maybe it occurred because I forgot import some module to admin.module.ts

Please help. Thanks.

app.routes.ts

export const routes: Routes = [
    {
        path: '',
        component: AppComponent,
        children: [
            {
                path: '',
                component: LoginComponent
            },
            {
                path: 'admin',
                component: AdminComponent
            },
            {
                path: 'user',
                component: UserComponent
            },
            {
                path: 'there',
                component: ThereComponent
            }
        ]
    }
]

app.module.ts

@NgModule({
    imports: [
        BrowserModule,
        AppRoutes,
        FormsModule,
        ReactiveFormsModule,
        HttpModule,
        RouterModule,
        TranslateModule.forRoot({
            provide: TranslateLoader,
            useFactory: (http: Http) => {
                return new TranslateStaticLoader(http, './src/assets/i18n', '.json')
            },
            deps: [Http]
        }),
        UserComponentModule,
        AdminComponentModule,
        LoginComponentModule,
        ThereComponentModule,
        DashboardComponentModule
    ],
    declarations: [
        AppComponent
    ],
    providers: [
        FormBuilder
    ],
    bootstrap: [AppComponent]
})

admin.component.ts and admin.module.ts

//  admin.component.ts
import {Component} from "@angular/core";

@Component({
    selector: 'admin',
    template: "<router-outlet></router-outlet>",
})

export class AdminComponent {
    constructor() {

    }
}

//  admin.module.ts
const ADMIN_DECLARATION = [
    AdminComponent
];

@NgModule({
    imports: [
        BrowserModule,
        TranslateModule,
        FormsModule,
        ReactiveFormsModule
    ],
    declarations: [
        ADMIN_DECLARATION
    ],
    exports: [
        ADMIN_DECLARATION
    ],
    providers: [
        TranslateService,
        FormBuilder
    ]
})

export class AdminComponentModule {

}

Answer 1

AdminComponent is part of AdminComponentModule and you have not imported RouterModule inside AdminComponentModule module:

//  admin.component.ts
import {Component} from "@angular/core";

@Component({
    selector: 'admin',
    template: "<router-outlet></router-outlet>",
})

export class AdminComponent {
    constructor() {

    }
}

//  admin.module.ts
const ADMIN_DECLARATION = [
    AdminComponent
];

@NgModule({
    imports: [
        BrowserModule,
        TranslateModule,
        RouterModule,
        FormsModule,
        ReactiveFormsModule
    ],
    declarations: [
        ADMIN_DECLARATION
    ],
    exports: [
        ADMIN_DECLARATION
    ],
    providers: [
        TranslateService,
        FormBuilder
    ]
})

export class AdminComponentModule {

}