错误 NullInjectorError：没有 HttpClient 的提供者：

Question

ERROR NullInjectorError: R3InjectorError(PaceGeneratorLibraryComponentLoader)[HttpClient -> HttpClient -> HttpClient -> HttpClient]: 
  NullInjectorError: No provider for HttpClient!
    at NullInjector.get (core.mjs:6367:27)
    at R3Injector.get (core.mjs:6794:33)
    at R3Injector.get (core.mjs:6794:33)
    at R3Injector.get (core.mjs:6794:33)
    at R3Injector.get (core.mjs:6794:33)
    at ChainedInjector.get (core.mjs:13824:36)
    at lookupTokenUsingModuleInjector (core.mjs:3293:39)
    at getOrCreateInjectable (core.mjs:3338:12)
    at ɵɵdirectiveInject (core.mjs:10879:12)
    at NodeInjectorFactory.DetailsComponent_Factory [as factory] (ɵfac.js? [sm]:1:1)

我在使用HttpClient获取后端数据时遇到了上面的错误。 我已将 HttpModule 包含在我的 NgModule 中，但它似乎不起作用。

@NgModule({
  declarations: [
    AppComponent,
    WidgetContainerComponent
  ],
  exports: [],
  imports: [
    AppRoutingModule,
    BrowserAnimationsModule,
    HttpClientModule,
    BrowserModule,
    ToastrModule.forRoot(),
    ModalModule.forRoot(),
    PlatformCoreBaseModule,
    MsalModule.forRoot(getMsalConfig(environment).msalInstanceConfig, getMsalConfig(environment).msalGuardConfig, undefined),
    
  ],
  providers: [
    AppStateService,
    ClientSettingsService,
    DisplayStateService,
    Title,
    HttpClientModule,
    WebPlatformApiService,
    DynamicComponentLoader,

我已经尝试了几个小时，但对此一无所知。

Answer 1

如果未添加，则在文件顶部使用 import 语句

从'@angular/common/http'导入{HttpClientModule}；

注意：如果我们使用单独的模块，我们还需要导入HttpClientModule

Answer 2

在 imports 数组中而不是在 providers 数组中使用 HttpClientModule：

import { HttpClientModule } from '@angular/common/http';

@NgModule({
  imports: [
    //Module...

    HttpClientModule,
   
  ],
  declarations: [
   //component
  //pipe
 //directive
  ],
 providers :[
 //services...
 ],
 exports :[
 // some components or pipe or directive in the declarations tab
 ]
  bootstrap: [AppComponent]
})