ERROR Error: StaticInjectorError(AppModule)[UserformService -> HttpClient]:

问题

While trying to add a PrimeNG table I broke my build here: https://github.com/BillyCharter87/Tech-O-Dex-UI/tree/BrokeIt

I recall updating my package.json from TypeScript 2.3.4 to 2.4.0 and it broke due to (I think) the fact that I was using Headers and Http for my POST call. I tried setting it back to 2.3.4 to no avail. I have fixed what I could by adding in:

import { HttpClient, HttpHeaders } from "@angular/common/http";

but still running into the Error I have now for the HttpClient. I have tried importing HttpClient into the providers like so: providers: [HttpClient] for my app.module.ts.

The full error is as follows:

AppComponent.html:9 ERROR Error: StaticInjectorError(AppModule)[HttpClient -> HttpHandler]: 
StaticInjectorError(Platform: core)[HttpClient -> HttpHandler]: 
NullInjectorError: No provider for HttpHandler!

回答1:

Add

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

to app.module.ts file. That fixed my problem.

回答2:

Make sure you have imported HttpClientModule instead of adding HttpClient direcly to the list of providers.

See https://angular.io/guide/http#setup for more info.

The HttpClientModule actually provides HttpClient for you. See https://angular.io/api/common/http/HttpClientModule:

Sample code:

import { HttpClientModule, /* other http imports */ } from "@angular/common/http";

@NgModule({
    // ...other declarations, providers, entryComponents, etc.
    imports: [
        HttpClientModule,
        // ...some other imports
    ],
})
export class AppModule { }

回答3:

Import this in to app.module.ts

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

and add this one in imports

HttpClientModule

回答4:

In my case there was a need for:

@Injectable({
    providedIn: 'root'  // <- ADD THIS
})
export class FooService { ...

instead of just:

@Injectable()
export class FooService { ...

回答5:

Simply i have import in appmodule.ts

import { HttpClientModule } from '@angular/common/http';
  imports: [
     BrowserModule,
     FormsModule,
     HttpClientModule  <<<this 
  ],

My problem resolved

回答6:

provide all custom services means written by you in component decorator section Example : providers: [serviceName]

note:if you are using service for exchanging data between components. declare providers: [serviceName] in module level

回答7:

There are two possible reasons 1. If you are using HttpClient in your service you need to import HttpClientModule in your module file and mention it in the imports array.

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

If you are using normal Http in your services you need to import HttpModule in your module file and mention it in the imports array.

import { HttpModule } from '@angular/http'

By default, this is not available in the angular then you need to install @angular/http

If you wish you can use both HttpClientModule and HttpModule in your project.

回答8:

import the HttpClientModule in your app.module.ts

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

...
@NgModule({
...
  imports: [
    //other content,
    HttpClientModule
  ]
})

回答9:

There are two reasons for this error

1) In the array of import if you imported HttpModule twice

2) If you haven't import:

import { HttpModule, JsonpModule } from '@angular/http';

If you want then run:

npm install @angular/http

来源：https://stackoverflow.com/questions/50013398/error-error-staticinjectorerrorappmoduleuserformservice-httpclient

标签

angular

angular4-httpclient