为何静电注入错误

Question

我正在制作Angular 2应用程序。我尝试使用php从数据库获取数据。它给出了这样的错误。这是我的第一个角应用程序

ERROR Error: StaticInjectorError(AppModule)[UserService -> HttpClient]: 
  StaticInjectorError(Platform: core)[UserService -> HttpClient]: 
    NullInjectorError: No provider for HttpClient!
    at _NullInjector.get (core.js:1002)
    at resolveToken (core.js:1300)
    at tryResolveToken (core.js:1242)
    at StaticInjector.get (core.js:1110)
    at resolveToken (core.js:1300)
    at tryResolveToken (core.js:1242)
    at StaticInjector.get (core.js:1110)
    at resolveNgModuleDep (core.js:10854)
    at _createClass (core.js:10891)
    at _createProviderInstance$1 (core.js:10865)


import { Injectable } from '@angular/core';
import 'rxjs/add/operator/map';
import { HttpClientModule } from '@angular/common/http';
import {Http} from '@angular/http';



@Injectable()
export class UserService {
  employees = [];
  checkMe: any;
  constructor(private http: Http) { }

  getUsers() {
    return this.http.get('http://localhost/Wedima/wedima-app/api/select.php')
      .map(res => {
        this.checkMe = res;
        if (this.checkMe._body !== '0') {
          return res;
        }
      });
  }

}

这是我的用户service.ts文件。

import { Component, OnInit } from '@angular/core';
import {UserService} from '../user.service';
import {ActivatedRoute, Params, Router} from '@angular/router';
import { NgIf } from '@angular/common';
import { User } from '../user';

@Component({
  selector: 'app-sitemain',
  templateUrl: './sitemain.component.html',
  styleUrls: ['./sitemain.component.css']
})
export class SitemainComponent implements OnInit {
  users: any;
  constructor(private _User: UserService,
              private router: Router) {
  }

  ngOnInit() {
    this.getUsers();
  }

  getUsers() {
    this._User
      .getUsers()
      .subscribe(users => {
        this.users = users;
      } );
  }

}

这是我访问user.service文件的地方。我不知道错误来自哪里我尝试了很多例子。但没有什么是Happen

我怎样才能修复它。我尝试了很多例子，但我无法修复它。

Answer 1

你在app.module.ts中缺少HttpClientModule

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

和

@NgModule({
    ...
    imports: [HttpClientModule]
    ...
})