角4-使用HttpModule我得到了错误“没有提供ConnectionBackend!”

Question

我是Angular4 (和TypeScript)的新手，我一直在犯这个错误：

我的app.module.ts设置如下：

import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';
import { HttpModule } from '@angular/http';

import { AppComponent }  from './app.component';
import { CustomerListComponent }  from './Customer-List/customer-list.component';
import { CustomerDetailsComponent }  from './Customer-Details/customer-details.component';
import { DataService } from './services/data.service';


@NgModule({
  imports:      [ BrowserModule, FormsModule, HttpModule ],
  declarations: [ AppComponent, CustomerListComponent, CustomerDetailsComponent ],
  providers: [ DataService ],
  bootstrap:    [ AppComponent ]
})
export class AppModule { }

我有一个服务(称为DataService)，它在以下代码中使用Http模块：

    import { Injectable } from '@angular/core';
    import { Http, Response, RequestOptions, Headers } from '@angular/http';
    import { CreateTestCustomers } from '../data/test-data';
    import { Customer } from '../Models/customerModel';

    @Injectable()
    export class DataService {

        private customersUrl = 'http://localhost:52740/api/Customers/';

        constructor(
            private http : Http
        ) { }

        getCustomersP() : Promise<Customer[]>{
                const customers = CreateTestCustomers();

                return this.http.get(this.customersUrl)
                    .toPromise()
                    .then(response => {
                        const custs = response.json().data as Customer[];
                        return custs;
                    }, error => {
                        return Promise.reject('Something bad happened, please check the console');
                    },);
            }
    }

当我试图编译我的应用程序时，我会发现一个奇怪的错误：

Unhandled Promise rejection: No provider for ConnectionBackend! ; Zone: <root> ; Task: Promise.then ; Value: Error: No provider for ConnectionBackend! Error: No provider for ConnectionBackend!
   at ReflectiveInjector_.prototype._throwOrNull (eval code:2681:13)
   at ReflectiveInjector_.prototype._getByKeyDefault (eval code:2720:13)
   at ReflectiveInjector_.prototype._getByKey (eval code:2652:13)
   at ReflectiveInjector_.prototype.get (eval code:2521:9)
   at resolveNgModuleDep (eval code:9513:5)
   at _createClass (eval code:9555:13)
   at _createProviderInstance$1 (eval code:9524:13)
   at resolveNgModuleDep (eval code:9508:13)
   at _createClass (eval code:9555:13)
   at _createProviderInstance$1 (eval code:9524:13)
zone.js (661,17)
   "Unhandled Promise rejection:"
   "No provider for ConnectionBackend!"
   "; Zone:"
   "<root>"
   "; Task:"
   "Promise.then"
   "; Value:"
   {
      [functions]: ,
      __proto__: { },
      __zone_symbol__currentTask: { },
      description: "No provider for ConnectionBackend!",
      injectors: [ ],
      keys: [ ],
      message: "No provider for ConnectionBackend!",
      name: "Error",
      ngDebugContext: { },
      ngOriginalError: undefined,
      stack: "Error: No provider for ConnectionBackend!
   at ReflectiveInjector_.prototype._throwOrNull (eval code:2681:13)
   at ReflectiveInjector_.prototype._getByKeyDefault (eval code:2720:13)
   at ReflectiveInjector_.prototype._getByKey (eval code:2652:13)
   at ReflectiveInjector_.prototype.get (eval code:2521:9)
   at resolveNgModuleDep (eval code:9513:5)
   at _createClass (eval code:9555:13)
   at _createProviderInstance$1 (eval code:9524:13)
   at resolveNgModuleDep (eval code:9508:13)
   at _createClass (eval code:9555:13)
   at _createProviderInstance$1 (eval code:9524:13)"
   }
   "Error: No provider for ConnectionBackend!
   at ReflectiveInjector_.prototype._throwOrNull (eval code:2681:13)
   at ReflectiveInjector_.prototype._getByKeyDefault (eval code:2720:13)
   at ReflectiveInjector_.prototype._getByKey (eval code:2652:13)
   at ReflectiveInjector_.prototype.get (eval code:2521:9)
   at resolveNgModuleDep (eval code:9513:5)
   at _createClass (eval code:9555:13)
   at _createProviderInstance$1 (eval code:9524:13)
   at resolveNgModuleDep (eval code:9508:13)
   at _createClass (eval code:9555:13)
   at _createProviderInstance$1 (eval code:9524:13)"

以前有人遇到过这种情况吗？在线上的每件事似乎都提到了角2，而且对它的任何修正似乎都没有帮助角4。

我看过这篇文章，但它没有得到解答--我的问题看起来很相似：angular 4 Error: Uncaught (in promise): Error: No provider for ConnectionBackend! while injecting Jsonp

提前感谢！

Answer 1

与其说是一个答案，不如说是一个解决办法。我搭建了一个新的项目，并将我的组件一个接一个地加入进来，以解决这个问题。不知道原来的项目是怎么回事。