我的代码基于以下链接中的示例：

> https://angular.io/guide/http#intercepting-all-requests-or-responses
> Angular4: Using HttpClient’s interceptor to setup a spinner

我的Angular 5应用程序有多个多个模块. HTTP拦截器位于“服务”模块中.

我认为我有一个依赖注入问题,因为当我使用Chrome Dev Tools调试代码时,代码HTTP拦截器代码无法执行.

API-interceptor.ts

import 'rxjs/add/operator/do';
import 'rxjs/add/operator/catch'
import { Observable } from 'rxjs/Observable';
import { Injectable } from '@angular/core';
import {
    HttpEvent,HttpInterceptor,HttpHandler,HttpRequest,HttpResponse
} from '@angular/common/http';
import { Ng4LoadingSpinnerService } from 'ng4-loading-spinner';

@Injectable()
export class ApiInterceptor implements HttpInterceptor {

    private count: number = 0;

    constructor(private spinner: Ng4LoadingSpinnerService) { }

    intercept(req: HttpRequest<any>,next: HttpHandler): Observable<HttpEvent<any>> {
        this.count++;

        if (this.count == 1) this.spinner.show();

        let handleObs: Observable<HttpEvent<any>> = next.handle(req);

        handleObs
            .catch((err: any) => {
                this.count--;
                return Observable.throw(err);
            })
            .do(event => {
                if (event instanceof HttpResponse) {
                    this.count--;
                    if (this.count == 0) this.spinner.hide();
                }
            });

        return handleObs;
    }

}

api.service.ts

import { Injectable,Inject } from '@angular/core';
import { Http,Response,Headers,RequestOptions } from '@angular/http';
import { Observable } from 'rxjs/Observable';

import { TokenService } from './token.service';

@Injectable()
export class ApiService {

    constructor(
        private http: Http,private session: TokenService,@Inject('BASE_URL') private baseUrl) { }

    get(entityRoute: string): Observable<Response> {
        let apiRoute = this.getApiRoute(entityRoute);
        let options = this.generateRequestOptions();

        return this.http.get(apiRoute,options);
    }

    post<T>(entityRoute: string,entity: T): Observable<Response> {
        let apiRoute = this.getApiRoute(entityRoute);
        let options = this.generateRequestOptions();

        return this.http.post(apiRoute,entity,options);
    }

    put<T>(entityRoute: string,options);
    }

    private getApiRoute(entityRoute: string): string {
        return `${this.baseUrl}api/${entityRoute}`;
    }

    private generateRequestOptions(): RequestOptions {
        let headersObj = null;
        let accessToken = this.session.getAccessToken();

        if (accessToken) {
            headersObj = {
                'Content-Type': 'application/json','Authorization': 'Bearer ' + accessToken
            };
        } else {
            headersObj = {
                'Content-Type': 'application/json'
            };
        }

        let headers = new Headers(headersObj);
        return new RequestOptions({ headers: headers });
    }

}

services.module.ts

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { HttpModule } from '@angular/http';
import { Ng4LoadingSpinnerModule } from 'ng4-loading-spinner';

import {
    ApiInterceptor,ApiService,TokenService
} from './index';

@NgModule({
    imports: [
        CommonModule,HttpModule,Ng4LoadingSpinnerModule
    ],providers: [
        ApiInterceptor,TokenService
    ]
})
export class ServicesModule { }

export * from './index';

app.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { Ng4LoadingSpinnerModule } from 'ng4-loading-spinner';

import { BootstrapModule } from './bootstrap/bootstrap.module';
import { ServicesModule,ApiInterceptor } from './services/services.module';
import { AppComponent } from './app-component';

@NgModule({
    bootstrap: [ AppComponent ],imports: [
        BrowserModule,Ng4LoadingSpinnerModule.forRoot(),BootstrapModule,ServicesModule
    ],providers: [
        {
            provide: 'BASE_URL',useFactory: getBaseUrl
        },{
            provide: HTTP_INTERCEPTORS,useClass: ApiInterceptor,multi: true,}
    ]
})
export class AppModule {
}

export function getBaseUrl(): string {
    return document.getElementsByTagName('base')[0].href;
}