Question

尝试在请求进行时实施显示加载指示器的解决方案。从this解决方案看，我使用服务实现了拦截器。一切正常，除了计数器没有减少因为.do()回调永远不会被执行（b永远不会在控制台中打印）。有什么想法吗？如何知道请求是否已经完成？

import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/do';

import { LoadingIndicatorService } from './loading-indicator.service';

@Injectable()
export class LoadingIndicatorInterceptor implements HttpInterceptor {
    constructor(private loadingIndicatorService: LoadingIndicatorService) {}

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

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

      console.log('a');
      handleObs.do(() => {
        console.log('b');
        this.loadingIndicatorService.requestsCount--;
      });

      return handleObs;
    }
}

Answer 1

do（）永远不会被触发，因为你必须返回新的observable。你可以这样做：

export class LoadingIndicatorInterceptor implements HttpInterceptor {
constructor(private loadingIndicatorService: LoadingIndicatorService) {}

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

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

  console.log('a');
  return handleObs.do(() => {
    console.log('b');
    this.loadingIndicatorService.requestsCount--;
  });
}
}

Angular 4 - Observable.do（）的回调不会在拦截器中调用

1 个答案: