Angular2在铬处出现警告XMLHttpRequest

Question

我在Angular2上使用了，但出现了以下警告消息。

不推荐主线程上的同步XMLHttpRequest，因为它会对最终用户的体验产生有害影响。有关更多帮助，请查看

请告诉我怎么做。

http_restful_service.ts

​

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

@Injectable()

export class HTTPRestfulService {

  constructor(private _http: Http) {}

  getAllProjectName() {
    var headers = new Headers();
    headers.append('Content-Type','charset=uft-8');
    return         
       this._http.get('http://localhost/api/database/',
                     {headers: headers})
                 .map(res => res.json());
  }
}

backstage_view.component.ts

import { Component, OnInit } from '@angular/core';
import { HTTPRestfulService } from './../../../service/http_restful_service';

@Component({
    moduleId: module.id,
    selector: 'backstage_view',
    templateUrl: './backstage_view.component.html',
    styleUrls: ['./backstage_view.component.css']
})

export class BackstageViewComponent implements OnInit {

    allProjects: string;

    constructor(private _restfulapi: HTTPRestfulService) {}

    ngOnInit() {     
      this._restfulapi.getAllProjectName()
                      .subscribe(
                        data => this.allProjects = data,
                        error => console.log(error),
                      );
    }
}

Answer 1

为什么不能将内容类型传递为“application/json”格式，

let url= `http://localhost/api/database/`;
    let headers = new Headers();
    headers.append('Content-Type','application/json');
    let params = new URLSearchParams;
    params.append('id', id);
    params.append('user_id', user_id);
    return this.authHttp.post( url,  { headers:headers,  search:params })
   .map(res => res.json());