Angular构造函数不执行方法

Question

我试图尽可能地分离我的代码并且我有数据服务，我在构造函数中初始化头文件，但它们没有被设置。

方法是构造函数中的SetHeaders（）。标头没有设置。我是否必须在组件中使用OnInit？

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

import { AuthService } from '../../auth/resourceownerpassword/services/auth.service';

import { environment } from '../../../../environments/environment';

@Injectable()
export class DataService {

    private _endpointUrl: string;
    private _headers: Headers;
    private _options: RequestOptions;
    private _apiEndpoint: string;
    public data: any;

    constructor(public http: Http, public authService: AuthService) {
        this.SetHeaders();
    }

    public SetEndpoint(endpointUrl: string) {
        this._endpointUrl = environment.API_URL + endpointUrl;
    }

    public SetHeaders() {

        console.log('setHeaders started');

        this._headers = new Headers();
        this._headers.append('Content-Type', 'application/json');
        this._headers.append('Accept', 'application/json');

        let token = this.authService.GetToken();

        console.log("Token auth serv: " + token);

        if (token !== '') {
            let tokenValue = 'Bearer ' + token;
            console.log('tokenValue:' + tokenValue);
            this._headers.append('Authorization', tokenValue);
        }

        this._options = new RequestOptions({ headers: this._headers });
    }

    public Get = (): Observable<any[]> => {
        return this.http.get(this._endpointUrl, this._options).map((response: Response) => <any[]>response.json());
    }

    public GetSingle = (id: number): Observable<any> => {
        return this.http.get(this._endpointUrl + '/' + id, this._options).map(res => <any>res.json());
    }

    public Post = (item: any): Observable<any> => {
        return this.http.post(this._endpointUrl, JSON.stringify(item), this._options).map(res => <any>res.json());
    }

    public Put = (item: any): Observable<any> => {
        return this.http.put(this._endpointUrl, JSON.stringify(item), this._options).map(res => <any>res.json());
    }

    public Delete = (id: number): Observable<any> => {
        return this.http.put(this._endpointUrl + '/' + id, null, this._options).map(res => <any>res.json());
    }
}