Angular 5.2自定义HttpClient类-无法将responseType更改为blob

现在我想把responseType改成blob来下载excel文件,但它对我不起作用。

在我的项目中,我创建了包装类CustomHttpClient来进行Get或Post调用。

CustomHttpClient类如下所示:-

    export interface IRequestOptions {

    headers?: HttpHeaders;
    observe?: 'body';
    params?: HttpParams;
    reportProgress?: boolean;
    responseType?: 'json';
    withCredentials?: boolean;
    body?: any;
}


/*Custom HttpClient Class for making the WebAPI calls.*/
export class CustomHttpClient {

    _defaultHeaderType = new HttpHeaders({ 'Content-Type': 'application/json' });

    // Extending the HttpClient through the Angular DI.
    public constructor(public _http: HttpClient) {

    }

  public Get<T>(endPoint: string, options?: IRequestOptions): Observable<T> {
        if (options == undefined) {
            options = <IRequestOptions>{};
            options.headers = this._defaultHeaderType
        }

        options.headers = this.injectClient(options.headers);
        return this._http.get<T>(endPoint, options);
    }

    public GetBlob<T>(endPoint: string, options?: IRequestOptions): Observable<T> {
        if (options == undefined) {
            options = <IRequestOptions>{};
            options.headers = this._defaultHeaderType
        }

        //This line is giving error
         options.responseType = 'blob';

        options.headers = this.injectClient(options.headers);
        return this._http.get<T>(endPoint, options);
    }
}

在组件服务类中,我这样调用fn:-

downloadTemplate(): Observable<any> {
    let opt = {
        headers: new HttpHeaders({ 'Content-Type': 'application/json', 'Accept': 'application/xlsx'}),
        options: new RequestOptions({ responseType: ResponseContentType.Blob })
    }

    return this._httpObj.GetBlob(this._baseUrl + 'DownloadTemplate', opt);
}