Question

Angular 2中是否有一种方法可以使用angular2 / http模块检索ajax调用的进度（即完成百分比）？

我使用以下代码进行HTTP调用：

        let body = JSON.stringify(params);
        let headers = new Headers({ 'Content-Type': 'application/json' });
        let options = new RequestOptions({ headers: headers });
        this.http.post(url, body, options)
            .timeout(10000, new Error('Timeout exceeded during login'))
            .toPromise()
            .then((res) => {
                ...
            }).catch((err) => {
                ...
            });

目标是编写同步系统。该帖子将返回大量数据，我想让用户了解同步需要多长时间。

Answer 1

目前（从版本4.3.0开始，当使用来自HttpClient的新@ngular/common/http时）Angular提供了开箱即用的收听进度。您只需要创建HTTPRequest对象，如下所示：

import { HttpRequest } from '@angular/common/http';
...

const req = new HttpRequest('POST', '/upload/file', file, {
  reportProgress: true,
});

当您订阅请求时，您将在每个进度事件中收到订阅：

http.request(req).subscribe(event => {
  // Via this API, you get access to the raw event stream.
  // Look for upload progress events.
  if (event.type === HttpEventType.UploadProgress) {
    // This is an upload progress event. Compute and show the % done:
    const percentDone = Math.round(100 * event.loaded / event.total);
    console.log(`File is ${percentDone}% uploaded.`);
  } else if (event instanceof HttpResponse) {
    console.log('File is completely uploaded!');
  }
});

更多信息here。

Answer 2

您可以利用XHR提供的onprogress事件（请参阅此plunkr：http://plnkr.co/edit/8MDO2GsCGiOJd2y2XbQk?p=preview）。

这样可以获得有关下载进度的提示。 Angular2不支持此功能，但您可以通过扩展BrowserXhr类来插入它：

@Injectable()
export class CustomBrowserXhr extends BrowserXhr {
  constructor(private service:ProgressService) {}
  build(): any {
    let xhr = super.build();
    xhr.onprogress = (event) => {
      service.progressEventObservable.next(event);
    };
    return <any>(xhr);
  }
}

并使用扩展名覆盖BrowserXhr提供程序：

bootstrap(AppComponent, [
  HTTP_PROVIDERS,
  provide(BrowserXhr, { useClass: CustomBrowserXhr })
]);

有关详细信息，请参阅此问题：

Angular2 / RxJS - updating variable after getting data from Http observable

Answer 3

当你在angular2中创建http cals时，它会返回一个类型为Response的Observable，这个响应是在名为XHRConnection的类中创建的，其中所有的魔法都会发生。

XHRConnection通过监听 XMLHttpRequest的加载事件来构建响应，这意味着它将在请求结束时返回一个响应。

现在为了能够改变这种行为，我们需要让我们的连接类听取进度事件。

因此我们需要创建自定义Connection类，以便按照我们认为合适的方式处理响应。

我是这样做的， 请注意我的php API在单个请求中返回多个响应，并且此响应是纯字符串。

<强> my_backend.ts

import {Injectable} from "angular2/core";
import {Observable} from "rxjs/Observable";
import {Observer} from "rxjs/Observer";
import {Connection,ConnectionBackend} from "angular2/src/http/interfaces";
import {ReadyState, RequestMethod, ResponseType} from "angular2/src/http/enums";
import {ResponseOptions} from "angular2/src/http/base_response_options";
import {Request} from "angular2/src/http/static_request";
import {Response} from "angular2/src/http/static_response";
import {BrowserXhr} from "angular2/src/http/backends/browser_xhr";
import {Headers} from 'angular2/src/http/headers';
import {isPresent} from 'angular2/src/facade/lang';
import {getResponseURL, isSuccess} from "angular2/src/http/http_utils"

export class MyConnection implements Connection { 
    readyState: ReadyState;
    request: Request;
    response: Observable<Response>;

    constructor(req: Request, browserXHR: BrowserXhr, baseResponseOptions?: ResponseOptions) {       
        this.request = req;
        this.response = new Observable<Response>((responseObserver: Observer<Response>) => {
            let _xhr: XMLHttpRequest = browserXHR.build();
            _xhr.open(RequestMethod[req.method].toUpperCase(), req.url);
            // save the responses in array 
            var buffer :string[] = []; 
            // load event handler
            let onLoad = () => {
                let body = isPresent(_xhr.response) ? _xhr.response : _xhr.responseText;
                //_xhr.respons 1 = "Loading data!"
                //_xhr.respons 2 = "Loading data!Ready To Receive Orders."
                // we need to fix this proble 
                // check if the current response text contains the previous then subtract
                // NOTE: I think there is better approach to solve this problem.
                buffer.push(body);
                if(buffer.length>1){
                    body = buffer[buffer.length-1].replace(buffer[buffer.length-2],'');
                }
                let headers = Headers.fromResponseHeaderString(_xhr.getAllResponseHeaders());
                let url = getResponseURL(_xhr);
                let status: number = _xhr.status === 1223 ? 204 : _xhr.status;
                let state:number = _xhr.readyState;
                if (status === 0) {
                    status = body ? 200 : 0;
                }
                var responseOptions = new ResponseOptions({ body, status, headers, url });
                if (isPresent(baseResponseOptions)) {
                    responseOptions = baseResponseOptions.merge(responseOptions);
                }
                let response = new Response(responseOptions);
                //check for the state if not 4 then don't complete the observer
                if(state !== 4){
                    //this will return stream of responses
                    responseObserver.next(response);
                    return;
                }
                else{
                    responseObserver.complete();
                    return;
                }
                responseObserver.error(response);
            };
            // error event handler
            let onError = (err: any) => {
                var responseOptions = new ResponseOptions({ body: err, type: ResponseType.Error });
                if (isPresent(baseResponseOptions)) {
                    responseOptions = baseResponseOptions.merge(responseOptions);
                }
                responseObserver.error(new Response(responseOptions));
            };

            if (isPresent(req.headers)) {
                req.headers.forEach((values, name) => _xhr.setRequestHeader(name, values.join(',')));
            }
            _xhr.addEventListener('progress', onLoad);
            _xhr.addEventListener('load', onLoad);
            _xhr.addEventListener('error', onError);

            _xhr.send(this.request.text());

            return () => {
                _xhr.removeEventListener('progress', onLoad);
                _xhr.removeEventListener('load', onLoad);
                _xhr.removeEventListener('error', onError);
                _xhr.abort();
            };
        });
    }
}
@Injectable()
export class MyBackend implements ConnectionBackend {
  constructor(private _browserXHR: BrowserXhr, private _baseResponseOptions: ResponseOptions) {}
  createConnection(request: Request):MyConnection {
    return new MyConnection(request, this._browserXHR, this._baseResponseOptions);
  }
}

在 app.component.ts

中

import {Component, provide} from 'angular2/core';
import {HTTP_PROVIDERS,XHRBackend} from 'angular2/http';
import {MyBackend} from './my_backend';
@Component({
    selector: 'my-app',
    providers:  [
        HTTP_PROVIDERS,
        MyBackend,
        provide(XHRBackend, {useExisting:MyBackend})
    ]
    .
    .
    .

现在调用http.get会返回一些响应。

Answer 4

我强烈建议使用此

https://www.npmjs.com/package/angular-progress-http

否则用xhr搞乱会让你错过会话cookie和其他东西

除了它更便于携带，更容易实现

Answer 5

@Bartek Chichoki的回答是正确的，但不适用于我的情况。添加观察：“事件”对我来说很成功

const req = new HttpRequest('POST', '/upload/file', file, {
  reportProgress: true,
  observe: 'events'
});

希望有帮助

Angular 2 HTTP进度条

5 个答案: