---
name: "DownloadTask.onHeadersReceived"
mode: "kit"
versionRequirements:
  - { name: "BaseKit", version: "2.0.1" }
platform:
  - "iOS"
  - "Android"
title: "DownloadTask.onHeadersReceived - 监听 HTTP Response Header 事件。会比请求完成事件更早"
---

## DownloadTask.onHeadersReceived

> [VERSION] BaseKit >= 2.0.1

> [PLATFORM] iOS, Android

### 描述

监听 HTTP Response Header 事件。会比请求完成事件更早

### 参数

`(listener: Function)`

| 参数 | 类型 | 必填 | 默认值 | 描述 |
| --- | --- | --- | --- | --- |
| `listener` | `(params: Object) => void` | 是 | - | 事件监听回调函数 |

##### DownloadTask.onHeadersReceived.listener(params) 的属性

| 属性 | 类型 | 必填 | 默认值 | 最低版本 | 描述 |
| --- | --- | --- | --- | --- | --- |
| `header` | `Record<string, string>` | 是 | - | `2.0.1` | 开发者服务器返回的 HTTP Response Header |
| `requestId` | `string` | 是 | - | `2.0.1` | 网络请求id |


### 示例代码

#### Demo

```tsx
import { downloadFile } from '@ray-js/ray'

// 监听响应头：先用 ty.downloadFile 拿到下载任务句柄，再在句柄上注册 headers 监听。
const downloadTask = await downloadFile({
  url: "https://airtake-public-data-1254153901.cos.ap-shanghai.myqcloud.com/ttttestfile/test_video.mp4",
});

downloadTask.onHeadersReceived(e => {
  console.log(e);
});
```