# Class (WebDownloadManager)

Implements a **WebDownloadManager** class. You can use the APIs of this class to resume failed download tasks.

> **NOTE**
>
> - The initial APIs of this module are supported since API version 9. Updates will be marked with a superscript to indicate their earliest API version.
>
> - The initial APIs of this class are supported since API version 11.
>
> - You can preview how this component looks on a real device, but not in DevEco Studio Previewer.

## Modules to Import

```ts
import { webview } from '@kit.ArkWeb';
```

## setDownloadDelegate<sup>11+</sup>

static setDownloadDelegate(delegate: WebDownloadDelegate): void

Sets the delegate used to receive download progress triggered by **WebDownloadManager**.

**System capability**: SystemCapability.Web.Webview.Core

**Parameters**

| Name         | Type   |  Mandatory | Description                                           |
| ---------------| ------- | ---- | ------------- |
| delegate      | [WebDownloadDelegate](./arkts-apis-webview-WebDownloadDelegate.md)  | Yes  | Delegate used to receive the download progress.|

**Example**

```ts
// xxx.ets
import { webview } from '@kit.ArkWeb';
import { BusinessError } from '@kit.BasicServicesKit';

@Entry
@Component
struct WebComponent {
  controller: webview.WebviewController = new webview.WebviewController();
  delegate: webview.WebDownloadDelegate = new webview.WebDownloadDelegate();
  download: webview.WebDownloadItem = new webview.WebDownloadItem();
  failedData: Uint8Array = new Uint8Array();

  build() {
    Column() {
      Button('setDownloadDelegate')
        .onClick(() => {
          try {
            this.delegate.onBeforeDownload((webDownloadItem: webview.WebDownloadItem) => {
              console.log("will start a download.");
              // Pass in a download path and start the download.
              webDownloadItem.start("/data/storage/el2/base/cache/web/" + webDownloadItem.getSuggestedFileName());
            })
            this.delegate.onDownloadUpdated((webDownloadItem: webview.WebDownloadItem) => {
              console.log("download update percent complete: " + webDownloadItem.getPercentComplete());
              this.download = webDownloadItem;
            })
            this.delegate.onDownloadFailed((webDownloadItem: webview.WebDownloadItem) => {
              console.log("download failed guid: " + webDownloadItem.getGuid());
              // Serialize the failed download to a byte array.
              this.failedData = webDownloadItem.serialize();
            })
            this.delegate.onDownloadFinish((webDownloadItem: webview.WebDownloadItem) => {
              console.log("download finish guid: " + webDownloadItem.getGuid());
            })
            this.controller.setDownloadDelegate(this.delegate);
            webview.WebDownloadManager.setDownloadDelegate(this.delegate);
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('startDownload')
        .onClick(() => {
          try {
            this.controller.startDownload('https://www.example.com');
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('resumeDownload')
        .onClick(() => {
          try {
            webview.WebDownloadManager.resumeDownload(webview.WebDownloadItem.deserialize(this.failedData));
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('cancel')
        .onClick(() => {
          try {
            this.download.cancel();
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('pause')
        .onClick(() => {
          try {
            this.download.pause();
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('resume')
        .onClick(() => {
          try {
            this.download.resume();
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Web({ src: 'www.example.com', controller: this.controller })
    }
  }
}
```

## resumeDownload<sup>11+</sup>

static resumeDownload(webDownloadItem: WebDownloadItem): void

Resumes a failed download task.

**System capability**: SystemCapability.Web.Webview.Core

**Parameters**

| Name         | Type   |  Mandatory | Description                                           |
| ---------------| ------- | ---- | ------------- |
| webDownloadItem      | [WebDownloadItem](./arkts-apis-webview-WebDownloadItem.md)  | Yes  | Download task to resume.|

**Error codes**

For details about the error codes, see [Webview Error Codes](errorcode-webview.md).

| Error Code| Error Message                             |
| -------- | ------------------------------------- |
| 17100018 | No WebDownloadDelegate has been set yet. |

**Example**

```ts
// xxx.ets
import { webview } from '@kit.ArkWeb';
import { BusinessError } from '@kit.BasicServicesKit';

@Entry
@Component
struct WebComponent {
  controller: webview.WebviewController = new webview.WebviewController();
  delegate: webview.WebDownloadDelegate = new webview.WebDownloadDelegate();
  download: webview.WebDownloadItem = new webview.WebDownloadItem();
  failedData: Uint8Array = new Uint8Array();

  build() {
    Column() {
      Button('setDownloadDelegate')
        .onClick(() => {
          try {
            this.delegate.onBeforeDownload((webDownloadItem: webview.WebDownloadItem) => {
              console.log("will start a download.");
              // Pass in a download path and start the download.
              webDownloadItem.start("/data/storage/el2/base/cache/web/" + webDownloadItem.getSuggestedFileName());
            })
            this.delegate.onDownloadUpdated((webDownloadItem: webview.WebDownloadItem) => {
              console.log("download update percent complete: " + webDownloadItem.getPercentComplete());
              this.download = webDownloadItem;
            })
            this.delegate.onDownloadFailed((webDownloadItem: webview.WebDownloadItem) => {
              console.log("download failed guid: " + webDownloadItem.getGuid());
              // Serialize the failed download to a byte array.
              this.failedData = webDownloadItem.serialize();
            })
            this.delegate.onDownloadFinish((webDownloadItem: webview.WebDownloadItem) => {
              console.log("download finish guid: " + webDownloadItem.getGuid());
            })
            this.controller.setDownloadDelegate(this.delegate);
            webview.WebDownloadManager.setDownloadDelegate(this.delegate);
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('startDownload')
        .onClick(() => {
          try {
            this.controller.startDownload('https://www.example.com');
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('resumeDownload')
        .onClick(() => {
          try {
            webview.WebDownloadManager.resumeDownload(webview.WebDownloadItem.deserialize(this.failedData));
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('cancel')
        .onClick(() => {
          try {
            this.download.cancel();
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('pause')
        .onClick(() => {
          try {
            this.download.pause();
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Button('resume')
        .onClick(() => {
          try {
            this.download.resume();
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
      Web({ src: 'www.example.com', controller: this.controller })
    }
  }
}
```