web拦截并替换图片，有谁知道怎么处理？

import { webview } from '@kit.ArkWeb'; 
import { common } from '@kit.AbilityKit'; 
import fs from '@ohos.file.fs'; 
import axios from '@ohos/axios'; 
 
@Entry 
@Component 
struct GetFile { 
  @State message: string = 'Hello World'; 
  // 获取应用文件路径 
  context = getContext(this) as common.UIAbilityContext; 
  webviewController: webview.WebviewController = new webview.WebviewController(); 
  responseweb: WebResourceResponse = new WebResourceResponse() 
 
  aboutToAppear() { 
    // 配置Web开启调试模式 
    webview.WebviewController.setWebDebuggingAccess(true); 
  } 
 
  hasFile(filePath: string) { 
    let b = fs.accessSync(filePath) 
    return b 
  } 
 
  async getFile(url: string) { 
    // const regex = new RegExp('/[^/]+/g', 'gim'); 
    // console.log(url+" 123456") 
    // const fileName = url.match(regex); 
    const fileName = url.split("/").pop(); 
    console.log(fileName + " 123456") 
    const filePath = this.context.cacheDir + '/' + fileName; 
    console.log(filePath + ' 123456') 
    const flag = this.hasFile(filePath); 
    console.log(flag + "123456") 
    if (!flag) { 
      await this.downloadImage(url, filePath); 
    } 
    // const fd : number = await fileio.open(filePath); 
    let file = fs.openSync(filePath, fs.OpenMode.READ_ONLY); 
    console.log(file + "1234567") 
    let arrayBuffer = new ArrayBuffer(4096); 
    console.log(file.fd + " 123456") 
    return file.fd; 
  } 
 
  async downloadImage(url: string, filePath: string) { 
    try { 
      await axios({ 
        method: "get", 
        url, 
        context: this.context, 
        filePath: filePath 
      }); 
    } catch (error) { 
      console.error('[Demo] axios error'); 
    } 
  } 
 
  build() { 
    Column() { 
      Web({ src: $rawfile('catch.html'), controller: this.webviewController }) 
        .onInterceptRequest((event) => { 
          if (event) { 
            console.log('url123456:' + event.request.getRequestUrl()) 
          } 
          const url = event!.request.getRequestUrl(); 
          // const regExp = new RegExp("^(http|https)[w/-]+(.jpg)$"); 
          console.log(url.endsWith(".jpg") + '123456') 
          if (!url.endsWith(".jpg")) return null; 
          try { 
            // const responseweb = new WebResourceResponse(); 
            let url2 = 'https://img.tukuppt.com/photo-big/17/12/16/57/94/171216579483.jpg'; 
            this.getFile(url2).then(fd => { 
              this.responseweb.setResponseData(fd); 
              this.responseweb.setResponseCode(200); 
              this.responseweb.setReasonMessage('OK'); 
              this.responseweb.setResponseIsReady(true); 
              console.log(fd + " 1234567") 
            }); 
            this.responseweb.setResponseMimeType('image/*'); 
            this.responseweb.setResponseIsReady(false); 
            console.log(this.responseweb.getResponseData().toString + "123456") 
            return this.responseweb; 
          } catch (error) { 
            console.error(`[Demo]Code: ${error.code},Message: ${error.message} `); 
            return null 
          } 
        }) 
    } 
  } 
}