HarmonyOS webview无法通过loadData加载内容

demo如下

import { webview } from '@kit.ArkWeb';
import { buffer } from '@kit.ArkTS';
import { BusinessError } from '@kit.BasicServicesKit';

@Entry
@Component
struct Sample {
  controller: webview.WebviewController = new webview.WebviewController();

  @State content:string = ''

  aboutToAppear(): void {
    this.content = buffer.from(getContext(this).resourceManager.getRawFileContentSync("index.html")).toString('utf-8')
  }

  build() {
    Column() {
      Text('标题')
        .margin({top:50})

      //可以正常加载
      // Web({ src: $rawfile("index.html"), controller: this.controller })
      //   .layoutWeight(1)

      //无法正常加载
      Web({ src: '', controller: this.controller })
        .layoutWeight(1)
        .onControllerAttached(() => {
          try {
            this.controller.loadData(
              this.content,
              "text/html",
              "UTF-8"
            );
          } catch (error) {
            console.error(`ErrorCode: ${(error as BusinessError).code},  Message: ${(error as BusinessError).message}`);
          }
        })
    }
  }
}