HarmonyOS webview加载数据问题

请看以下代码，只有setTimeout和点击按钮才能正常设置数据，onPageShow和aboutToAppear里面点用都不行，是什么原因呢，我在onPageShow和aboutToAppear里面调用web_webview.once也不行

import hilog from '@ohos.hilog'
import web_webview from '@ohos.web.webview';
@Entry
@Component
struct cs {
  controller: web_webview.WebviewController = new web_webview.WebviewController();

  callback: (obj: keyValue) => void = (obj: keyValue) => {
  }

  aboutToAppear() {

    setTimeout(() => {
      this.controller.loadData(
        "setTimeout___________________________",
        "text/html",
        "UTF-8"
      );
    }, 500)
    this.controller.loadData(
      "aboutToAppear_______________________aboutToAppear",
      "text/html",
      "UTF-8"
    );
  }
  onPageShow(): void {
    this.controller.loadData(
      "onPageShow____________________________",
      "text/html",
      "UTF-8"
    );
  }

  
  build() {
    Column() {
      Button('loadData')
        .onClick(() => {
          try {
            this.controller.loadData(
              "loadData______________________",
              "text/html",
              "UTF-8"
            );
          } catch (error) {
          }
        })
      Web({ src: 'www.huawei.com', controller: this.controller }).onTitleReceive((event) => {

      })
    }
    .backgroundColor($r('app.color.bg_color'))
    .width('100%')
    .height('100%')
  }
}