HarmonyOS 鸿蒙Next里web如何实现长按保存图片到相册

最终用web的长按监听，获取长按控件的src实现了

Web({
  src: 'https://www.baidu.com',
  controller: this.webViewController
})

.onContextMenuShow((event) => {
  if (event) {
    let mediaType = event.param.getMediaType()
    let hitValue = this.webViewController.getHitTestValue()
    this.imgBase64 = hitValue.extra
    //长按的是图片，且图片是base64的，因getSourceUrl没取到，用extra取到了
    if (mediaType === ContextMenuMediaType.Image &&
    this.imgBase64.startsWith("data:image")) {
      this.showMenu = true
    }
  }
  return false
})
.bindPopup(this.showMenu,
  {
    builder: this.menuBuilder(),
    enableArrow: false,
    placement: Placement.TopLeft,
    mask: false,
    offset: { x: 0, y: 0 },
    onStateChange: (e) => {
      if (!e.isVisible) {
        this.showMenu = false;
        this.result?.closeContextMenu();
      }
    }
  })

/**
 * 因下载图片需要savebutton，增加下载图片确认弹窗，包含savebutton
 */
@Builder
function menuBuilder() {
  Column() {
    Text('您确定要下载该图片吗？')
      .fontSize(18)
      .fontWeight(FontWeight.Regular)
      .margin({ top: 20, bottom: 15 })

    Row() {
      Button('取消')
        .height(44)
        .backgroundColor($r('app.color.color_white'))
        .fontColor($r('app.color.color_77849E'))
        .borderColor($r('app.color.color_DEE3EF'))
        .borderWidth(1)
        .borderRadius(22)
        .width('45%')
        .onClick(() => {
          this.showMenu = false;
        })

      Blank().width(10)

      SaveButton()
        .width('45%')
        .height(44)
        .borderRadius(22)
        .backgroundColor($r('app.color.color_007AFF'))
        .onClick(async (event: ClickEvent, result: SaveButtonOnClickResult) => {
          if (result === SaveButtonOnClickResult.SUCCESS) {
            let arr = this.imgBase64.split(",")
            if (arr.length > 0) {
              let base64 = arr[arr.length-1] as string
              ImageUtil.base64ImageSaveToGallery(base64)
            }
            this.showMenu = false;
          }
        })
    }
    .margin({ top: 20, bottom: 20 })
    .justifyContent(FlexAlign.Center)
  }
  .width('80%')
  .backgroundColor(Color.White)
  .borderRadius(10)
}