HarmonyOS 鸿蒙Next 自定义组件中，Image控件无法更新图片

设置一个自定义组件:

@Component
struct ImgItem {
  @Prop img: PixelMap | null = null
  @Prop title: string = "测试"

  build() {
    Column() {
      Text(this.title)
      Image(this.img).width(100).height(100).backgroundColor("#f00")
    }
  }
}

在页面使用:

@Entry
@Component
struct Index {
  @State img: PixelMap | null = null
  @State title: string = ""

  fromRawFile(name: string): Promise<PixelMap> {
    let testdata = getContext().resourceManager.getRawFileContentSync(name)
    let imageSource = image.createImageSource(testdata.buffer)
    return imageSource.createPixelMap()
  }

  async aboutToAppear() {
    this.img = await this.fromRawFile("test.jpg")
    this.title = "测试2"
  }

  build() {
    Column() {
      ImgItem({ img: this.img, title: this.title }).margin({ top: 50 })
      Button("更换").onClick(async () => {
        this.img = await this.fromRawFile("test.png")
        this.title = "测试3"
      }).margin({ top: 14 })
    }.height("100%").width("100%")
  }
} 

img无法更新，title可以更新