页面加载前获取网络图片的宽高

import image from '@ohos.multimedia.image'; 
 
@Entry 
@Component 
struct Index { 
  @State message: string = 'Hello World'; 
 
  @State _pixelMap: image.PixelMap | undefined = undefined; 
  @State with: number = 0 
  @State hig: number = 0 
 
  async aboutToAppear() { 
    console.error(" aboutToAppear start."); 
    let resourceManager = getContext(this).resourceManager; 
    let imageArray = await resourceManager.getMediaContent($r('app.media.startIcon')); 
    let imageResource = image.createImageSource(imageArray.buffer); 
    let opts: image.DecodingOptions = { editable: true } 
    this._pixelMap = await imageResource.createPixelMap(opts); 
    this._pixelMap.getImageInfo().then((imageInfo : image.ImageInfo) => { 
      if (imageInfo == undefined) { 
        console.error("Failed to obtain the image pixel map information."); 
      } 
      this.with = imageInfo.size.width; 
      this.hig = imageInfo.size.height; 
      console.log(" Succeeded in obtaining the image pixel map information.", this.with, this.hig); 
    }) 
    console.error(" aboutToAppear end."); 
  } 
 
  build() { 
    Row() { 
      Column() { 
        Text(this.message) 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
      } 
      .width(this.with) 
      .height(this.hig) 
      .backgroundColor(Color.Green) 
    } 
    .height('100%') 
  } 
}