HarmonyOS预加载Image组件的图片

import app, { AppResponse } from '@system.app' 
@Entry 
@Component 
struct Page3 { 
  //app.setImageRawDataCacheSize方法需要在由@Entry标记的页面，onPageShow或aboutToAppear里面设置才生效 
  onPageShow() { 
    // 设置解码前图片数据内存缓存上限为100MB (100MB=100*1024*1024B=104857600B) 
    app.setImageRawDataCacheSize(104857600) 
    console.info('Application onPageShow') 
  } 
  onDestroy() { 
    console.info('Application onDestroy') 
  } 
  @State alt:Resource =$r('app.media.foreground') 
  build() { 
    Row() { 
      Column() { 
        Image($r('')) 
          .onError(()=>{ 
            console.log('demoTest') 
            this.alt = $r('app.media.icon') 
          }) 
          .alt(this.alt) 
          .width(100) 
          .height(100) 
      } 
    } 
  } 
}