HarmonyOS 自定义Dialog背景色透明问题

import {promptAction} from '@kit.ArkUI'; 
 
@Builder 
function Loading() { 
 LoadingProgress() 
  .backgroundColor('rgba(0,0,0,0.6)') 
  .color('#ffffff') 
  .width(60) 
} 
 
@Entry 
@Component 
struct Example { 
 build() { 
  Column(){ 
   Button('Ok').onClick(()=>{ 
    promptAction.openCustomDialog({ 
     builder: Loading.bind(this), 
     alignment: DialogAlignment.Center, 
     isModal: false 
    }) 
   }) 
  } 
 } 
}