HarmonyOS 按下返回键时，如何禁止CustomDialog退出

import { common } from '@kit.AbilityKit' 
 
@Entry 
@Component 
struct CustomDialogPage { 
 @Provide("isShowed") isShowed: boolean = false 
 @Provide("ifBanBack") ifBanBack: boolean = true 
 
 /** * 通过该方法设置返回键以及侧边栏的禁用与否 * @returns */ 
 onBackPress() { 
  return this.ifBanBack 
 } 
 
 build() { 
  Column() { 
   Button('点击操作弹窗').onClick(() => { 
    this.isShowed = !this.isShowed 
   }).visibility(this.isShowed ? Visibility.None : Visibility.Visible) 
   CustomExample().visibility(this.isShowed ? Visibility.Visible : Visibility.None) 
  }.width('100%').height('100%').justifyContent(FlexAlign.Center) 
 } 
} 
 
@Component 
struct CustomExample { 
 @Consume("isShowed") isShowed: boolean 
 @Consume("ifBanBack") ifBanBack: boolean 
 
 build() { 
  Column() { 
   Text('This is the setting of textOverflow to Clip text content This is the setting of textOverflow to None text content. This is the setting of textOverflow to Clip text content This is the setting of textOverflow to None text content.') 
   Blank() 
   Row() { 
    Button("拒绝").width(100).onClick(() => { 
     const context = getContext(this) as common.UIAbilityContext; 
     context.terminateSelf() //退出app 
    }) 
    Button('接受').width(100).onClick(() => { 
     this.isShowed = false 
     this.ifBanBack = false 
    }) 
   }.width('100%').justifyContent(FlexAlign.SpaceAround).padding({ bottom: 10 }) 
  }.width('90%').height('70%').backgroundColor('#D5D5D5').borderRadius(10) 
 } 
}