HarmonyOS如何从对话框获取用户返回结果？

import promptAction from '@kit.ArkUI';  
import { BusinessError } from '@kit.BasicServicesKit';  
@Entry  
@Component  
struct Index {  
  build() {  
    Row() {  
      Column() {  
        Text('Dialog')  
          .fontSize(50)  
          .fontWeight(FontWeight.Bold)  
          .onClick(() => {  
            this.onBackClick();  
          })  
      }  
      .width('100%')  
    }  
    .height('100%')  
  }  
  async onBackClick(): Promise<number> {  
    let result = -1;  
    try {  
      let data = await promptAction.showDialog({//data是个对象  
        title: '标题',  
        message: '内容',  
        buttons: [  
          {  
            text: 'A',  
            color: '#000000',  
          },  
          {  
            text: 'B',  
            color: '#000000',  
          }  
        ],  
      })  
      console.log("index是：" + data.index)//index是数字0和1  
      result=data.index  
    } catch (error) {  
    }  
    console.log("result是：" + result)  
    return result;  
  }  
}