HarmonyOS 在Page内使用方法调用方法异常

import { CommonButton } from '../components/CommonButton'; 
import { loadingDialog } from '../components/LoadingDialog'; 
import promptAction from '@ohos.promptAction' 
 
@Entry 
@Component 
struct Index { 
  @State message: string = 'Hello World'; 
  showDialog(){ 
    promptAction.openCustomDialog({ 
      builder: loadingDialog.bind(this,'测试中.....'), 
      isModal: false 
    }).then((dialogId: number) => { 
      this.loadingDialogId = dialogId 
    }) 
  } 
  onClickBtn() { 
    //问题点 
    this.showDialog 
  } 
 
  build() { 
    Row() { 
      CommonButton({ 
        onClickEvent: this.onClickBtn 
      }).height(48) 
        .enabled(true) 
        .width('100%') 
    } 
    .height('100%') 
  } 
 
  loadingDialogId: number = 0; 
 
}