HarmonyOS 调用数据打印出来都是空的,是什么原因

可以参考下面的demo输出数据：

import { HashMap } from '@kit.ArkTS';
@Entry
@Component
struct CallDataEmptyDemo {
  @State message: string = 'Hello World';
  aboutToAppear(): void {
    console.log('开始输出数据---------------')
    console.log('tag-----', demo.getTipAlertImage('key1').get('key1'))
  }
  build() {
    Row() {
      Column() {
        Text(this.message)
          .fontSize(50)
          .fontWeight(FontWeight.Bold)
      }
      .width('100%')
    }
    .height('100%')
  }
}
class demo{
  public static getTipAlertImage(alertStr: string): HashMap<string, string> {
    let result: HashMap<string, string>= new HashMap<string, string>();
    result.set( 'key1' , '远离广告牌');
    result.set( 'key2', '远离树木');
    return result;
  }
}