需求：实现一个时间打卡签到按钮。

实现方法：每隔一秒钟获取一下当前时间。

实现代码如下：

Column(){
  Text(this.curTime)
    .fontColor('#FFFFFF')
    .fontWeight(600)
    .fontSize('32vp')
  Text('上班打卡')
    .fontColor('#FFFFFF')
}
.width('170vp')
.height('170vp')
.justifyContent(FlexAlign.Center)
.alignItems(HorizontalAlign.Center)
.backgroundImage($r('app.media.check_signin'))
.backgroundImageSize({ width: StyleConstants.FULL_PARENT,height: StyleConstants.FULL_PARENT })

@State curTime:string | null = null;
@State time:number | null = null;

// 更新时间
updateTime(){
  const now = new Date();
  const hours = String(now.getHours()).padStart(2, '0');
  const minutes = String(now.getMinutes()).padStart(2, '0');
  const time = `${hours}:${minutes}` as string;
  this.curTime = time;
}

aboutToAppear():void {
  this.updateTime();
  // 每秒更新一次时间
  this.time = setInterval(()=>{
    this.updateTime()
  }, 1000);
}
aboutToDisappear():void {
  // 清除定时器
  clearInterval(this.time)
}