Question

我希望在系统小时更改时收到通知。喜欢从上午9点到10点或下午5点到下午6点。基本上在我的应用程序中，我想每小时更改显示。我知道我可以通过手动计算来获得更改。我只是好奇有没有其他办法，所以当系统时间自动改变时我会收到通知。

Answer 1

没有angular2内置服务，但您可以创建自己的。

这是一个简单的服务，用于演示如何完成它：

@Injectable()
class TimeNotifyService {

  private _lastHour;
  private _lastMinute;
  private _lastSecond;

  public hourChanged = new Subject<number>();
  public minuteChanged = new Subject<number>();
  public secondChanged = new Subject<number>();

  constructor() {
    setTimeout(() => this.timer(), 2000); // just a delay to get first hour-change..
  }

  private timer() {
    const d = new Date();
    const curHour = d.getHours();
    const curMin = d.getMinutes();
    const curSec = d.getSeconds();

    if (curSec != this._lastSecond) {
      this.secondChanged.next(curSec);
      this._lastSecond = curSec;
    }

    if (curMin != this._lastMinute) {
      this.minuteChanged.next(curMin);
      this._lastMinute = curMin;
    }

    if (curHour != this._lastHour) {
      this.hourChanged.next(curHour);
      this._lastHour = curHour;
    }

    // timeout is set to 250ms JUST to demonstrate the seconds-change..
    // if only hour-changes are needed, there is NO reason to check that often ! :)
    setTimeout(() => this.timer(), 250);
  }
}

现场演示：https://plnkr.co/edit/QJCSnlMKpboteXbIYzqt?p=preview

在Angular 2中获取系统小时更改事件

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