在Angular 2中获取系统小时更改事件

Question

我希望在系统小时更改时得到通知。从上午9点到上午10点或下午5点到6点。基本上在我的应用程序中，我想按小时更改显示。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方式，以便系统小时自动更改时我可以得到通知。

Answer 1

没有建立服务的angular2，但你可以创建自己的。

下面是一个简单服务来演示如何可以做到：

@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