要回答原始问题:

Android O上似乎没有内置的方法来获取ForegroundService的单行和正在进行的通知.可以尝试添加自定义设计，但是由于不同的手机具有不同的通知设计，因此该解决方案并不是一个很好的解决方案.

There seems to be no built-in way on Android O to get a single line, ongoing notification for a ForegroundService. One could try adding a custom design, but as different phones have different designs for notification, that solution is hardly a good one.

但是还是有希望的:)

在 Android P 上，将NotificationChannel中的IMPORTANCE_LOW中优先级为PRIORITY_LOW 的通知压缩为单个行，即使对于ForegroundService.是的！

On Android P the notification in a NotificationChannel of IMPORTANCE_LOW with a priority of PRIORITY_LOW is compacted to a single line even for a ForegroundService. Yeah!!