January 2020
Intermediate to advanced
356 pages
6h 4m
Chinese
Content preview from Swift游戏开发经典实例
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112
｜
第
3
章
有时，你只需要获得用户当前位置，并不想在一段时间内跟踪它的位置。要
想这样，你可以用
CLLocationManager
的
requestLocation
方法：
locationManager.requestLocation()
这样个方法并不会返回一个
location
对象，而是立即返回，只有当它获取到
当前位置后，才会通过委托方法通知你，和你使用
startRequestingLocation
是一样的。二者的不同在于，
requestLocation
得到的是单个的
location
对象，
然后就关闭定位。
3.12
计算运动速度
问题
如何得知用户移动的速度？
解决方案
我们可以利用
Core Location
框架来得到答案。
首先，创建一个
CLLocationManager
，如前一节中所述的一样。然后在接收位置变
化通知的方法中：
func locationManager(_ manager: CLLocationManager,
didUpdateLocations locations: [CLLocation]) {
guard let lastLocation = locations.last else {
return
}
if lastLocation.speed > 0 {
self.speedLabel.text = String(
format: "Currently moving at %.0f meters/second",
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.