Swift 计时器滞后

Question

我知道 Timer 不能保证运行完全符合您要求的速度。但是，我刚刚开始了一个全新的项目：

class ViewController: NSViewController {

    var timer = Timer()
    var count: Double = 0.0
    var timeStamp: Date = Date()

override func viewDidLoad() {
    super.viewDidLoad()
    self.timer = Timer.scheduledTimer(timeInterval: 0.1,
                                      target: self,
                                      selector: #selector(self.updateCounting),
                                      userInfo: nil,
                                      repeats: true)
}

@objc func updateCounting(){
    let duration = self.timeStamp.distance(to: Date())
    print("Counting \(self.count) vs. Real life \(duration)")
    self.count = self.count + 0.1
}

}

我希望在 count 和 duration 之间得到大致相同的结果，但我看到了这样奇怪的事情：

Counting 60.50000000000059 vs. Real life 60.64057409763336
Counting 60.60000000000059 vs. Real life 60.741435050964355
Counting 60.70000000000059 vs. Real life 70.84065008163452
Counting 60.800000000000594 vs. Real life 80.94094407558441
Counting 60.900000000000595 vs. Real life 82.99448704719543

在 Xcode 11.5、iMac 和 MacBook Pro 上测试。我是不是做错了什么？

Answer 1

没看错，但您错过了 Mac 应用的能效指南：

您的应用正在休眠。

检查 ProcessInfo 并搜索 管理活动。一个例子（不好的例子）是将你的 AppDelegate.swift 更改为：

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {
    private var activity: NSObjectProtocol!

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        let options: ProcessInfo.ActivityOptions = [.userInitiatedAllowingIdleSystemSleep]
        let reason = "No napping!"
        self.activity = ProcessInfo.processInfo.beginActivity(options: options, reason: reason)
    }

    func applicationWillTerminate(_ aNotification: Notification) {
        ProcessInfo.processInfo.endActivity(activity)
    }
}

但是不要这样做，对用户不好，MacBook Pro 电池寿命等

Swift 计时器滞后

Swift Timer lags

swift

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nstimer