Question

我必须显示从当前Date（）到结束Date（）的超时。但是当应用程序处于后台时，计时器不会更新。我尝试了BackgroundTask方法，但最多只能工作3分钟。还有其他方法吗？

        self.timer = Timer.scheduledTimer(timeInterval: 1.0, target: weakSelf, selector: #selector(self.setTimeLeft), userInfo: nil, repeats: true)
func setTimeLeft() {
    let timeNow = Date()

    // Only keep counting if timeEnd is bigger than timeNow
    if timeEnd.compare(timeNow as Date) == ComparisonResult.orderedDescending {
        let calendar = Calendar.current
        let components = calendar.dateComponents([.day, .hour, .minute, .second], from: timeNow, to: timeEnd)
        guard let day = components.day, let hours = components.hour,let minute = components.minute , let seconds = components.second else { return }
        var dayText = String(day) + "d "
        var hourText = String(hours) + "h "

        // Hide day and hour if they are zero
        if day <= 0 {
            dayText = ""
            if hours <= 0 {
                hourText = ""
            }
        }
        self.countDownTimeLabel.text = dayText + hourText + String(minute) + "m " + String(seconds) + "s"

    } else {
        self.countDownTimeLabel.text = "Game Over!"
    }
}

Answer 1

应用不会在后台持续运行，除非明确允许应用（例如音频播放器或GPS）。此外，如果应用程序在后台，用户也不会看到标签更改。

我建议在计时器间隔结束时安排本地通知。操作系统会在合适的时间将其提供给用户。

此外，将目标时间存储在NSUserDefaults中。当您的应用再次启动时，请将其与当前时间进行比较，以确定是否需要更新标签。

App在后台时的计时器

1 个答案: