Question

需要帮助来建立倒数计时器，该倒数计时器将一直等待直到其无效为止。它也不应阻塞主线程。有提示吗？

private var currentCountdownSeconds = 3
private var countdownTimer = Timer()

private func performTimer() {

    if secondsToCountDown != 0 {
        print(secondsToCountDown)
        countdownTimer = Timer(timeInterval: 1, target: self, selector: #selector(handleCountdown), userInfo: nil, repeats: true)
    }

}

@objc private func handleCountdown() {
    previewView.countdownLabel.text = "\(currentCountdownSeconds)"
    currentCountdownSeconds -= 1
    print(secondsToCountDown)
    if secondsToCountDown == 0 {
        countdownTimer.invalidate()
    }
}

public func toggleMovieRecording() {
    handleTimer()
    videoCaptureLogic()
}

public func toggleCapturePhoto() {
    handleTimer()
    videoCaptureLogic()
}

Answer 1

您可以使用DispatchGroups。在启动计时器时进入组，在计时器无效时离开组。

private var currentCountdownSeconds = 3
private var countdownTimer = Timer()
private let timerDispatchGroup = DispatchGroup() // Init DispatchGroup

private func performTimer() {

    if secondsToCountDown != 0 {
        print(secondsToCountDown)
        timerDispatchGroup.enter() // Enter DispatchGroup
        countdownTimer = Timer(timeInterval: 1, target: self, selector: #selector(handleCountdown), userInfo: nil, repeats: true)
    }

}

@objc private func handleCountdown() {
    previewView.countdownLabel.text = "\(currentCountdownSeconds)"
    currentCountdownSeconds -= 1
    print(secondsToCountDown)
    if secondsToCountDown == 0 {
        countdownTimer.invalidate()
        timerDispatchGroup.leave() // Leave DispatchGroup
    }
}

public func toggleMovieRecording() {
    performTimer() // I guess it should be performTimer instead of handleTimer?
    timerDispatchGroup.notify(queue: .main) { videoCaptureLogic() } // Closure 
}

public func toggleCapturePhoto() {
    performTimer()
    timerDispatchGroup.notify(queue: .main) { videoCaptureLogic() }
}

Answer 2

如果您必须在多个地方使用倒数计时，请尝试此操作。

private var currentCountdownSeconds = 3
private var countdownTimer = Timer()

private func performTimer() {

    if secondsToCountDown != 0 {
        print(secondsToCountDown)
        countdownTimer = Timer(timeInterval: 1, target: self, selector: #selector(handleCountdown), userInfo: nil, repeats: true)
    }

}

@objc private func handleCountdown() {
    previewView.countdownLabel.text = "\(currentCountdownSeconds)"
    currentCountdownSeconds -= 1
    print(secondsToCountDown)
    if secondsToCountDown == 0 {
        countdownTimer.invalidate()
        NotificationCenter.default.post(notification: NSNotification.Name.init("TimeComplete")
    }
}

现在在您需要的任何类中实现通知的观察者。当倒计时完成并发布通知时，相应的选择器将处理事件。

class Something {

    init() {
        NotificationCenter.default.addObserver(self, selector: #selector(timerCompleteAction), name: NSNotification.Name.init("TimerComplete"), object: nil)
    }

    @objc func timerCompleteAction() {
          //Do necessary actions
    }
}

Something可以是您的具有视频捕获功能的课程，在这种情况下，请将该代码写入timerCompleteAction。然后再次在具有音频捕获功能的类中，添加相同的观察者并添加选择器方法，然后执行音频捕获操作。

进行倒数计时-快速

2 个答案: