Question

我有这段代码：

    DispatchQueue.main.asyncAfter(deadline: .now() + (delay * Double(isDelayAccounted.hashValue)) + extraDelay) {
        self.isShootingOnHold = false
        self.shoot()
        self.shootingEngine = Timer.scheduledTimer(timeInterval: (Double(60)/Double(self.ratePerMinute)), target: self, selector: #selector(ShootingEnemy.shoot), userInfo: nil, repeats: true)   
    }

现在，我希望能够阻止此线程执行。怎么能阻止它被执行？例如，3秒后，我决定不再执行这样的操作了，所以我想阻止它。

Answer 1

您可以使用DispatchWorkItem s。它们可以在DispatchQueue进行安排，并在执行前取消。

let work = DispatchWorkItem(block: {
    self.isShootingOnHold = false
    self.shoot()
    self.shootingEngine = Timer.scheduledTimer(timeInterval: (Double(60)/Double(self.ratePerMinute)), target: self, selector: #selector(ShootingEnemy.shoot), userInfo: nil, repeats: true)
})
DispatchQueue.main.asyncAfter(deadline: .now() + (delay * Double(isDelayAccounted.hashValue)) + extraDelay, execute: work)
work.cancel()

Answer 2

您可以使用一次性DispatchSourceTimer而不是asyncAfter

var oneShot : DispatchSourceTimer!

 oneShot = DispatchSource.makeTimerSource(queue: DispatchQueue.main)
 oneShot.scheduleOneshot(deadline: .now() + (delay * Double(isDelayAccounted.hashValue)) + extraDelay))
 oneShot.setEventHandler {
     self.isShootingOnHold = false
     self.shoot()
     self.shootingEngine = Timer.scheduledTimer(timeInterval: (Double(60)/Double(self.ratePerMinute)), target: self, selector: #selector(ShootingEnemy.shoot), userInfo: nil, repeats: true)   
 }
 oneShot.setCancelHandler {
     // do something after cancellation
 }

 oneShot.resume()

并使用

取消执行

oneShot?.cancel()
oneShot = nil

停止在主线程上运行的DispatchQueue

2 个答案: