问题
I have this block of code:
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)
}
Now, I want to be able to stop this thread from executing. How can I stop it from being executed? For instance, after 3 seconds, I decide I don't want that to execute anymore so I want to stop it.
回答1:
You can use DispatchWorkItem
s. They can be scheduled on DispatchQueue
s and cancelled before their execution.
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()
回答2:
You could use an one-shot DispatchSourceTimer
rather than 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()
and cancel the execution with
oneShot?.cancel()
oneShot = nil
来源:https://stackoverflow.com/questions/44633729/stop-a-dispatchqueue-that-is-running-on-the-main-thread