我使用动画指定一个提示,以帮助与延迟的交互使用以下：
let delay = 1.8 * Double(NSEC_PER_SEC)
let time = dispatch_time(DISPATCH_TIME_NOW,Int64(delay))
dispatch_after(time,dispatch_get_main_queue()) {
//call the method which have the steps after delay.
self.rain.alpha = 0
UIView.animateWithDuration(5,animations: {
self.rain.alpha = 1
})
self.tip.startAnimating()
}
但是,如果在动画开始之前用户触摸屏幕,我需要停止此延迟过程.
iOS 8和OS X优胜美地引入了dispatch_block_cancel,允许您在开始执行之前取消它们
您在类中声明一个变量,如下所示：
var block: dispatch_block_t?
Init块变量并在dispatch_after中提供：
block = dispatch_block_create(DISPATCH_BLOCK_INHERIT_QOS_CLASS) {
print("I executed")
}
let time: dispatch_time_t = dispatch_time(DISPATCH_TIME_NOW,Int64(5 * NSEC_PER_SEC))
dispatch_after(time,dispatch_get_main_queue(),block!)
之后,您可以取消它如下：
dispatch_block_cancel(block!)
