UIScrollView滚动时，Timer不失效的方法
1、改变当前RunLoop的mode
let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { (timer) in
//code
}
RunLoop.current.add(timer, forMode: .commonModes)
2、在主线程中定义Timer
DispatchQueue.main.async {
let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { (timer) in
//code
}
RunLoop.current.run()
}
3、在子线程中定义Timer
DispatchQueue.global().async {
let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { (timer) in
//code 若有UI操作，需要回到主线程
}
RunLoop.current.add(timer, forMode: .defaultRunLoopMode)
RunLoop.current.run()
}
