RxSwift中timer不受runloop的影響可以正常計時，以下探索timer實現原理。
Timer
- swift創建timer
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
timer = Timer.init(timeInterval: 1, target: self, selector: #selector(timerFire), userInfo: nil, repeats: true)
RunLoop.current.add(timer, forMode: .default)
}
@objc func timerFire() {
print(NSDate())
}
/*
輸出結果：
2019-08-04 10:27:38 +0000
2019-08-04 10:27:39 +0000
2019-08-04 10:27:40 +0000
2019-08-04 10:27:41 +0000
2019-08-04 10:27:42 +0000
……
*/
- 當頁面有滾動事件時定時器會停止計時，滾動事件結束定時器繼續計時。
- 把定時器加到Runloop的
.commonMode中，滾動事件不影響定時器計時，但是在commonMode裏執行會影響整個程序，且不容易處理
- Timer.scheduledTimer的寫法
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerFire), userInfo: nil, repeats: true)
- Timer.scheduledTimer的寫法在頁面有滾動事件時定時器會停止計時，說明此方法加進了runloop的
.defaultMode裏
DispatchSourceTimer
- swift創建gcdTimer
gcdTimer = DispatchSource.makeTimerSource()
gcdTimer?.schedule(deadline: DispatchTime.now(), repeating: DispatchTimeInterval.seconds(1))
gcdTimer?.setEventHandler(handler: {
print("gcdTimer:\(NSDate())")
})
gcdTimer?.resume()
/*
輸出結果：
gcdTimer:2019-08-04 11:18:13 +0000
gcdTimer:2019-08-04 11:18:14 +0000
gcdTimer:2019-08-04 11:18:15 +0000
gcdTimer:2019-08-04 11:18:16 +0000
gcdTimer:2019-08-04 11:18:17 +0000
……
*/
- gcdTimer，滾動事件不影響定時器計時，這種方式計時更準確有效
- gcdTimer操作
gcdTimer?.suspend() //掛起，gcdTimer掛起後一定要取消置空
gcdTimer?.cancel() //取消，先取消再置空
gcdTimer = nil //置空
CADisplayLink
- swift創建cadTimer
cadTimer = CADisplayLink(target: self, selector: #selector(timerFire))
cadTimer?.preferredFramesPerSecond = 1
cadTimer?.add(to: RunLoop.current, forMode: .default)
- cadTimer也是加入到runloop的
.defaultMode裏，滾動事件時定時器會停止計時
RxSwift timer
- RxSwift創建timer
Observable<Int>.interval(1, scheduler: MainScheduler.instance).subscribe(onNext: { (num) in
print(num)
})
.disposed(by: disposeBag)
- RxSwift的timer計時不受滑動時間影響，底層是封裝了GCD執行計時
- interval的實現
public static func interval(_ period: RxTimeInterval, scheduler: SchedulerType)
-> Observable<Element> {
return Timer(
dueTime: period,
period: period,
scheduler: scheduler
)
}
-
Timer類的實現
Timer類繼承於Producer，執行run方法，run方法裏創建TimerSink
/*繼承於Producer，執行run方法，Producer裏的run方法由子類來實現*/
final private class Timer<Element: RxAbstractInteger>: Producer<Element> {
fileprivate let _scheduler: SchedulerType
fileprivate let _dueTime: RxTimeInterval
fileprivate let _period: RxTimeInterval?
// 初始化
init(dueTime: RxTimeInterval, period: RxTimeInterval?, scheduler: SchedulerType) {
self._scheduler = scheduler //調度環境
self._dueTime = dueTime //定時器發起事件
self._period = period //間隔時間
}
//執行run方法
override func run<Observer: ObserverType>(_ observer: Observer, cancel: Cancelable) -> (sink: Disposable, subscription: Disposable) where Observer.Element == Element {
if self._period != nil {
//創建TimerSink，然後執行sink.run
let sink = TimerSink(parent: self, observer: observer, cancel: cancel)
let subscription = sink.run()
return (sink: sink, subscription: subscription)
}
else {
let sink = TimerOneOffSink(parent: self, observer: observer, cancel: cancel)
let subscription = sink.run()
return (sink: sink, subscription: subscription)
}
}
}
- TimerSink，init初始化，實現run方法
final private class TimerSink<Observer: ObserverType> : Sink<Observer> where Observer.Element : RxAbstractInteger {
typealias Parent = Timer<Observer.Element>
private let _parent: Parent
private let _lock = RecursiveLock()
init(parent: Parent, observer: Observer, cancel: Cancelable) {
self._parent = parent
super.init(observer: observer, cancel: cancel)
}
func run() -> Disposable {
//執行schedulePeriodic方法
return self._parent._scheduler.schedulePeriodic(0 as Observer.Element, startAfter: self._parent._dueTime, period: self._parent._period!) { state in
self._lock.lock(); defer { self._lock.unlock() }
self.forwardOn(.next(state))
return state &+ 1
}
}
}
- schedulePeriodic方法，創建了GCD計時器並處理定時器回調
func schedulePeriodic<StateType>(_ state: StateType, startAfter: RxTimeInterval, period: RxTimeInterval, action: @escaping (StateType) -> StateType) -> Disposable {
let initial = DispatchTime.now() + startAfter
var timerState = state
// 創建GCD計時器
let timer = DispatchSource.makeTimerSource(queue: self.queue)
timer.schedule(deadline: initial, repeating: period, leeway: self.leeway)
// TODO:
// This looks horrible, and yes, it is.
// It looks like Apple has made a conceputal change here, and I'm unsure why.
// Need more info on this.
// It looks like just setting timer to fire and not holding a reference to it
// until deadline causes timer cancellation.
var timerReference: DispatchSourceTimer? = timer
let cancelTimer = Disposables.create {
timerReference?.cancel()
timerReference = nil
}
//定時器回調，保存的定時器事件
timer.setEventHandler(handler: {
//容錯條件
if cancelTimer.isDisposed {
return
}
//發送狀態
timerState = action(timerState)
})
timer.resume()
return cancelTimer
}
- action是閉包的傳值，往上找可以在TimerSink的run方法找到action的實現，action裏執行self.forwardOn(.next(state))發送消息，也就是執行subscribe(onNext:)方法返回到閉包裏執行打印
func run() -> Disposable {
return self._parent._scheduler.schedulePeriodic(0 as Observer.Element, startAfter: self._parent._dueTime, period: self._parent._period!) { state in //尾隨閉包action實現
self._lock.lock(); defer { self._lock.unlock() }
self.forwardOn(.next(state))
return state &+ 1 //按位與操作，地址+1，改變狀態
}
}
- timer序列停止計時
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
//timer已經加入到disposeBag裏，這裏將disposeBag重新賦值即可銷燬timer停止計時
disposeBag = DisposeBag()
}