定时器

基础用法

  • 创建新线程(多线程定时器)

  • 创建NSTimer

  • 加入RunLoop

  • 定义执行函数

  • 运行RunLoop(多线程定时器)

实例1

    //  握手部分超时监控
    let handShakerTimeOut: NSTimeInterval = 5
    private var handShakerTimer: NSTimer?
    private func startHandShakerTimer() {
        print("=== startHandShakerTimer ===")
        let thread = NSThread(target: self, selector: Selector("handShakerTimerThreadOperation"), object: nil)
        thread.start()
    }

    @objc private func handShakerTimerThreadOperation() {
        handShakerTimer = NSTimer.scheduledTimerWithTimeInterval(handShakerTimeOut, target: self, selector: "handShakerTimeOutHandler", userInfo: nil, repeats: false)
        if let timer = handShakerTimer {
            NSRunLoop.currentRunLoop().addTimer(timer, forMode: NSDefaultRunLoopMode)
            NSRunLoop.currentRunLoop().run()
        }
    }

    @objc private func handShakerTimeOutHandler() {
        print("=== handShakerTimeOut ===")
        resetInterface()
    }

    private func stopHandShakerTimer() {
        print("=== stopHandShakerTimer ===")
        handShakerTimer?.invalidate()
        handShakerTimer = nil
    }

实例2

    // 统计持续时间
    let unitInterval: NSTimeInterval = 0.5 * 1
    var durationCount: UInt64 = 0
    var duration: NSTimeInterval {
        return unitInterval * NSTimeInterval(durationCount)
    }
    private var durationTimer: NSTimer?
    private func startDurationTimer() {
        let thread = NSThread(target: self, selector: Selector("durationTimerThreadOperation"), object: nil)
        thread.start()
    }

    @objc private func durationTimerThreadOperation() {
        pushTimer = NSTimer.scheduledTimerWithTimeInterval(unitInterval, target: self, selector: "durationTimerHandler", userInfo: nil, repeats: true)
        if let timer = pushTimer {
            print("开始计时")
            durationCount = 0
            NSRunLoop.currentRunLoop().addTimer(timer, forMode: NSRunLoopCommonModes)
            NSRunLoop.currentRunLoop().run()
        }
    }

    @objc private func durationTimerHandler() {
        durationCount++
    }

    private func stopDurationTimer() {
        durationTimer?.invalidate()
        durationTimer = nil
        print("停止计时")
        print("持续时间: \(duration)秒")
    }

主线程定时器

当使用NSTimerscheduledTimerWithTimeInterval方法时。事实上此时Timer会被加入到当前线程的Run Loop中,且模式是默认的NSDefaultRunLoopMode。而如果当前线程就是主线程,也就是UI线程时,某些UI事件,比如UIScrollView的拖动操作,会将Run Loop切换成NSEventTrackingRunLoopMode模式,在这个过程中,默认的NSDefaultRunLoopMode模式中注册的事件是不会被执行的。也就是说,此时使用scheduledTimerWithTimeInterval添加到Run Loop中的Timer就不会执行。

所以为了设置一个不被UI干扰的Timer,我们需要手动创建一个Timer,然后使用NSRunLoopaddTimer:forMode:方法来把Timer按照指定模式加入到Run Loop中。这里使用的模式是:NSRunLoopCommonModes,这个模式等效于NSDefaultRunLoopModeNSEventTrackingRunLoopMode的结合。

例子

    private var timer: NSTimer?
    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)

        print("主线程 \(NSThread.currentThread())")
        //创建Timer, 这两个函数都能用
//        timer = NSTimer(timeInterval: 2, target: self, selector: Selector("timerHandler"), userInfo: nil, repeats: true)
        timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("timerHandler"), userInfo: nil, repeats: true)
        guard let timer = timer else { return }
        //使用NSRunLoopCommonModes模式,把timer加入到当前Run Loop中。
        NSRunLoop.currentRunLoop().addTimer(timer, forMode: NSRunLoopCommonModes)
        print("start timer: \(timer)")
    }

    override func viewWillDisappear(animated: Bool) {
        super.viewWillDisappear(animated)

        print("stop timer: \(timer)")
        timer?.invalidate()
        timer = nil
    }

    //timer的回调方法
    func timerHandler() {
        print("Timer \(NSThread.currentThread())")
    }```
    
## 输出

主线程 {number = 1, name = main}
start timer: <__NSCFTimer: 0x7fa99a5112a0>
Timer {number = 1, name = main}
Timer {number = 1, name = main}
stop timer: Optional(<__NSCFTimer: 0x7fa99a5112a0>)```

多线程定时器

上面讲的NSRunLoopCommonModesTimer中有一个问题,这个Timer本质上是在当前线程的Run Loop中循环执行的,因此Timer的回调方法不是在另一个线程的。那么怎样在真正的多线程环境下运行一个Timer呢?
可以先试试NSThread。同上,我们还是会把Timer加到Run Loop中,只不过这个是在另一个线程中,因此我们需要手动执行Run Loop(通过NSRunLooprun方法)

例子代码

extension WorkThreadViewController {
    // 定时器
    func startTimer() {
        //在当前Run Loop中添加timer,模式是默认的NSDefaultRunLoopMode
        timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("timerHandler"), userInfo: nil, repeats: true)
        guard let timer = timer else { return }
        //使用NSRunLoopCommonModes模式,把timer加入到当前Run Loop中。
        NSRunLoop.currentRunLoop().addTimer(timer, forMode: NSRunLoopCommonModes)
        viewModel?.log = "startTimer(): \(timer)"
        NSRunLoop.currentRunLoop().run()
    }

    //timer的回调方法
    func timerHandler() {
        viewModel?.log = "Timer \(NSThread.currentThread())"
    }

    func stopTimer() {
        viewModel?.log = "stopTimer(): \(timer)"
        timer?.invalidate()
        timer = nil
    }
}

extension WorkThreadViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        viewModel = LogViewModel()
        viewModel?.log = "主线程: \(NSThread.currentThread())"
    }

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)

        //创建并执行新的线程
        let thread = NSThread(target: self, selector: Selector("startTimer"), object: nil)
        thread.start()
        viewModel?.log = "新的线程: \(thread)"
    }

    override func viewWillDisappear(animated: Bool) {
        super.viewWillDisappear(animated)
        
        stopTimer()
    }
}

class WorkThreadViewController: UIViewController {
    
    @IBOutlet weak var logTextView: UITextView!

    private var viewModel: LogViewModel? {
        didSet {
            guard let viewModel = viewModel else { return }

            dispatch_async(dispatch_get_main_queue()) {
                self.logTextView.text = viewModel.logText
            }
        }
    }
    private var timer: NSTimer?
}

struct LogViewModel {
    // ui content
    var logText = "log"

    // action
    var log: String? {
        didSet {
            guard let log = log else { return }
            let message = "[\(NSDate())] \(log)"
            logText = logText + "\(message)\n\t------\t\n"
            print(message)
        }
    }
}
  • extension 将代码分块
  • 用ViewModel隔离显示

输出

[2015-11-10 14:06:35 +0000] 主线程: {number = 1, name = main}
[2015-11-10 14:06:35 +0000] 新的线程: {number = 2, name = main}
[2015-11-10 14:06:35 +0000] startTimer(): <__NSCFTimer: 0x7f8249d3ab50>
[2015-11-10 14:06:37 +0000] Timer {number = 2, name = (null)}
[2015-11-10 14:06:39 +0000] Timer {number = 2, name = (null)}
[2015-11-10 14:06:41 +0000] Timer {number = 2, name = (null)}
[2015-11-10 14:06:42 +0000] stopTimer(): Optional(<__NSCFTimer: 0x7f8249d3ab50>)```

# 后台定时器
要借助苹果上的音频播放类在后台执行的这个特权

# GCD定时器
比较复杂,等遇到了再研究

# 例子代码链接
[一个用Swift写的关于定时器的小Demo](https://github.com/zhangxusong888/TimerDemo)

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