iOS-底层原理 34：界面优化方案

class CJLFPSLabel: UILabel {
    fileprivate var link: CADisplayLink = {
        let link = CADisplayLink.init()
        return link
    }()
    fileprivate var count: Int = 0
    fileprivate var lastTime: TimeInterval = 0.0
    fileprivate var fpsColor: UIColor = {
        return UIColor.green
    }()
    fileprivate var fps: Double = 0.0
    override init(frame: CGRect) {
        var f = frame
        if f.size == CGSize.zero {
            f.size = CGSize(width: 80.0, height: 22.0)
        }
        super.init(frame: f)
        self.textColor = UIColor.white
        self.textAlignment = .center
        self.font = UIFont.init(name: "Menlo", size: 12)
        self.backgroundColor = UIColor.lightGray
        //通过虚拟类
        link = CADisplayLink.init(target: CJLWeakProxy(target:self), selector: #selector(tick(_:)))
        link.add(to: RunLoop.current, forMode: RunLoop.Mode.common)
    }
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    deinit {
        link.invalidate()
    }
    @objc func tick(_ link: CADisplayLink){
        guard lastTime != 0 else {
            lastTime = link.timestamp
            return
        }
        count += 1
        //时间差
        let detla = link.timestamp - lastTime
        guard detla >= 1.0 else {
            return
        }
        lastTime = link.timestamp
        //刷新次数 / 时间差 = 刷新频次
        fps = Double(count) / detla
        let fpsText = "\(String.init(format: "%.2f", fps)) FPS"
        count = 0
        let attrMStr = NSMutableAttributedString(attributedString: NSAttributedString(string: fpsText))
        if fps > 55.0 {
            //流畅
            fpsColor = UIColor.green
        }else if (fps >= 50.0 && fps <= 55.0){
            //一般
            fpsColor = UIColor.yellow
        }else{
            //卡顿
            fpsColor = UIColor.red
        }
        attrMStr.setAttributes([NSAttributedString.Key.foregroundColor: fpsColor], range: NSMakeRange(0, attrMStr.length - 3))
        attrMStr.setAttributes([NSAttributedString.Key.foregroundColor: UIColor.white], range: NSMakeRange(attrMStr.length - 3, 3))
        DispatchQueue.main.async {
            self.attributedText = attrMStr
        }
    }
}

//
//  CJLBlockMonitor.swift
//  UIOptimizationDemo
//
//  Created by 陈嘉琳 on 2020/12/2.
//
import UIKit
class CJLBlockMonitor: NSObject {
    static let share = CJLBlockMonitor.init()
    fileprivate var semaphore: DispatchSemaphore!
    fileprivate var timeoutCount: Int!
    fileprivate var activity: CFRunLoopActivity!
    private override init() {
        super.init()
    }
    public func start(){
        //监控两个状态
        registerObserver()
        //启动监控
        startMonitor()
    }
}
fileprivate extension CJLBlockMonitor{
    func registerObserver(){
        let controllerPointer = Unmanaged<CJLBlockMonitor>.passUnretained(self).toOpaque()
        var context: CFRunLoopObserverContext = CFRunLoopObserverContext(version: 0, info: controllerPointer, retain: nil, release: nil, copyDescription: nil)
        let observer: CFRunLoopObserver = CFRunLoopObserverCreate(nil, CFRunLoopActivity.allActivities.rawValue, true, 0, { (observer, activity, info) in
            guard info != nil else{
                return
            }
            let monitor: CJLBlockMonitor = Unmanaged<CJLBlockMonitor>.fromOpaque(info!).takeUnretainedValue()
            monitor.activity = activity
            let sem: DispatchSemaphore = monitor.semaphore
            sem.signal()
        }, &context)
        CFRunLoopAddObserver(CFRunLoopGetMain(), observer, CFRunLoopMode.commonModes)
    }
    func  startMonitor(){
        //创建信号
        semaphore = DispatchSemaphore(value: 0)
        //在子线程监控时长
        DispatchQueue.global().async {
            while(true){
                // 超时时间是 1 秒，没有等到信号量，st 就不等于 0， RunLoop 所有的任务
                let st = self.semaphore.wait(timeout: DispatchTime.now()+1.0)
                if st != DispatchTimeoutResult.success {
                    //监听两种状态kCFRunLoopBeforeSources 、kCFRunLoopAfterWaiting，
                    if self.activity == CFRunLoopActivity.beforeSources || self.activity == CFRunLoopActivity.afterWaiting {
                        self.timeoutCount += 1
                        if self.timeoutCount < 2 {
                            print("timeOutCount = \(self.timeoutCount)")
                            continue
                        }
                        // 一秒左右的衡量尺度 很大可能性连续来 避免大规模打印!
                        print("检测到超过两次连续卡顿")
                    }
                }
                self.timeoutCount = 0
            }
        }
    }
}

CJLBlockMonitor.share.start()