1裂明、什么是RunLoop

故名思義就是偶芍，運(yùn)行循環(huán), 在程序運(yùn)行過程中循環(huán)做一些事情拌禾。iOS中有2套API來訪問和使用RunLoop取胎。

• Foundation：NSRunLoop
• CFRunLoopRef：CFRunLoopRef
• NSRunLoop和CFRunLoopRef都代表著RunLoop對(duì)象
• NSRunLoop是基于CFRunLoopRef的一層OC包裝
• CFRunLoopRef是開源的。
• https://opensource.apple.com/tarballs/CF

2、RunLoop與線程關(guān)系

• 每條線程都有唯一的一個(gè)與之對(duì)應(yīng)的RunLoop對(duì)象
• RunLoop保存在一個(gè)全局的Dictionary里闻蛀，線程作為key匪傍，RunLoop作為value
• 線程剛創(chuàng)建時(shí)并沒有RunLoop對(duì)象，RunLoop會(huì)在第一次獲取它時(shí)創(chuàng)建
• RunLoop會(huì)在線程結(jié)束時(shí)銷毀
• 主線程的RunLoop已經(jīng)自動(dòng)獲染跬础（創(chuàng)建）役衡，子線程默認(rèn)沒有開啟RunLoop

3、獲取RunLoop對(duì)象

• Foundation

[NSRunLoop currentRunLoop]; // 獲得當(dāng)前線程的RunLoop對(duì)象
[NSRunLoop mainRunLoop]; // 獲得主線程的RunLoop對(duì)象

• Core Foundation

CFRunLoopGetCurrent(); // 獲得當(dāng)前線程的RunLoop對(duì)象
CFRunLoopGetMain(); // 獲得主線程的RunLoop對(duì)象

4薪棒、RunLoop相關(guān)的類

Core Foundation中關(guān)于RunLoop的5個(gè)類

• CFRunLoopRef
• CFRunLoopModeRef
• CFRunLoopSourceRef
• CFRunLoopTimerRef
• CFRunLoopObserverRef

typedef struct __CFRunLoop * CFRunLoopRef;
struct __CFRunLoop {
    CFRuntimeBase _base;
    pthread_mutex_t _lock;          /* locked for accessing mode list */
    __CFPort _wakeUpPort;           // used for CFRunLoopWakeUp 
    Boolean _unused;
    volatile _per_run_data *_perRunData;              // reset for runs of the run loop
    pthread_t _pthread;
    uint32_t _winthread;
    CFMutableSetRef _commonModes;
    CFMutableSetRef _commonModeItems;
    CFRunLoopModeRef _currentMode;
    CFMutableSetRef _modes;
    struct _block_item *_blocks_head;
    struct _block_item *_blocks_tail;
    CFAbsoluteTime _runTime;
    CFAbsoluteTime _sleepTime;
    CFTypeRef _counterpart;
};

typedef struct __CFRunLoopMode *CFRunLoopModeRef;

struct __CFRunLoopMode {
    CFRuntimeBase _base;
    pthread_mutex_t _lock;  /* must have the run loop locked before locking this */
    CFStringRef _name;
    Boolean _stopped;
    char _padding[3];
    CFMutableSetRef _sources0;
    CFMutableSetRef _sources1;
    CFMutableArrayRef _observers;
    CFMutableArrayRef _timers;
    CFMutableDictionaryRef _portToV1SourceMap;
    __CFPortSet _portSet;
    CFIndex _observerMask;
#if USE_DISPATCH_SOURCE_FOR_TIMERS
    dispatch_source_t _timerSource;
    dispatch_queue_t _queue;
    Boolean _timerFired; // set to true by the source when a timer has fired
    Boolean _dispatchTimerArmed;
#endif
#if USE_MK_TIMER_TOO
    mach_port_t _timerPort;
    Boolean _mkTimerArmed;
#endif
#if DEPLOYMENT_TARGET_WINDOWS
    DWORD _msgQMask;
    void (*_msgPump)(void);
#endif
    uint64_t _timerSoftDeadline; /* TSR */
    uint64_t _timerHardDeadline; /* TSR */
};

Runloop結(jié)構(gòu).jpg

4.1 CFRunLoopModeRef

• CFRunLoopModeRef代表RunLoop的運(yùn)行模式
• 一個(gè)RunLoop包含若干個(gè)Mode手蝎，每個(gè)Mode又包含若干個(gè)Source0/Source1/Timer/Observer
• RunLoop啟動(dòng)時(shí)只能選擇其中一個(gè)Mode，作為currentMode
• 如果需要切換Mode俐芯，只能退出當(dāng)前Loop柑船，再重新選擇一個(gè)Mode進(jìn)入
• 不同組的Source0/Source1/Timer/Observer能分隔開來，互不影響
• 如果Mode里沒有任何Source0/Source1/Timer泼各，RunLoop會(huì)立馬退出

RunloopMode.jpg

iOS 常用3種Mode

• kCFRunLoopDefaultMode：App的默認(rèn)Mode，通常主線程是在這個(gè)Mode下運(yùn)行
• UITrackingRunLoopMode：界面跟蹤 Mode亏拉，用于 ScrollView 追蹤觸摸滑動(dòng)扣蜻，保證界面滑動(dòng)時(shí)不受其他 Mode 影響
• kCFRunLoopCommonModes：這是一個(gè)占位用的Mode，不是一種真正的Mode

4.2 CFRunLoopObserverRef

typedef CF_OPTIONS(CFOptionFlags, CFRunLoopActivity) {
    kCFRunLoopEntry = (1UL << 0),            //即將進(jìn)入Loop
    kCFRunLoopBeforeTimers = (1UL << 1), //即將處理Time
    kCFRunLoopBeforeSources = (1UL << 2),//即將處理Source
    kCFRunLoopBeforeWaiting = (1UL << 5),//即將進(jìn)入休眠
    kCFRunLoopAfterWaiting = (1UL << 6), //剛從休眠中喚醒
    kCFRunLoopExit = (1UL << 7),             //即將退出Loop
    kCFRunLoopAllActivities = 0x0FFFFFFFU
};

添加Observer監(jiān)聽RunLoop的所有狀態(tài)

- (void)addRunloopObserver {
    CFRunLoopObserverRef observer = CFRunLoopObserverCreateWithHandler(kCFAllocatorDefault, kCFRunLoopAllActivities, YES, 0, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
        switch (activity) {
            case kCFRunLoopEntry: {
                CFRunLoopMode mode = CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent());
                NSLog(@"kCFRunLoopEntry - %@", mode);
                CFRelease(mode);
            }
                break;
            case kCFRunLoopBeforeTimers:
                NSLog(@"kCFRunLoopBeforeTimers");
                break;
            case kCFRunLoopBeforeSources:
                NSLog(@"kCFRunLoopBeforeSources");
                break;
            case kCFRunLoopBeforeWaiting:
                NSLog(@"kCFRunLoopBeforeWaiting");
                break;
            case kCFRunLoopAfterWaiting:
                NSLog(@"kCFRunLoopAfterWaiting");
                break;
            case kCFRunLoopExit: {
                CFRunLoopMode mode = CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent());
                NSLog(@"kCFRunLoopExit - %@", mode);
                CFRelease(mode);
            }
                break;
            default:
                break;
        }
    });
    CFRunLoopAddObserver(CFRunLoopGetCurrent(), observer, kCFRunLoopCommonModes);
    CFRelease(observer);
}

5及塘、RunLoop的運(yùn)行邏輯

RunLoop的運(yùn)行邏輯

• Source0: 觸摸事件處理莽使、performSelector:onThread:
• Source1: 基于Port的線程間通信、系統(tǒng)事件捕捉
• Timers: NSTimer笙僚、performSelector:withObject:afterDelay:
• Observers: 用于監(jiān)聽RunLoop的狀態(tài)芳肌、UI刷新（BeforeWaiting)、Autorelease pool（BeforeWaiting）

Runloop運(yùn)行流程.jpg

6肋层、RunLoop休眠的實(shí)現(xiàn)原理

Runloop休眠原理.jpg

7亿笤、RunLoop應(yīng)用

• 控制線程生命周期（線程保活）
• 解決NSTimer在滑動(dòng)時(shí)停止工作的問題 (NSRunLoopCommonModes)
• 監(jiān)控應(yīng)用卡頓
• 性能優(yōu)化

線程倍安活

@interface SRThread : NSThread

@end

@implementation SRThread
- (void)dealloc {
    NSLog(@"%s", __func__);
}
@end

@interface ViewController ()
@property (strong, nonatomic) SRThread *thread;
@property (assign, nonatomic, getter=isStoped) BOOL stopped;
@end

@implementation ViewController

- (void)dealloc {
    NSLog(@"%s", __func__);
    [self stop];
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
    __weak typeof(self) weakSelf = self;
    
    self.stopped = NO;
    self.thread = [[SRThread alloc] initWithBlock:^{
        NSLog(@"%@----begin----", [NSThread currentThread]);
        
        // 往RunLoop里面添加Source\Timer
        [[NSRunLoop currentRunLoop] addPort:[[NSPort alloc] init] forMode:NSDefaultRunLoopMode];
        
        while (weakSelf && !weakSelf.isStoped) {
            [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
        }
        
        NSLog(@"%@----end----", [NSThread currentThread]);
    }];
    [self.thread start];
    self.view.backgroundColor = [UIColor greenColor];
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    if (!self.thread) {
        return;
    }
    
    [self performSelector:@selector(test) onThread:self.thread withObject:nil waitUntilDone:NO];
}

// 子線程需要執(zhí)行的任務(wù)
- (void)test {
    NSLog(@"%s %@", __func__, [NSThread currentThread]);
}

- (void)stop {
    if (!self.thread) {
        return;
    }
    
    // 在子線程調(diào)用stop（waitUntilDone設(shè)置為YES净薛，代表子線程的代碼執(zhí)行完畢后，這個(gè)方法才會(huì)往下走）
    [self performSelector:@selector(stopThread) onThread:self.thread withObject:nil waitUntilDone:YES];
}

// 用于停止子線程的RunLoop
- (void)stopThread {
    // 設(shè)置標(biāo)記為YES
    self.stopped = YES;
    
    // 停止RunLoop
    CFRunLoopStop(CFRunLoopGetCurrent());
    NSLog(@"%s %@", __func__, [NSThread currentThread]);
    
    // 清空線程
    self.thread = nil;
}

@end

持久線程封裝

#import <Foundation/Foundation.h>

/**
 該線程執(zhí)行完任務(wù)不會(huì)銷毀蒲拉， 手動(dòng)調(diào)用stop后肃拜，線程銷毀了
 */
@interface SRPermenantThread : NSObject
/**
 在當(dāng)前子線程執(zhí)行一個(gè)任務(wù)
 */
- (void)executeTask:(dispatch_block_t)task;

/**
 結(jié)束線程
 */
- (void)stop;

@end

@interface SRPermenantThread()
@property (strong, nonatomic) NSThread *innerThread;
@end

@implementation SRPermenantThread

- (void)dealloc {
    [self stop];
}

#pragma mark - public methods

- (instancetype)init {
    if (self = [super init]) {
        self.innerThread = [[NSThread alloc] initWithBlock:^{
            // 創(chuàng)建上下文（要初始化一下結(jié)構(gòu)體）
            CFRunLoopSourceContext context = {0};
            
            // 創(chuàng)建source
            CFRunLoopSourceRef source = CFRunLoopSourceCreate(kCFAllocatorDefault, 0, &context);
            
            // 往Runloop中添加source
            CFRunLoopAddSource(CFRunLoopGetCurrent(), source, kCFRunLoopDefaultMode);
            
            // 銷毀source
            CFRelease(source);
            
            // 啟動(dòng)
            CFRunLoopRunInMode(kCFRunLoopDefaultMode, 1.0e10, false);
        }];
        
        [self.innerThread start];
    }
    return self;
}

- (void)executeTask:(dispatch_block_t)task {
    if (!self.innerThread || !task) return;
    
    [self performSelector:@selector(__executeTask:) onThread:self.innerThread withObject:task waitUntilDone:NO];
}

- (void)stop {
    if (!self.innerThread) {
        return;
    }
    
    [self performSelector:@selector(__stop) onThread:self.innerThread withObject:nil waitUntilDone:YES];
}


#pragma mark - private methods

- (void)__stop {
    CFRunLoopStop(CFRunLoopGetCurrent());
    self.innerThread = nil;
}

- (void)__executeTask:(dispatch_block_t)task {
    task();
}

@end