什么是RunLoop?
顧名思義：運行循環(huán)丧枪，在程序運行過程中循環(huán)做一些事情
應(yīng)用范疇：
·定時器（Timer）、PerformSelector
·GCD Async Main Queue
·事件響應(yīng)葵陵、手勢識別稚新、界面刷新
·網(wǎng)絡(luò)請求
·AutoreleasePool
RunLoop與線程
·每條線程都有唯一的一個與之對應(yīng)的RunLoop對象
·RunLoop保存在一個全局的Dictionary里既绩，線程作為key世曾，RunLoop作為value
·線程剛創(chuàng)建時并沒有RunLoop對象，RunLoop會在第一次獲取它時創(chuàng)建
·RunLoop會在線程結(jié)束時銷毀
·主線程的RunLoop已經(jīng)自動獲扰住（創(chuàng)建）搓逾，子線程默認沒有開啟RunLoop
獲取RunLoop對象
Foundation
[NSRunLoop currentRunLoop]; // 獲得當前線程的RunLoop對象
[NSRunLoop mainRunLoop]; // 獲得主線程的RunLoop對象
Core Foundation
CFRunLoopGetCurrent(); // 獲得當前線程的RunLoop對象
CFRunLoopGetMain(); // 獲得主線程的RunLoop對象
RunLoop相關(guān)的類
Core Foundation中關(guān)于RunLoop的5個類
- CFRunLoopRef
- CFRunLoopModeRef
- CFRunLoopSourceRef
- CFRunLoopTimerRef
- CFRunLoopObserverRef
RunLoop底層數(shù)據(jù)結(jié)構(gòu)
RunLoop底層結(jié)構(gòu).png
CFRunLoopModeRef
CFRunLoopModeRef代表RunLoop的運行模式
一個RunLoop包含若干個Mode，每個Mode又包含若干個Source0/Source1/Timer/Observer
RunLoop啟動時只能選擇其中一個Mode杯拐，作為currentMode
如果需要切換Mode霞篡，只能退出當前Loop，再重新選擇一個Mode進入
·不同組的Source0/Source1/Timer/Observer能分隔開來端逼，互不影響如果Mode里沒有任何Source0/Source1/Timer/Observer朗兵，RunLoop會立馬退出
常見的2種Mode
- kCFRunLoopDefaultMode（NSDefaultRunLoopMode）：App的默認Mode，通常主線程是在這個Mode下運行
- UITrackingRunLoopMode：界面跟蹤 Mode顶滩，用于 ScrollView 追蹤觸摸滑動余掖，保證界面滑動時不受其他 Mode 影響
CFRunLoopObserverRef
/* Run Loop Observer Activities */
typedef CF_OPTIONS(CFOptionFlags, CFRunLoopActivity) {
kCFRunLoopEntry = (1UL << 0), //即將進入Loop
kCFRunLoopBeforeTimers = (1UL << 1), //即將處理Timer
kCFRunLoopBeforeSources = (1UL << 2), //即將處理Source
kCFRunLoopBeforeWaiting = (1UL << 5), //即將進入休眠
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)
// 創(chuàng)建Observer
CFRunLoopObserverRef observer = CFRunLoopObserverCreateWithHandler(kCFAllocatorDefault, kCFRunLoopAllActivities, YES, 0, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
switch (activity) {
case kCFRunLoopEntry:
NSLog(@"kCFRunLoopEntry");
break;
case kCFRunLoopBeforeTimers:
NSLog(@"kCFRunLoopBeforeTimers");
break;
case kCFRunLoopBeforeSources:
NSLog(@"kCFRunLoopBeforeSources");
break;
case kCFRunLoopBeforeWaiting:
NSLog(@"kCFRunLoopBeforeWaiting");
break;
case kCFRunLoopAfterWaiting:
NSLog(@"kCFRunLoopAfterWaiting");
break;
case kCFRunLoopExit:
NSLog(@"kCFRunLoopExit");
break;
default:
break;
}
});
// 添加Observer到RunLoop中
CFRunLoopAddObserver(CFRunLoopGetCurrent(), observer, kCFRunLoopCommonModes);
// 釋放
CFRelease(observer);
RunLoop的運行邏輯
底層源碼的主要邏輯
// RunLoop入口
SInt32 CFRunLoopRunSpecific(CFRunLoopRef rl, CFStringRef modeName, CFTimeInterval seconds, Boolean returnAfterSourceHandled) { /* DOES CALLOUT */
int32_t result = kCFRunLoopRunFinished;
// 通知Observers: 進入Loop
if (currentMode->_observerMask & kCFRunLoopEntry ) __CFRunLoopDoObservers(rl, currentMode, kCFRunLoopEntry);
// 具體要做的事情
result = __CFRunLoopRun(rl, currentMode, seconds, returnAfterSourceHandled, previousMode);
// 通知Observers: 退出Loop
if (currentMode->_observerMask & kCFRunLoopExit ) __CFRunLoopDoObservers(rl, currentMode, kCFRunLoopExit);
return result;
}
// RunLoop主要邏輯
static int32_t __CFRunLoopRun(CFRunLoopRef rl, CFRunLoopModeRef rlm, CFTimeInterval seconds, Boolean stopAfterHandle, CFRunLoopModeRef previousMode) {
uint64_t startTSR = mach_absolute_time();
do {
// 通知Observer：即將處理Timers
if (rlm->_observerMask & kCFRunLoopBeforeTimers) __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeTimers);
// 通知Observer：即將處理Sources
if (rlm->_observerMask & kCFRunLoopBeforeSources) __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeSources);
// 處理Blocks
__CFRunLoopDoBlocks(rl, rlm);
// 處理Source0
Boolean sourceHandledThisLoop = __CFRunLoopDoSources0(rl, rlm, stopAfterHandle);
if (sourceHandledThisLoop) {
// 處理Blocks
__CFRunLoopDoBlocks(rl, rlm);
}
// 判斷有無Source1
if (__CFRunLoopServiceMachPort(dispatchPort, &msg, sizeof(msg_buffer), &livePort, 0, &voucherState, NULL)) {
// 如果有Source1,就跳轉(zhuǎn)到handel_msg
goto handle_msg;
}
// 通知Observers：即將休眠
if (!poll && (rlm->_observerMask & kCFRunLoopBeforeWaiting)) __CFRunLoopDoObservers(rl, rlm, kCFRunLoopBeforeWaiting);
__CFRunLoopSetSleeping(rl);
// 等待別的消息來喚醒當前線程
__CFRunLoopServiceMachPort(waitSet, &msg, sizeof(msg_buffer), &livePort, poll ? 0 : TIMEOUT_INFINITY, &voucherState, &voucherCopy);
// 通知Observer：結(jié)束休眠
__CFRunLoopUnsetSleeping(rl);
if (!poll && (rlm->_observerMask & kCFRunLoopAfterWaiting)) __CFRunLoopDoObservers(rl, rlm, kCFRunLoopAfterWaiting);
handle_msg:;
__CFRunLoopSetIgnoreWakeUps(rl);
if (rlm->_timerPort != MACH_PORT_NULL && livePort == rlm->_timerPort) {
// 被Timer喚醒了
CFRUNLOOP_WAKEUP_FOR_TIMER();
// 處理Timers
if (!__CFRunLoopDoTimers(rl, rlm, mach_absolute_time())) {
// Re-arm the next timer
__CFArmNextTimerInMode(rlm, rl);
}
} else if (livePort == dispatchPort) {
// 被GCD喚醒
CFRUNLOOP_WAKEUP_FOR_DISPATCH();
// 處理GCD
__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__(msg);
} else {
//被Source1喚醒
CFRUNLOOP_WAKEUP_FOR_SOURCE();
// 處理Source1
sourceHandledThisLoop = __CFRunLoopDoSource1(rl, rlm, rls, msg, msg->msgh_size, &reply) || sourceHandledThisLoop;
}
// 處理Blocks
__CFRunLoopDoBlocks(rl, rlm);
//設(shè)置返回值
if (sourceHandledThisLoop && stopAfterHandle) {
retVal = kCFRunLoopRunHandledSource;
} else if (timeout_context->termTSR < mach_absolute_time()) {
retVal = kCFRunLoopRunTimedOut;
} else if (__CFRunLoopIsStopped(rl)) {
__CFRunLoopUnsetStopped(rl);
retVal = kCFRunLoopRunStopped;
} else if (rlm->_stopped) {
rlm->_stopped = false;
retVal = kCFRunLoopRunStopped;
} else if (__CFRunLoopModeIsEmpty(rl, rlm, previousMode)) {
retVal = kCFRunLoopRunFinished;
}
} while (0 == retVal);
return retVal;
}
RunLoop在實際中的應(yīng)用
- 解決NSTimer在滑動時停止工作的問題
問題：頁面滑動時，RunLoop會切換到UITrackingRunLoopMode礁鲁，timer會停止盐欺。
解決辦法：
將timer 添加到當前RunLoop，使用CommonModes
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes]
注意：
NSDefaultRunLoopMode仅醇、UITrackingRunLoopMode才是真正的存在模式
NSRunLoopCommonModes并不是一個真的模式冗美，它只是一個標記
timer能在_commonModes數(shù)組中存在的模式下工作
- 控制線程生命周期（線程保活）
AFNetworking就是創(chuàng)建了子線程析二，然后讓子線程一直存在于后臺粉洼，方便進行一些子線程的任務(wù)，減少線程創(chuàng)建銷毀的開銷叶摄，提高性能
@interface ViewController ()
@property (strong, nonatomic) NSThread *thread;
@property (assign, nonatomic, getter=isStoped) BOOL stopped;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
__weak typeof(self) weakSelf = self;
self.stopped = NO;
self.thread = [[NSThread alloc] initWithBlock:^{
NSLog(@"%@----begin----", [NSThread currentThread]);
// 往RunLoop里面添加Source\Timer\Observer
[[NSRunLoop currentRunLoop] addPort:[[NSPort alloc] init] forMode:NSDefaultRunLoopMode];
while (weakSelf && !weakSelf.isStoped) {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
/*
it runs the receiver in the NSDefaultRunLoopMode by repeatedly invoking runMode:beforeDate:.
In other words, this method effectively begins an infinite loop that processes data from the run loop’s input sources and timers
*/
// [[NSRunLoop currentRunLoop] run];
// NSRunLoop的run方法是無法停止的属韧，它專門用于開啟一個永不銷毀的線程（NSRunLoop）
NSLog(@"%@----end----", [NSThread currentThread]);
}];
[self.thread start];
}
- (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，代表子線程的代碼執(zhí)行完畢后蛤吓，這個方法才會往下走）
[self performSelector:@selector(stopThread) onThread:self.thread withObject:nil waitUntilDone:YES];
}
// 用于停止子線程的RunLoop
- (void)stopThread
{
// 設(shè)置標記為YES
self.stopped = YES;
// 停止RunLoop
CFRunLoopStop(CFRunLoopGetCurrent());
NSLog(@"%s %@", __func__, [NSThread currentThread]);
// 清空線程
self.thread = nil;
}
- (void)dealloc
{
NSLog(@"%s", __func__);
[self stop];
}
- 監(jiān)控應(yīng)用卡頓
- 性能優(yōu)化
面試題
1.runloop的內(nèi)部實用邏輯宵喂？
RunLoop的運行邏輯圖.png
2.runloop是怎么響應(yīng)用戶的操作的，具體流程是怎么樣的柱衔？
以屏幕點擊為例樊破， Source1捕捉系統(tǒng)事件愉棱，將事件包裝成事件隊列（EventQueue）唆铐，事件隊列是在Source0中處理的（Source1捕捉哲戚，Source0處理）
