以下关于RunLoop的资料都比较好：
RunLoop充满灵性的死循环：http://www.jianshu.com/p/b9426458fcf6
视频——iOS线下分享RunLoop（孙源）：http://v.youku.com/v_show/id_XODgxODkzODI0.html
非常好的博文Runloop：https://www.zybuluo.com/qidiandasheng/note/346387
-
NSTimer需要注意的地方：https://www.zybuluo.com/qidiandasheng/note/492821
- 问题：如果我就是想让这个 NSTimer 一直输出，直到 DemoViewController 销毁了才停止，我该如何让它停止呢？ http://www.cocoachina.com/ios/20150710/12444.html
- Demo示例：https://github.com/ChatGame/HWWeakTimer
RunLoop 入门 看我就够了:http://ios.jobbole.com/92177/
【iOS程序启动与运转】- RunLoop个人小结 http://www.jianshu.com/p/37ab0397fec7#
深入理解RunLoop[http://blog.ibireme.com/2015/05/18/runloop/]
RunLoop使用场景
一、保证线程长时间存活
- 问题描述：不希望一些花费时间较长的操作阻塞主线程而导致界面卡顿，就需要创建一个子线程，然后把该操作放在子线程中来处理。可是当子线程中的任务执行完毕后，子线程就会被销毁掉。
@interface YTThread : NSThread
@end
@implementation YTThread
- (void)dealloc {
NSLog(@"%s",__func__);
}
@end
- (void)viewDidLoad {
[super viewDidLoad];
self.title = @"RunLoop";
[self threadTest];
}
- (void)threadTest {
YTThread *thread = [[YTThread alloc] initWithTarget:self selector:@selector(subThreadOpetion) object:nil];
[thread start];
}
- (void)subThreadOpetion {
@autoreleasepool {
NSLog(@"%@----子线程任务开始",[NSThread currentThread]);
[NSThread sleepForTimeInterval:3.0];
NSLog(@"%@----子线程任务结束",[NSThread currentThread]);
}
}
2017-05-27 11:05:05.444 MXBarManagerDemo[23405:2814835] <YTThread: 0x600000268300>{number = 3, name = (null)}----子线程任务开始
2017-05-27 11:05:08.450 MXBarManagerDemo[23405:2814835] <YTThread: 0x600000268300>{number = 3, name = (null)}----子线程任务结束
2017-05-27 11:05:08.450 MXBarManagerDemo[23405:2814835] -[YTThread dealloc]
- 当子线程中任务执行完后线程被立刻销毁。如果程序中需要经常在子线程中执行任务，频繁的创建和销毁线程会造成资源的浪费。这时可以使用RunLoop来让该线程长时间存活而不被销毁。如下所示：
@interface TestRunLoopViewController ()
@property (nonatomic, strong) NSThread *subThread;
@end
@implementation TestRunLoopViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.title = @"RunLoop";
[self threadTest];
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
[self performSelector:@selector(subThreadOpetion) onThread:self.subThread withObject:nil waitUntilDone:NO];
}
- (void)threadTest {
YTThread *thread = [[YTThread alloc] initWithTarget:self selector:@selector(subThreadEntryPoint) object:nil];
[thread setName:@"YTThread"];
[thread start];
self.subThread = thread;
}
- (void)subThreadEntryPoint {
@autoreleasepool {
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop addPort:[NSMachPort port] forMode:NSDefaultRunLoopMode];
// NSLog(@"runLoop--%@", runLoop);
NSLog(@"启动RunLoop前--%@",runLoop.currentMode);
[runLoop run];
}
}
- (void)subThreadOpetion {
@autoreleasepool {
NSLog(@"%@----子线程任务开始",[NSThread currentThread]);
[NSThread sleepForTimeInterval:3.0];
NSLog(@"%@----子线程任务结束",[NSThread currentThread]);
}
}
@end
2017-05-27 11:17:26.064 MXBarManagerDemo[23458:2865125] 启动RunLoop前--(null)
2017-05-27 11:17:30.627 MXBarManagerDemo[23458:2865125] <YTThread: 0x600000269640>{number = 3, name = YTThread}----子线程任务开始
2017-05-27 11:17:33.632 MXBarManagerDemo[23458:2865125] <YTThread: 0x600000269640>{number = 3, name = YTThread}----子线程任务结束
2017-05-27 11:17:36.319 MXBarManagerDemo[23458:2865125] <YTThread: 0x600000269640>{number = 3, name = YTThread}----子线程任务开始
2017-05-27 11:17:39.325 MXBarManagerDemo[23458:2865125] <YTThread: 0x600000269640>{number = 3, name = YTThread}----子线程任务结束
2017-05-27 11:17:56.479 MXBarManagerDemo[23458:2865125] <YTThread: 0x600000269640>{number = 3, name = YTThread}----子线程任务开始
2017-05-27 11:17:59.482 MXBarManagerDemo[23458:2865125] <YTThread: 0x600000269640>{number = 3, name = YTThread}----子线程任务结束
注意几点：
1、获取RunLoop只能使用 [NSRunLoop currentRunLoop] 或 [NSRunLoop mainRunLoop]。
应用程序并不需要自己创建RunLoop，而是要在合适的时间启动runloop。 CF框架源码中有CFRunLoopGetCurrent(void) 和 CFRunLoopGetMain(void),查看源码可知，这两个API中，都是先从全局字典中取。如果没有与该线程对应的RunLoop，那么就会帮我们创建一个RunLoop（创建RunLoop的过程在函数_CFRunLoopGet0(pthread_t t)中）。
2、即使RunLoop开始运行，如果RunLoop 中的 modes 为空，或者要执行的mode里没有item，那么RunLoop会直接在当前loop中返回，并进入睡眠状态。
如注释掉[runLoop addPort:[NSMachPort port] forMode:NSDefaultRunLoopMode];（查看注释前后打印出的runLoop），点击视图，控制台不会有任何输出，因为mode 中并没有item任务。经过NSRunLoop封装后，只可以往mode中添加两类item任务：NSPort（对应的是source）、NSTimer。如果使用CFRunLoopRef,则可以使用C语言API,往mode中添加source、timer、observer。
3、自己创建的Thread中的任务是在kCFRunLoopDefaultMode这个mode中执行的。
查看modes
2017-05-27 14:13:53.475 MXBarManagerDemo[29040:3134640] runLoop--<CFRunLoop 0x610000175180 [0x108d9fe40]>{wakeup port = 0x731b, stopped = false, ignoreWakeUps = true,
current mode = (none),
common modes = <CFBasicHash 0x610000058f00 [0x108d9fe40]>{type = mutable set, count = 1,
entries =>
2 : <CFString 0x108d77970 [0x108d9fe40]>{contents = "kCFRunLoopDefaultMode"}
}
,
common mode items = (null),
modes = <CFBasicHash 0x610000058420 [0x108d9fe40]>{type = mutable set, count = 1,
entries =>
2 : <CFRunLoopMode 0x610000183e90 [0x108d9fe40]>{name = kCFRunLoopDefaultMode, port set = 0x560b, queue = 0x6100001750c0, source = 0x6100001d40a0 (not fired), timer port = 0x7503,
sources0 = <CFBasicHash 0x600000058780 [0x108d9fe40]>{type = mutable set, count = 0,
entries =>
}
,
sources1 = <CFBasicHash 0x60000005abe0 [0x108d9fe40]>{type = mutable set, count = 1,
entries =>
1 : <CFRunLoopSource 0x60000017b480 [0x108d9fe40]>{signalled = No, valid = Yes, order = 200, context = <CFMachPort 0x600000544570 [0x108d9fe40]>{valid = Yes, port = 7603, source = 0x60000017b480, callout = __NSFireMachPort (0x1080a0737), context = <CFMachPort context 0x60000005cdd0>}}
}
,
observers = (null),
timers = (null),
currently 517558433 (51534038374775) / soft deadline in: 1.84466925e+10 sec (@ -1) / hard deadline in: 1.84466925e+10 sec (@ -1)
},
}
}
2017-05-27 14:13:53.476 MXBarManagerDemo[29040:3134640] 启动RunLoop前--(null)
2017-05-27 14:16:58.114 MXBarManagerDemo[29040:3134640] <YTThread: 0x61800007a0c0>{number = 3, name = YTThread}----子线程任务开始
2017-05-27 14:17:01.115 MXBarManagerDemo[29040:3134640] <YTThread: 0x61800007a0c0>{number = 3, name = YTThread}----子线程任务结束
4、在子线程创建好后，最好所有的任务都放在AutoreleasePool中。
- 举例
YYKit中使用YYWebImageOperation对网络图片进行下载请求，使用[self performSelector:@selector(_startRequest:) onThread:[self.class _networkThread] withObject:nil waitUntilDone:NO];将任务丢到后台线程的 RunLoop 中。
// runs on network thread
- (void)_startOperation {
if ([self isCancelled]) return;
@autoreleasepool {
// get image from cache
if (_cache &&
!(_options & YYWebImageOptionUseNSURLCache) &&
!(_options & YYWebImageOptionRefreshImageCache)) {
UIImage *image = [_cache getImageForKey:_cacheKey withType:YYImageCacheTypeMemory];
if (image) {
[_lock lock];
if (![self isCancelled]) {
if (_completion) _completion(image, _request.URL, YYWebImageFromMemoryCache, YYWebImageStageFinished, nil);
}
[self _finish];
[_lock unlock];
return;
}
if (!(_options & YYWebImageOptionIgnoreDiskCache)) {
__weak typeof(self) _self = self;
dispatch_async([self.class _imageQueue], ^{
__strong typeof(_self) self = _self;
if (!self || [self isCancelled]) return;
UIImage *image = [self.cache getImageForKey:self.cacheKey withType:YYImageCacheTypeDisk];
if (image) {
[self.cache setImage:image imageData:nil forKey:self.cacheKey withType:YYImageCacheTypeMemory];
[self performSelector:@selector(_didReceiveImageFromDiskCache:) onThread:[self.class _networkThread] withObject:image waitUntilDone:NO];
} else {
[self performSelector:@selector(_startRequest:) onThread:[self.class _networkThread] withObject:nil waitUntilDone:NO];
}
});
return;
}
}
}
[self performSelector:@selector(_startRequest:) onThread:[self.class _networkThread] withObject:nil waitUntilDone:NO];
}
/// Network thread entry point.
+ (void)_networkThreadMain:(id)object {
@autoreleasepool {
[[NSThread currentThread] setName:@"com.ibireme.yykit.webimage.request"];
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop addPort:[NSMachPort port] forMode:NSDefaultRunLoopMode];
[runLoop run];
}
}
/// Global image request network thread, used by NSURLConnection delegate.
+ (NSThread *)_networkThread {
static NSThread *thread = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
thread = [[NSThread alloc] initWithTarget:self selector:@selector(_networkThreadMain:) object:nil];
if ([thread respondsToSelector:@selector(setQualityOfService:)]) {
thread.qualityOfService = NSQualityOfServiceBackground;
}
[thread start];
});
return thread;
}
二、RunLoop如何保证NSTimer在视图滑动时依然能正常运转
问题描述：UITableView的header 上是一个横向ScrollView，使用NSTimer每隔几秒切换一张图片,当滑动UITableView的时顶部的scollView并不会切换图片;UITableView有显示倒计时的Label，当滑动tableView时倒计时就停止了。
-
创建定时器的两种方法
方法1和方法2等价，区别：方法2默认也是将timer添加到NSDefaultRunLoopMode下的，并且会自动fire。
- (void)viewDidLoad {
[super viewDidLoad];
// 方法1
NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(timerUpdate) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
[timer fire];
// 方法2
// [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerUpdate) userInfo:nil repeats:YES];
}
- (void)timerUpdate {
NSLog(@"当前线程：%@",[NSThread currentThread]);
NSLog(@"启动RunLoop后--%@",[NSRunLoop currentRunLoop].currentMode);
// NSLog(@"currentRunLoop:%@",[NSRunLoop currentRunLoop]);
dispatch_async(dispatch_get_main_queue(), ^{
self.count ++;
NSString *timerText = [NSString stringWithFormat:@"计时器:%ld",self.count];
self.timerLabel.text = timerText;
});
}
2017-05-27 17:21:55.418 MXBarManagerDemo[32985:3929954] 当前线程：<NSThread: 0x600000066140>{number = 1, name = main}
2017-05-27 17:21:55.419 MXBarManagerDemo[32985:3929954] 启动RunLoop后--kCFRunLoopDefaultMode
原因：滑动scrollView时主线程的RunLoop 会切换到UITrackingRunLoopMode这个Mode，执行的也是UITrackingRunLoopMode下的任务（Mode中的item），而timer 是添加在NSDefaultRunLoopMode下的，所以timer任务并不会执行。只有当UITrackingRunLoopMode的任务执行完毕，RunLoop切换到NSDefaultRunLoopMode后，才会继续执行timer。
解决方法：需要在添加timer 时，将mode 设置为NSRunLoopCommonModes即可，只针对方法1。方法2因为是固定添加到defaultMode中，就不要用了。
关于timer的坑
上面的示例是在主线程中使用timer。在子线程中使用timer也可解决上面的问题，但需注意的是把timer加入到当前runloop后，必须让runloop 运行起来，否则timer仅执行一次。
- (void)viewDidLoad {
[super viewDidLoad];
......
[self createThread];
}
- (void)createThread {
NSThread *subThread = [[NSThread alloc] initWithTarget:self selector:@selector(timerTest) object:nil];
[subThread start];
self.subThread = subThread;
}
- (void)timerTest {
@autoreleasepool {
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
NSLog(@"启动RunLoop前--%@",runLoop.currentMode);
NSLog(@"currentRunLoop:%@",[NSRunLoop currentRunLoop]);
// 方法1
// NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(timerUpdate) userInfo:nil repeats:YES];
// [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
// [timer fire];
// 方法2
[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerUpdate) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] run];
}
}
- (void)timerUpdate {
NSLog(@"当前线程：%@",[NSThread currentThread]);
NSLog(@"启动RunLoop后--%@",[NSRunLoop currentRunLoop].currentMode);
// NSLog(@"currentRunLoop:%@",[NSRunLoop currentRunLoop]);
dispatch_async(dispatch_get_main_queue(), ^{
self.count ++;
NSString *timerText = [NSString stringWithFormat:@"计时器:%ld",self.count];
self.timerLabel.text = timerText;
});
}
添加timer 前的控制台输出:
2017-05-27 22:31:41.162 MXBarManagerDemo[704:80646] 启动RunLoop前--(null)
2017-05-27 22:31:41.163 MXBarManagerDemo[704:80646] currentRunLoop:<CFRunLoop 0x60000016b340 [0x10d83ce40]>{wakeup port = 0x741b, stopped = false, ignoreWakeUps = true,
current mode = (none),
common modes = <CFBasicHash 0x600000240450 [0x10d83ce40]>{type = mutable set, count = 1,
entries =>
2 : <CFString 0x10d814970 [0x10d83ce40]>{contents = "kCFRunLoopDefaultMode"}
}
,
common mode items = (null),
modes = <CFBasicHash 0x600000242ca0 [0x10d83ce40]>{type = mutable set, count = 1,
entries =>
2 : <CFRunLoopMode 0x600000199570 [0x10d83ce40]>{name = kCFRunLoopDefaultMode, port set = 0x560b, queue = 0x600000168ac0, source = 0x6000001d8600 (not fired), timer port = 0x7603,
sources0 = (null),
sources1 = (null),
observers = (null),
timers = (null),
currently 517588301 (785273542974) / soft deadline in: 1.84467433e+10 sec (@ -1) / hard deadline in: 1.84467433e+10 sec (@ -1)
},
}
}
添加timer后的控制台输出：
2017-05-27 22:32:33.924 MXBarManagerDemo[704:80646] 当前线程：<NSThread: 0x61000006e180>{number = 3, name = (null)}
2017-05-27 22:32:33.924 MXBarManagerDemo[704:80646] 启动RunLoop后--kCFRunLoopDefaultMode
2017-05-27 22:32:33.927 MXBarManagerDemo[704:80646] currentRunLoop:<CFRunLoop 0x60000016b340 [0x10d83ce40]>{wakeup port = 0x741b, stopped = false, ignoreWakeUps = true,
current mode = kCFRunLoopDefaultMode,
common modes = <CFBasicHash 0x600000240450 [0x10d83ce40]>{type = mutable set, count = 1,
entries =>
2 : <CFString 0x10d814970 [0x10d83ce40]>{contents = "kCFRunLoopDefaultMode"}
}
,
common mode items = (null),
modes = <CFBasicHash 0x600000242ca0 [0x10d83ce40]>{type = mutable set, count = 1,
entries =>
2 : <CFRunLoopMode 0x600000199570 [0x10d83ce40]>{name = kCFRunLoopDefaultMode, port set = 0x560b, queue = 0x600000168ac0, source = 0x6000001d8600 (not fired), timer port = 0x7603,
sources0 = (null),
sources1 = (null),
observers = (null),
timers = <CFArray 0x6180000bda60 [0x10d83ce40]>{type = mutable-small, count = 1, values = (
0 : <CFRunLoopTimer 0x618000169000 [0x10d83ce40]>{valid = Yes, firing = Yes, interval = 5, tolerance = 0, next fire date = 517588354 (-0.00657904148 @ 838031380701), callout = (NSTimer) [TestRunLoopViewController timerUpdate] (0x10cb44ec4 / 0x10ca00960) (/Users/yitudev/Library/Developer/CoreSimulator/Devices/CA10957A-B14D-4E49-80EE-E2B23C4E6183/data/Containers/Bundle/Application/8809F8A7-130A-4AC5-B9D6-798FFB53C6B1/MXBarManagerDemo.app/MXBarManagerDemo), context = <CFRunLoopTimer context 0x618000024880>}
)},
currently 517588354 (838035515992) / soft deadline in: 1.84467432e+10 sec (@ -1) / hard deadline in: 1.84467432e+10 sec (@ -1)
},
}
}
- 从控制台输出可以看出，timer确实被添加到NSDefaultRunLoopMode中了。可是添加到子线程中的NSDefaultRunLoopMode里，无论如何滚动，timer都能够很正常的运转。
解释：多线程与runloop的关系 —— 每一个线程都有一个与之关联的RunLoop，而每一个RunLoop可能会有多个Mode。CPU会在多个线程间切换来执行任务，呈现出多个线程同时执行的效果。执行的任务其实就是RunLoop去各个Mode里执行各个item。因为RunLoop是独立的两个，相互不会影响，所以在子线程添加timer，滑动视图时，timer能正常运行。
- 结论
1、如果是在主线程中运行timer，想要timer在某界面有视图滚动时依然能正常运转，那么将timer添加到RunLoop中时，就需要设置mode 为NSRunLoopCommonModes。
2、如果是在子线程中运行timer，那么将timer添加到RunLoop中后，Mode设置为NSDefaultRunLoopMode或NSRunLoopCommonModes均可，但是需要保证RunLoop在运行，且其中有任务。
三、RunLoop如何保证不影响UI卡顿
- 问题描述：UITableView、UICollectionView等延迟加载图片。
以UITableView 的 cell 上显示网络图片为例，需要两步：1、下载网络图片；2、将网络图片设置到UIImageView上。为了不影响滑动第1步一般都是放在子线程处理，第2步回到主线程设置。model切换调用方法performSelector:withObject:afterDelay:inModes:，如下（方法2）：
UIImage *downloadedImage = ....;
// 方法1
// self.myImageView.image = downloadedImage;
// 方法2
[self.myImageView performSelector:@selector(setImage:) withObject:downloadedImage afterDelay:0 inModes:@[NSDefaultRunLoopMode]];
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *identifier = @"cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier];
}
for (NSInteger i = 1; i <= 5; i++) {
[[cell.contentView viewWithTag:i] removeFromSuperview];
}
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(5, 5, 300, 25)];
label.backgroundColor = [UIColor clearColor];
label.textColor = [UIColor redColor];
label.text = [NSString stringWithFormat:@"%zd - Drawing index is top priority", indexPath.row];
label.font = [UIFont boldSystemFontOfSize:13];
label.tag = 1;
[cell.contentView addSubview:label];
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(105, 20, 85, 85)];
imageView.tag = 2;
NSString *path = [[NSBundle mainBundle] pathForResource:@"timg" ofType:@"jpeg"];
UIImage *image = [UIImage imageWithContentsOfFile:path];
imageView.contentMode = UIViewContentModeScaleAspectFit;
imageView.image = image; // 方法1设置图片
// [imageView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:NO modes:@[NSDefaultRunLoopMode]]; // 方法2设置图片
NSLog(@"current:%@", [NSRunLoop currentRunLoop].currentMode);
[cell.contentView addSubview:imageView];
UIImageView *imageView2 = [[UIImageView alloc] initWithFrame:CGRectMake(200, 20, 85, 85)];
imageView2.tag = 3;
UIImage *image2 = [UIImage imageWithContentsOfFile:path];
imageView2.contentMode = UIViewContentModeScaleAspectFit;
imageView2.image = image2;
// [imageView2 performSelectorOnMainThread:@selector(setImage:) withObject:image2 waitUntilDone:NO modes:@[NSDefaultRunLoopMode]];
[cell.contentView addSubview:imageView2];
UILabel *label2 = [[UILabel alloc] initWithFrame:CGRectMake(5, 99, 300, 35)];
label2.lineBreakMode = NSLineBreakByWordWrapping;
label2.numberOfLines = 0;
label2.backgroundColor = [UIColor clearColor];
label2.textColor = [UIColor colorWithRed:0 green:100.f / 255.f blue:0 alpha:1];
label2.text = [NSString stringWithFormat:@"%zd - Drawing large image is low priority. Should be distributed into different run loop passes.", indexPath.row];
label2.font = [UIFont boldSystemFontOfSize:13];
label2.tag = 4;
UIImageView *imageView3 = [[UIImageView alloc] initWithFrame:CGRectMake(5, 20, 85, 85)];
imageView3.tag = 5;
UIImage *image3 = [UIImage imageWithContentsOfFile:path];
imageView3.contentMode = UIViewContentModeScaleAspectFit;
imageView3.image = image3;
// [imageView3 performSelectorOnMainThread:@selector(setImage:) withObject:image3 waitUntilDone:NO modes:@[NSDefaultRunLoopMode]];
[cell.contentView addSubview:label2];
[cell.contentView addSubview:imageView3];
return cell;
}
如上所示，一个Cell里有两个Label，和三个imageView,这里的图片是非常高清的。
1、方法1：为imageView设置image,是在UITrackingRunLoopMode中进行的，如果图片很大，图片解压缩和渲染肯定会很耗时，那么卡顿就是必然的。
2、方法2: 切换到NSDefaultRunLoopMode中，一个runloop循环要解压和渲染18张大图（假如一个页面能显示6行，每行3张图），耗时肯定超过50ms(1/60s)。我们可以继续来优化，一次runloop循环，仅渲染一张大图片，分18次来渲染，这样每一次runloop耗时就比较短了，滑动起来就会非常顺畅。这也是 RunLoopWorkDistribution 中的做法，即：首先创建一个单例，单例中定义了几个数组，用来存要在runloop循环中执行的任务，然后为主线程的runloop添加一个CFRunLoopObserver,当主线程在NSDefaultRunLoopMode中执行完任务，即将睡眠前，执行一个单例中保存的一次图片渲染任务。关键代码看 RunLoopWorkDistribution 类即可。
四、使用RunLoop 监测主线程卡顿
问题描述：用RunLoop 监测主线程的卡顿，并将卡顿时的线程堆栈信息保存下来，下次上传到服务器。
-
RunLoop 的内部逻辑:
image 伪代码如下：
{
/// 1. 通知Observers，即将进入RunLoop
/// 此处有Observer会创建AutoreleasePool: _objc_autoreleasePoolPush();
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopEntry);
do {
/// 2. 通知 Observers: 即将触发 Timer 回调。
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopBeforeTimers);
/// 3. 通知 Observers: 即将触发 Source (非基于port的,Source0) 回调。
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopBeforeSources);
__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__(block);
/// 4. 触发 Source0 (非基于port的) 回调。
__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__(source0);
__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__(block);
/// 6. 通知Observers，即将进入休眠
/// 此处有Observer释放并新建AutoreleasePool: _objc_autoreleasePoolPop(); _objc_autoreleasePoolPush();
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopBeforeWaiting);
/// 7. sleep to wait msg.
mach_msg() -> mach_msg_trap();
/// 8. 通知Observers，线程被唤醒
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopAfterWaiting);
/// 9. 如果是被Timer唤醒的，回调Timer
__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__(timer);
/// 9. 如果是被dispatch唤醒的，执行所有调用 dispatch_async 等方法放入main queue 的 block
__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__(dispatched_block);
/// 9. 如果如果Runloop是被 Source1 (基于port的) 的事件唤醒了，处理这个事件
__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__(source1);
} while (...);
/// 10. 通知Observers，即将退出RunLoop
/// 此处有Observer释放AutoreleasePool: _objc_autoreleasePoolPop();
__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__(kCFRunLoopExit);
}
实现思路：主线程的RunLoop是在应用启动时自动开启的，也没有超时时间，所以正常情况下，主线程的RunLoop 只会在 步骤2—9 之间无限循环下去。
那么，我们只需要在主线程的RunLoop中添加一个observer，检测从 kCFRunLoopBeforeSources 到 kCFRunLoopBeforeWaiting 花费的时间是否过长。如果花费的时间大于某一个阙值，我们就认为有卡顿，并把当前的线程堆栈转储到文件中，并在以后某个合适的时间，将卡顿信息文件上传到服务器。代码如下：
#import <Foundation/Foundation.h>
@interface FluencyMonitor : NSObject
+ (instancetype)shareMonitor;
/**
开始监控
@param interval 定时器间隔时间
@param fault 卡顿的阙值
*/
- (void)startWithInterval:(NSTimeInterval)interval fault:(NSTimeInterval)fault;
/**
开始监控
*/
- (void)start;
/**
停止监控
*/
- (void)stop;
@end
#import "FluencyMonitor.h"
#import <CrashReporter/CrashReporter.h>
@interface FluencyMonitor ()
@property (strong, nonatomic) NSThread *monitorThread; /**< 监控线程 */
@property (assign, nonatomic) CFRunLoopObserverRef observer; /**< 观察者 */
@property (assign, nonatomic) CFRunLoopTimerRef timer; /**< 定时器 */
@property (strong, nonatomic) NSDate *startDate; /**< 开始执行的时间 */
@property (assign, nonatomic) BOOL excuting; /**< 执行时长 */
@property (assign, nonatomic) NSTimeInterval interval; /**< 定时器间隔时间 */
@property (assign, nonatomic) NSTimeInterval fault; /**< 卡顿的阙值 */
@end
@implementation FluencyMonitor
static FluencyMonitor *instance = nil;
/**
第一步：创建一个子线程，在线程启动时，启动其RunLoop
@return <#return value description#>
*/
+ (instancetype)shareMonitor {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
instance = [[[self class] alloc] init];
instance.monitorThread = [[NSThread alloc] initWithTarget:self selector:@selector(monitorThreadEntryPoint) object:nil];
[instance.monitorThread start];
});
return instance;
}
+ (instancetype)allocWithZone:(struct _NSZone *)zone {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
instance = [super allocWithZone:zone];
});
return instance;
}
/**
子线程中启动RunLoop
*/
+ (void)monitorThreadEntryPoint {
@autoreleasepool {
[[NSThread currentThread] setName:@"FluencyMonitor"];
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop addPort:[NSMachPort port] forMode:NSDefaultRunLoopMode];
[runLoop run];
}
}
/**
第二步：开始监控，往主线程的RunLoop中添加一个observer，并往子线程中添加一个定时器，每0.5秒检测一次耗时的时长
*/
- (void)start {
[self startWithInterval:1.0 fault:2.0];
}
/**
开始监控
@param interval 定时器间隔时间
@param fault 卡顿的阙值：超出该阙值则被视为卡顿
*/
- (void)startWithInterval:(NSTimeInterval)interval fault:(NSTimeInterval)fault {
_interval = interval;
_fault = fault;
if (_observer) {
return;
}
// 1.创建observer
CFRunLoopObserverContext context = {0, (__bridge void *)self, NULL, NULL, NULL};
_observer = CFRunLoopObserverCreate(kCFAllocatorDefault, kCFRunLoopAllActivities, YES, 0, &runLoopObserverCallBack, &context);
// 2.将observer添加到主线程的RunLoop中
CFRunLoopAddObserver(CFRunLoopGetMain(), _observer, kCFRunLoopCommonModes);
// 3.创建一个timer，并添加到子线程的RunLoop中
[self performSelector:@selector(addTimerToMonitorThread) onThread:self.monitorThread withObject:nil waitUntilDone:NO modes:@[NSRunLoopCommonModes]];
}
/**
创建一个定时器timer并添加到子线程的RunLoop中
*/
- (void)addTimerToMonitorThread {
if (_timer) {
return;
}
// 1.创建一个timer
CFRunLoopRef currentRunLoop = CFRunLoopGetCurrent();
CFRunLoopTimerContext context = {0, (__bridge void *)self, NULL, NULL, NULL};
_timer = CFRunLoopTimerCreate(kCFAllocatorDefault, 0.1, _interval, 0, 0, &runLoopTimerCallBack, &context);
// 2.添加到子线程的RunLoop中
CFRunLoopAddTimer(currentRunLoop, _timer, kCFRunLoopCommonModes);
}
/**
移除定时器
*/
- (void)removeTimer {
if (_timer) {
CFRunLoopRef currentRunLoop = CFRunLoopGetCurrent();
CFRunLoopRemoveTimer(currentRunLoop, _timer, kCFRunLoopCommonModes);
CFRelease(_timer);
_timer = NULL;
}
}
/**
从主线程中移除观察者observer
*/
- (void)stop {
if (_observer) {
CFRunLoopRemoveObserver(CFRunLoopGetMain(), _observer, kCFRunLoopCommonModes);
CFRelease(_observer);
_observer = NULL;
}
[self performSelector:@selector(removeTimer) onThread:self.monitorThread withObject:nil waitUntilDone:NO modes:@[NSRunLoopCommonModes]];
}
/**
处理卡顿信息：如上传到服务器等
*/
- (void)handleStackInfo {
NSData *lagData = [[[PLCrashReporter alloc] initWithConfiguration:[[PLCrashReporterConfig alloc] initWithSignalHandlerType:PLCrashReporterSignalHandlerTypeBSD symbolicationStrategy:PLCrashReporterSymbolicationStrategyAll]] generateLiveReport];
PLCrashReport *lagReport = [[PLCrashReport alloc] initWithData:lagData error:NULL];
NSString *lagReportString = [PLCrashReportTextFormatter stringValueForCrashReport:lagReport withTextFormat:PLCrashReportTextFormatiOS];
//将字符串上传服务器
NSLog(@"lag happen, detail below: \n %@", lagReportString);
}
/**
观察者回调处理：主线程中的block、交互事件、以及其他任务都是在kCFRunLoopBeforeSources 到 kCFRunLoopBeforeWaiting 之前执行，所以我在即将开始执行Sources 时，记录一下时间，并把正在执行任务的标记置为YES，将要进入睡眠状态时，将正在执行任务的标记置为NO
@param observer <#observer description#>
@param activity <#activity description#>
@param info <#info description#>
*/
static void runLoopObserverCallBack(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info) {
FluencyMonitor *monitor = (__bridge FluencyMonitor *)info;
NSLog(@"MainRunLoop---%@", [NSThread currentThread]);
switch (activity) {
case kCFRunLoopEntry:
NSLog(@"kCFRunLoopEntry");
break;
case kCFRunLoopBeforeTimers:
NSLog(@"kCFRunLoopBeforeTimers");
break;
case kCFRunLoopBeforeSources:
NSLog(@"kCFRunLoopBeforeSources");
monitor.startDate = [NSDate date];
monitor.excuting = YES;
break;
case kCFRunLoopBeforeWaiting:
NSLog(@"kCFRunLoopBeforeWaiting");
monitor.excuting = NO;
break;
case kCFRunLoopAfterWaiting:
NSLog(@"kCFRunLoopAfterWaiting");
break;
case kCFRunLoopExit:
NSLog(@"kCFRunLoopExit");
break;
default:
break;
}
}
/**
定时器回调
@param timer <#timer description#>
@param info <#info description#>
*/
static void runLoopTimerCallBack(CFRunLoopTimerRef timer, void *info) {
FluencyMonitor *monitor = (__bridge FluencyMonitor *)info;
if (!monitor.excuting) {
return;
}
// 如果主线程正在执行任务，并且这一次loop执行到 现在还没执行完，那就需要计算时间差
NSTimeInterval excuteTime = [[NSDate date] timeIntervalSinceDate:monitor.startDate];
NSLog(@"定时器---%@", [NSThread currentThread]);
NSLog(@"主线程执行了---%f秒", excuteTime);
if (excuteTime >= monitor.fault) {
// 执行时间大于阈值时处理卡顿信息
NSLog(@"线程卡顿了%f秒", excuteTime);
[monitor handleStackInfo];
}
}
@end
