NSThread
哎呀，它面向对象，再去看看苹果提供的API，对比一下Pthreads，简单明了，人生仿佛又充满了阳光和希望，我们先来一看一下系统提供给我们的API自然就知道怎么用了，来来来，我给你注释一下啊：
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@interface NSThread : NSObject//当前线程@property (class, readonly, strong) NSThread *currentThread;//使用类方法创建线程执行任务+ (void)detachNewThreadWithBlock:(void (^)(void))block API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0));+ (void)detachNewThreadSelector:(SEL)selector toTarget:(id)target withObject:(nullable id)argument;//判断当前是否为多线程+ (BOOL)isMultiThreaded;//指定线程的线程参数，例如设置当前线程的断言处理器。@property (readonly, retain) NSMutableDictionary *threadDictionary;//当前线程暂停到某个时间+ (void)sleepUntilDate:(NSDate *)date;//当前线程暂停一段时间+ (void)sleepForTimeInterval:(NSTimeInterval)ti;//退出当前线程+ (void)exit;//当前线程优先级+ (double)threadPriority;//设置当前线程优先级+ (BOOL)setThreadPriority:(double)p;//指定线程对象优先级 0.0～1.0，默认值为0.5@property double threadPriority NS_AVAILABLE(10_6, 4_0);//服务质量@property NSQualityOfService qualityOfService NS_AVAILABLE(10_10, 8_0);//线程名称@property (nullable, copy) NSString *name NS_AVAILABLE(10_5, 2_0);//栈区大小@property NSUInteger stackSize NS_AVAILABLE(10_5, 2_0);//是否为主线程@property (class, readonly) BOOL isMainThread NS_AVAILABLE(10_5, 2_0);//获取主线程@property (class, readonly, strong) NSThread *mainThread NS_AVAILABLE(10_5, 2_0);//初始化- (instancetype)init NS_AVAILABLE(10_5, 2_0) NS_DESIGNATED_INITIALIZER;//实例方法初始化，需要再调用start方法- (instancetype)initWithTarget:(id)target selector:(SEL)selector object:(nullable id)argument NS_AVAILABLE(10_5, 2_0);- (instancetype)initWithBlock:(void (^)(void))block API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0));//线程状态，正在执行@property (readonly, getter=isExecuting) BOOL executing NS_AVAILABLE(10_5, 2_0);//线程状态，正在完成@property (readonly, getter=isFinished) BOOL finished NS_AVAILABLE(10_5, 2_0);//线程状态，已经取消@property (readonly, getter=isCancelled) BOOL cancelled NS_AVAILABLE(10_5, 2_0);//取消，仅仅改变线程状态，并不能像exist一样真正的终止线程- (void)cancel NS_AVAILABLE(10_5, 2_0);//开始- (void)start NS_AVAILABLE(10_5, 2_0);//线程需要执行的代码，一般写子类的时候会用到- (void)main NS_AVAILABLE(10_5, 2_0);@end另外，还有一个NSObject的分类，瞅一眼：@interface NSObject (NSThreadPerformAdditions)//隐式的创建并启动线程，并在指定的线程（主线程或子线程）上执行方法。- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<nsstring *> *)array;- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait;- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<nsstring *> *)array NS_AVAILABLE(10_5, 2_0);- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait NS_AVAILABLE(10_5, 2_0);- (void)performSelectorInBackground:(SEL)aSelector withObject:(nullable id)arg NS_AVAILABLE(10_5, 2_0);@end</nsstring *></nsstring *> |
上面的介绍您还满意吗？小的帮您下载一张图片，您瞧好：
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-(void)creatBigImageView{ self.bigImageView = [[UIImageView alloc] initWithFrame:self.view.bounds]; [self.view addSubview:_bigImageView]; UIButton *startButton = [UIButton buttonWithType:UIButtonTypeSystem]; startButton.frame = CGRectMake(0, 0, self.view.frame.size.width / 2, 50); startButton.backgroundColor = [UIColor grayColor]; [startButton setTitle:@"开始加载" forState:UIControlStateNormal]; [startButton addTarget:self action:@selector(loadImage) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:startButton]; UIButton *jamButton = [UIButton buttonWithType:UIButtonTypeSystem]; jamButton.frame = CGRectMake(self.view.frame.size.width / 2, 0, self.view.frame.size.width / 2, 50); jamButton.backgroundColor = [UIColor grayColor]; [jamButton setTitle:@"阻塞测试" forState:UIControlStateNormal]; [jamButton addTarget:self action:@selector(jamTest) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:jamButton];}-(void)jamTest{ UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"线程阻塞" message:@"" delegate:nil cancelButtonTitle:@"好" otherButtonTitles:nil, nil]; [alertView show];}-(void)loadImage{ NSURL *imageUrl = [NSURL URLWithString:@"http://img5.duitang.com/uploads/item/201206/06/20120606174422_LZSeE.thumb.700_0.jpeg"]; NSData *imageData = [NSData dataWithContentsOfURL:imageUrl]; [self updateImageData:imageData];}-(void)updateImageData:(NSData*)imageData{ UIImage *image = [UIImage imageWithData:imageData]; self.bigImageView.image = image;} |
运行结果：
我们可以清楚的看到，主线程阻塞了，用户不可以进行其他操作，你见过这样的应用吗？
所以我们这样改一下：
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-(void)creatBigImageView{ self.bigImageView = [[UIImageView alloc] initWithFrame:self.view.bounds]; [self.view addSubview:_bigImageView]; UIButton *startButton = [UIButton buttonWithType:UIButtonTypeSystem]; startButton.frame = CGRectMake(0, 20, self.view.frame.size.width / 2, 50); startButton.backgroundColor = [UIColor grayColor]; [startButton setTitle:@"开始加载" forState:UIControlStateNormal]; [startButton addTarget:self action:@selector(loadImageWithMultiThread) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:startButton]; UIButton *jamButton = [UIButton buttonWithType:UIButtonTypeSystem]; jamButton.frame = CGRectMake(self.view.frame.size.width / 2, 20, self.view.frame.size.width / 2, 50); jamButton.backgroundColor = [UIColor grayColor]; [jamButton setTitle:@"阻塞测试" forState:UIControlStateNormal]; [jamButton addTarget:self action:@selector(jamTest) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:jamButton];}-(void)jamTest{ UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"阻塞测试" message:@"" delegate:nil cancelButtonTitle:@"好" otherButtonTitles:nil, nil]; [alertView show];}-(void)loadImageWithMultiThread{ //方法1：使用对象方法 //NSThread *thread=[[NSThread alloc]initWithTarget:self selector:@selector(loadImage) object:nil]; //??启动一个线程并非就一定立即执行，而是处于就绪状态，当CUP调度时才真正执行 //[thread start]; //方法2：使用类方法 [NSThread detachNewThreadSelector:@selector(loadImage) toTarget:self withObject:nil];}-(void)loadImage{ NSURL *imageUrl = [NSURL URLWithString:@"http://img5.duitang.com/uploads/item/201206/06/20120606174422_LZSeE.thumb.700_0.jpeg"]; NSData *imageData = [NSData dataWithContentsOfURL:imageUrl]; //必须在主线程更新UI，Object：代表调用方法的参数,不过只能传递一个参数(如果有多个参数请使用对象进行封装)，waitUntilDone:是否线程任务完成执行 [self performSelectorOnMainThread:@selector(updateImageData:) withObject:imageData waitUntilDone:YES]; //[self updateImageData:imageData];}-(void)updateImageData:(NSData*)imageData{ UIImage *image = [UIImage imageWithData:imageData]; self.bigImageView.image = image;} |
运行结果：
哎呀，用多线程果然能解决线程阻塞的问题，并且NSThread也比Pthreads好用，仿佛你对精通熟练使用多线程又有了一丝丝曙光。假如我有很多不同类型的任务，每个任务之间还有联系和依赖，你是不是又懵逼了，上面的你是不是觉得又白看了，其实开发中我觉得NSThread用到最多的就是[NSThread currentThread];了。（不要慌，往下看... ...）
