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[操作系统]iOS中多线程的实现方案


什么是主线程?

一个iOS程序运行后,默认会开启一条线程,称为“主线程”或“UI线程”

 

主线程的主要作用

1.显示/刷新UI界面

2.处理UI事件(比如点击事件,滚动事件,拖拽事件)

 

主线程的使用注意

1.别将比较耗时的操作放在主线程中

2.耗时操作会卡在主线程中,严重影响UI的流畅程度

 

如图,将耗时操作放在主线程中,任务会按照串行顺序执行,在第五秒点击按钮之后,界面会卡住5秒

因为耗时操作还没有执行完,不能立即响应按钮的点击

 

 

1.pthread的使用

void *run(void *parme) {    NSLog(@"%@",[NSThread currentThread]);      for (int i = 0; i < 100000; i++) {    NSLog(@"%d",i);  }  return NULL;  }- (IBAction)btnClick:(id)sender {    pthread_t thread;  pthread_create(&thread, NULL, run, NULL);  }

 

2.NSThread的使用

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {  [self createThread3];}//第一种创建方法- (void)createThread1 {  //需要几个线程就alloc几个  NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(run:) object:@"第一种"];  thread.name = @"one_thread";  [thread start];}//第二种创建方法- (void)createThread2 {    [NSThread detachNewThreadSelector:@selector(run:) toTarget:self withObject:@"第二种"];}//第三种创建方法- (void)createThread3 {    [self performSelectorInBackground:@selector(run:) withObject:@"第三种"];}- (void)run:(NSString *)param {  NSLog(@"______%@_____%@",param,[NSThread currentThread]);}

 

3.GCD的使用

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {  [self syncMain];}/** 同步函数+主队列 */- (void)syncMain {  dispatch_queue_t queue = dispatch_get_main_queue();    NSLog(@"syncMain ---- begin");  //将任务加入到队列  dispatch_sync(queue, ^{    NSLog(@"1----%@",[NSThread currentThread]);  });  dispatch_sync(queue, ^{    NSLog(@"2----%@",[NSThread currentThread]);  });  dispatch_sync(queue, ^{    NSLog(@"3----%@",[NSThread currentThread]);  });    NSLog(@"syncMain ---- end");}/** 异步函数+主队列 */- (void)asyncMain {    //异步函数用在主队列上就不会开线程了  //获得串行队列  dispatch_queue_t queue = dispatch_get_main_queue();    //将任务加入到队列  dispatch_async(queue, ^{    NSLog(@"1----%@",[NSThread currentThread]);  });  dispatch_async(queue, ^{    NSLog(@"2----%@",[NSThread currentThread]);  });  dispatch_async(queue, ^{    NSLog(@"3----%@",[NSThread currentThread]);  });}/** 同步函数+串行队列:不会开启新的线程,在当前线程执行任务 */- (void)syncSerial {  //创建串行队列  dispatch_queue_t queue = dispatch_queue_create("com.520.queue", DISPATCH_QUEUE_SERIAL);    //将任务加入到队列  dispatch_sync(queue, ^{    NSLog(@"1----%@",[NSThread currentThread]);  });  dispatch_sync(queue, ^{    NSLog(@"2----%@",[NSThread currentThread]);  });  dispatch_sync(queue, ^{    NSLog(@"3----%@",[NSThread currentThread]);  });}/** 异步函数+串行队列:会开启新的线程,但是任务是串行的,执行完一个任务,再执行下一个任务 */- (void)asyncSerial {  //创建串行队列  dispatch_queue_t queue = dispatch_queue_create("com.520.queue", DISPATCH_QUEUE_SERIAL);    //将任务加入到队列  dispatch_async(queue, ^{    NSLog(@"1----%@",[NSThread currentThread]);  });  dispatch_async(queue, ^{    NSLog(@"2----%@",[NSThread currentThread]);  });  dispatch_async(queue, ^{    NSLog(@"3----%@",[NSThread currentThread]);  });}/** 同步函数+并发队列:不会开启线程,不能 */- (void)syncConcurrent {  //获得全局的并发队列  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    //将任务添加到队列  dispatch_async(queue, ^{    NSLog(@"1----%@",[NSThread currentThread]);  });  dispatch_async(queue, ^{    NSLog(@"1----%@",[NSThread currentThread]);  });  dispatch_async(queue, ^{    NSLog(@"1----%@",[NSThread currentThread]);  });}/** 异步函数+并发队列:可以同时开启多条线程 */- (void)asycConcurrent {  //创建一个队列  //第一个参数是标签等同于名字  //第二个参数传串行还是并行//  dispatch_queue_t queue = dispatch_queue_create("img.download", DISPATCH_QUEUE_CONCURRENT);  //获得全局的并发队列  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    //将任务添加到队列  dispatch_async(queue, ^{    for (int i = 0; i < 10; i++) {      NSLog(@"1----%@",[NSThread currentThread]);    }  });    //将任务添加到队列  dispatch_async(queue, ^{    for (int i = 0; i < 10; i++) {      NSLog(@"2----%@",[NSThread currentThread]);    }  });    //将任务添加到队列  dispatch_async(queue, ^{    for (int i = 0; i < 10; i++) {      NSLog(@"3----%@",[NSThread currentThread]);    }  });}

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在使用GCD时,主要分为两步

1.定制任务

2.将任务添加到队列

 

这里还需要区分下同步,异步,并行,串行

同步异步:影响是否开启新的线程

并行串行:影响任务的执行方式