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
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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]); } });}
View Code
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
原标题:iOS中多线程的实现方案
关键词:IOS