//1.使用GCD进行线程处理 ----dispatch_async 使用,避免界面处理耗时的操作时候卡死,先进行线程操作,然后通知主线程更新界面 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ //线程操作 NSInteger row = [indexPath row]; NSString *str = [self.array objectAtIndex:row]; NSURL *url = [NSURL URLWithString:str]; NSData *imageData = [NSData dataWithContentsOfURL:url]; UIImage *image = [[UIImage alloc]initWithData:imageData]; if (image != nil) { dispatch_async(dispatch_get_main_queue(), ^{ cell.imageView.image = image; [cell.activityIndicatorView stopAnimating]; //这里是不能用reloadData的,虽然更新了界面,但是你会发现很多的线程,导致app崩溃。 //[self.tableView reloadData]; //更新界面的操作 }); } });
2.
//2 使用GCD进行线程处理 //dispatch_group_async可以监听一组事件是否完成,完成之后再通知执行其他的操作 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_group_t group = dispatch_group_create(); __block UIImage *image; dispatch_group_async(group, queue, ^{ NSInteger row = [indexPath row]; NSString *str = [self.array objectAtIndex:row]; NSURL *url = [NSURL URLWithString:str]; NSData *imageData = [NSData dataWithContentsOfURL:url]; image = [[UIImage alloc]initWithData:imageData]; }); //只有上面的操作完成之后,才能进行下面的更新操作。 dispatch_group_notify(group, queue, ^{ cell.imageView.image = image; [cell.activityIndicatorView stopAnimating]; });
3.
dispatch_queue_t queue = dispatch_queue_create("gcdtest.rongfzh.yc", DISPATCH_QUEUE_CONCURRENT); dispatch_async(queue, ^{ [NSThread sleepForTimeInterval:2]; NSLog(@"dispatch_async1"); }); dispatch_async(queue, ^{ [NSThread sleepForTimeInterval:4]; NSLog(@"dispatch_async2"); }); dispatch_barrier_async(queue, ^{ NSLog(@"dispatch_barrier_async"); [NSThread sleepForTimeInterval:4]; }); dispatch_async(queue, ^{ [NSThread sleepForTimeInterval:1]; NSLog(@"dispatch_async3"); });
2012-09-25 16:20:33.967 gcdTest[45547:11203] dispatch_async1
2012-09-25 16:20:35.967 gcdTest[45547:11303] dispatch_async2
2012-09-25 16:20:35.967 gcdTest[45547:11303] dispatch_barrier_async
2012-09-25 16:20:40.970 gcdTest[45547:11303] dispatch_async3
4.
4、dispatch_apply
执行某个代码片段N次。
dispatch_apply(5, globalQ, ^(size_t index) {
// 执行5次
});
权威博客:http://blog.csdn.net/totogo2010/article/details/8016129#