GCD 大中枢派发 简单应用实例

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@interface ViewController ()

{

    UIImageView* iv;

    UIButton* btn;

    UILabel* lbl;

}

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    iv=[[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];

    lbl=[[UILabel alloc]initWithFrame:CGRectMake(0, 100, 100, 30)];

    btn=[[UIButton alloc]initWithFrame:CGRectMake(0, 130, 100, 30)];

    [btn addTarget:self action:@selector(loadData) forControlEvents:UIControlEventTouchUpInside];

    btn.backgroundColor=[UIColor orangeColor];

    [self.view addSubview:iv];

    [self.view addSubview:lbl];

    [self.view addSubview:btn];

}

-(void)loadData

{

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{

        NSString* url=@"http://f4.topitme.com/4/e4/5e/1132253263b8b5ee44o.jpg";

        NSData* data=[[NSData alloc]initWithContentsOfURL:[NSURL URLWithString:url]];

        UIImage* image=[[UIImage alloc]initWithData:data];

        if (image) {

            dispatch_async(dispatch_get_main_queue(), ^{

                self->iv.image=image;

            });

        }

        else

        {

            NSLog(@"下载错误");

        }

    });

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{

        NSString* str=@"123";

        if (str) {

            dispatch_async(dispatch_get_main_queue(), ^{

                self->lbl.text=str;

            });

        }

        else

        {

            NSLog(@"下载错误");

        }

    });

}

GCD 大中枢派发 简单应用实例

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原文地址：http://www.cnblogs.com/death3721/p/5045635.html