0829多线程

#import "WhyViewController.h"

@interface WhyViewController ()

@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@property (weak, nonatomic) IBOutlet UIActivityIndicatorView *indicator;

@end

@implementation WhyViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self downLoadImageUseOperationQueue];
}

#pragma mark - 下载图像方法一：使用NSOperationQueue
- (void)downLoadImageUseOperationQueue
{
    NSString *url = @"http://avatar.youkuaiyun.com/2/C/D/1_totogo2010.jpg";
    NSInvocationOperation *operator = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(downLoadImage:) object:url];
    NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    [queue addOperation:operator];
}
#pragma mark - 线程任务
- (void)downLoadImage:(NSString *)urlPath
{
    NSURL *url = [NSURL URLWithString:urlPath];
    NSData *data = [[NSData alloc]initWithContentsOfURL:url];
    UIImage *image = [[UIImage alloc]initWithData:data];
    
    [self performSelectorOnMainThread:@selector(updateUI:) withObject:image waitUntilDone:YES];
    
}
#pragma mark - 更新UI
- (void)updateUI:(UIImage *)image
{
    self.imageView.image = image;
}


#pragma mark - 下载图像方法二：使用GCD
- (void)downLoadImageUseGCD
{
    [self.indicator startAnimating];
    self.indicator.hidesWhenStopped = YES;
    
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSURL *url = [NSURL URLWithString:@"http://avatar.youkuaiyun.com/2/C/D/1_totogo2010.jpg"];
        NSData *data = [[NSData alloc]initWithContentsOfURL:url];
        UIImage *image = [[UIImage alloc]initWithData:data];
        if (data != nil) {
            dispatch_async(dispatch_get_main_queue(), ^{
                self.imageView.image = image;
                [self.indicator stopAnimating];
            });
        }
    });
}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end