IOS NSThread 线程间通信

@interface HMViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *imageView;

@end

@implementation HMViewController

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

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    // 在子线程中调用download方法下载图片
    [self performSelectorInBackground:@selector(download) withObject:nil];
}

/**
 * 下载图片 : 子线程
 */
- (void)download
{
    // 1.根据URL下载图片
    NSURL *url = [NSURL URLWithString:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];
    NSLog(@"-------begin");
    NSData *data = [NSData dataWithContentsOfURL:url]; // 这行会比较耗时
    NSLog(@"-------end");
    UIImage *image = [UIImage imageWithData:data];

    // 2.回到主线程显示图片
//    [self.imageView performSelector:@selector(setImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:NO];
    // setImage: 1s
    [self.imageView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:NO];
//    [self performSelectorOnMainThread:@selector(settingImage:) withObject:image waitUntilDone:NO];
}

/**
 * 设置(显示)图片: 主线程
 */
//- (void)settingImage:(UIImage *)image
//{
//    self.imageView.image = image
//}