iOS----线程之间的通信

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *iconView;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
}

-(void)touchesBegan:(NSSet*)touches withEvent:(UIEvent *)event
{
    [self performSelectorInBackground:@selector(download) withObject:nil];
}
-(void)download
{
    //1.根据URL下载图片
    //从网络中下载图片
    NSURL *urlStr = [NSURL URLWithString:@"asdf"];
     //把图片转换为二进制的数据
    NSData *data = [NSData dataWithContentsOfURL:urlStr];
    //把数据转换成图片
    UIImage *image = [UIImage imageWithData:data];
    //2.回到主线程中设置图片

    [self performSelectorOnMainThread:@selector(settingImage:) withObject:image waitUntilDone:NO];

  　　//第二种方式

  　　  //  [self.imageView performSelector:@selector(setImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:NO];      

　　//第三种方式  :图片调用set方法，很好！！！
    
　　　　//  [self.iconView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:NO];

} 


//设置显示图片 -(void)settingImage:(UIImage *)image { self.iconView.image=image; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; }

@end