-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event

{

    [NSThread detachNewThreadSelector:@selector(download) toTarget:self withObject:nil];

}

#pragma mark ----------------------

#pragma Methods

//开子线程下载图片,回到主线程刷新UI

-(void)download

{

    //1.确定URL

    NSURL *url = [NSURL URLWithString:@"http://img4.duitang.com/uploads/blog/201310/18/20131018213446_smUw4.thumb.700_0.jpeg"];

    //2.根据url下载图片二进制数据到本地

    NSData *imageData = [NSData dataWithContentsOfURL:url];

    //3.转换图片格式

    UIImage *image = [UIImage imageWithData:imageData];

    NSLog(@"download----%@",[NSThread currentThread]);

    //4.回到主线程显示UI

    /*

     第一个参数:回到主线程要调用哪个方法

     第二个参数:前面方法需要传递的参数 此处就是image

     第三个参数:是否等待

     */

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

 [self performSelector:@selector(showImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:YES];

//    self.imageView.image = image;

    NSLog(@"---end---");

}

//更新UI操作

-(void)showImage:(UIImage *)image

{

    self.imageView.image = image;

    NSLog(@"UI----%@",[NSThread currentThread]);

}