-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
22 {
23 
24 // 在子线程中调用download方法下载图片
25     [self performSelectorInBackground:@selector(download) withObject:nil];
26 }
30 -(void)download
31 {
32     //1.根据URL下载图片
33     //从网络中下载图片
34     NSURL *urlstr=[NSURL URLWithString:@"fdsf"];
35 
36     //把图片转换为二进制的数据
37     NSData *data=[NSData dataWithContentsOfURL:urlstr];//这一行操作会比较耗时
38 
39     //把数据转换成图片
40     UIImage *image=[UIImage imageWithData:data];
41  
42     //2.回到主线程中设置图片
43     [self performSelectorOnMainThread:@selector(settingImage:) withObject:image waitUntilDone:NO];
44 }
45 
46  
47 
48 //设置显示图片
49 -(void)settingImage:(UIImage *)image
50 {
51     self.iconView.image=image;
52 }
53 
54 @end

 1 //
 2 //  YYViewController.m
 3 //  06-NSThread04-线程间通信
 4 //
 5 //  Created by apple on 14-6-23.
 6 //  Copyright (c) 2014年 itcase. All rights reserved.
 7 //
 8 
 9 #import "YYViewController.h"
10 #import <NSData.h>
11 
12 @interface YYViewController ()
13 @property (weak, nonatomic) IBOutlet UIImageView *iconView;
14 @end
15 
16 @implementation YYViewController
17 
18 - (void)viewDidLoad
19 {
20     [super viewDidLoad];
21 }
22 
23  
24 -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
25 {
26 // 在子线程中调用download方法下载图片
27 
28     [self performSelectorInBackground:@selector(download) withObject:nil];
29 }
30 
31  
32 -(void)download
33 {
34 
35     //1.根据URL下载图片
36     //从网络中下载图片
37     NSURL *urlstr=[NSURL URLWithString:@"fdsf"];
38 
39     //把图片转换为二进制的数据
40     NSData *data=[NSData dataWithContentsOfURL:urlstr];//这一行操作会比较耗时
41 
42     //把数据转换成图片
43     UIImage *image=[UIImage imageWithData:data];
44 
45     //2.回到主线程中设置图片
46     //第一种方式
47 //    [self performSelectorOnMainThread:@selector(settingImage:) withObject:image waitUntilDone:NO];
48 
49     //第二种方式
50     //    [self.imageView performSelector:@selector(setImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:NO];
51 
52     //第三种方式
53    [self.iconView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:NO];
54 }
55 
56 
57 //设置显示图片
58 //-(void)settingImage:(UIImage *)image
59 //{
60 //    self.iconView.image=image;
61 //}
62 
63 @end