1 #import "HMViewController.h"
2
3 @interface HMViewController ()
4 @property (weak, nonatomic) IBOutlet UIImageView *imageView1;
5 @property (weak, nonatomic) IBOutlet UIImageView *imageView2;
6 @property (weak, nonatomic) IBOutlet UIImageView *bigImageView;
7 @end
8
9 @implementation HMViewController
10
11 - (void)viewDidLoad
12 {
13 [super viewDidLoad];
14 // Do any additional setup after loading the view, typically from a nib.
15
16 // 图片1: http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg
17 // 图片2: http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg
18 /**
19 1.下载图片1和图片2
20
21 2.将图片1和图片2合并成一张图片后显示到imageView上
22
23 思考:
24 * 下载图片 : 子线程
25 * 等2张图片都下载完毕后, 才回到主线程
26 */
27 }
28
29 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
30 {
31 // 创建一个组
32 dispatch_group_t group = dispatch_group_create();
33
34 // 开启一个任务下载图片1
35 __block UIImage *image1 = nil;
36 dispatch_group_async(group, global_queue, ^{
37 image1 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];
38 });
39
40 // 开启一个任务下载图片2
41 __block UIImage *image2 = nil;
42 dispatch_group_async(group, global_queue, ^{
43 image2 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg"];
44 });
45
46 // 同时执行下载图片1\下载图片2操作
47
48 // 等group中的所有任务都执行完毕, 再回到主线程执行其他操作
49 dispatch_group_notify(group, main_queue, ^{
50 self.imageView1.image = image1;
51 self.imageView2.image = image2;
52
53 // 合并
54 UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 100), NO, 0.0);
55 [image1 drawInRect:CGRectMake(0, 0, 100, 100)];
56 [image2 drawInRect:CGRectMake(100, 0, 100, 100)];
57 self.bigImageView.image = UIGraphicsGetImageFromCurrentImageContext();
58 // 关闭上下文
59 UIGraphicsEndImageContext();
60 });
61 // if (self.log == NO) {
62 // NSLog(@"-------touchesBegan");
63 // self.log = YES;
64 // }
65 // static dispatch_once_t onceToken;
66 // dispatch_once(&onceToken, ^{
67 // NSLog(@"-------touchesBegan");
68 // });
69 }
70
71 - (void)downlaod2image
72 {
73 dispatch_async(global_queue, ^{
74 NSLog(@"下载图片---%@", [NSThread currentThread]);
75
76 // 下载图片1
77 UIImage *image1 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];
78 NSLog(@"下载完图片1---%@", [NSThread currentThread]);
79 // 下载图片2
80 UIImage *image2 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];
81 NSLog(@"下载完图片2---%@", [NSThread currentThread]);
82
83 dispatch_async(main_queue, ^{
84 NSLog(@"显示图片---%@", [NSThread currentThread]);
85
86 self.imageView1.image = image1;
87 self.imageView2.image = image2;
88
89 // 合并
90 UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 100), NO, 0.0);
91 [image1 drawInRect:CGRectMake(0, 0, 100, 100)];
92 [image2 drawInRect:CGRectMake(100, 0, 100, 100)];
93 self.bigImageView.image = UIGraphicsGetImageFromCurrentImageContext();
94 // 关闭上下文
95 UIGraphicsEndImageContext();
96 });
97 });
98 }
99
100 - (UIImage *)imageWithURL:(NSString *)urlStr
101 {
102 NSURL *url = [NSURL URLWithString:urlStr];
103 NSData *data = [NSData dataWithContentsOfURL:url]; // 这行会比较耗时
104 return [UIImage imageWithData:data];
105 }
106
107 - (void)delay
108 {
109 // NSLog(@"----touchesBegan----%@", [NSThread currentThread]);
110
111 // dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
112 // [self performSelector:@selector(run) withObject:nil afterDelay:2.0];
113 // });
114 // 1.全局并发队列
115 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
116
117 // 2.计算任务执行的时间
118 dispatch_time_t when = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5.0 * NSEC_PER_SEC));
119
120 // 3.会在when这个时间点, 执行queue中的任务
121 dispatch_after(when, queue, ^{
122 NSLog(@"----run----%@", [NSThread currentThread]);
123 });
124 }
125
126 @end
