一、GCD的使用
// // IBController3.m // IBCoder1 // // Created by Bowen on 2018/4/25. // Copyright © 2018年 BowenCoder. All rights reserved. // #import "IBController3.h" @interface IBController3 () @end /* 进程:执行中的应用程序【一个应用程序可以有很多进程(网游双开),在iOS中一个app只有一个进程。】 资源分配最小单元 线程:进程中的一个执行序列,执行调度的最小单元 线程与进程的区别: a.地址空间和其它资源:进程间拥有独立内存,进程是资源分配的基本单位;线程隶属于某一进程,且同一进程的各线程间共享内存(资源),线程是cpu调度的基本单位。 b.通信:进程间相互独立,通信困难,常用的方法有:管道,信号,套接字,共享内存,消息队列等;线程间可以直接读写进程数据段(如全局变量)来进行通信——需要进程同步和互斥手段的辅助,以保证数据的一致性。 c.调度和切换:线程上下文切换比进程上下文切换要快。进程间切换要保存上下文,加载另一个进程;而线程则共享了进程的上下文环境,切换更快。 一、简介 1.什么是GCD 全称是Grand Central Dispatch,可译为“牛逼的中枢调度器” 纯C语言,提供了非常多强大的函数 2.GCD的优势 GCD是苹果公司为多核的并行运算提出的解决方案 GCD会自动利用更多的CPU内核(比如双核、四核) GCD会自动管理线程的生命周期(创建线程、调度任务、销毁线程) 程序员只需要告诉GCD想要执行什么任务,不需要编写任何线程管理代码 二、任务和队列 1.GCD中有2个核心概念 任务:执行什么操作 队列:用来存放任务 2.GCD的使用就2个步骤 定制任务 确定想做的事情 3.将任务添加到队列中 GCD会自动将队列中的任务取出,放到对应的线程中执行 任务的取出遵循队列的FIFO原则:先进先出,后进后出 三、执行任务 1.GCD中有2个用来执行任务的函数 用同步的方式执行任务 dispatch_sync(dispatch_queue_t queue, dispatch_block_t block); queue:队列 block:任务 2.用异步的方式执行任务 dispatch_async(dispatch_queue_t queue, dispatch_block_t block); 3.同步和异步的区别 同步:只能在当前线程中执行任务,不具备开启新线程的能力 异步:可以在新的线程中执行任务,具备开启新线程的能力 四、队列的类型 1.GCD的队列可以分为2大类型 并发队列(Concurrent Dispatch Queue) 可以让多个任务并发(同时)执行(自动开启多个线程同时执行任务) 并发功能只有在异步(dispatch_async)函数下才有效 2.串行队列(Serial Dispatch Queue) 让任务一个接着一个地执行(一个任务执行完毕后,再执行下一个任务) 五、容易混淆的术语 1.有4个术语比较容易混淆:同步、异步、并发、串行 同步和异步主要影响:能不能开启新的线程 同步:在当前线程中执行任务,不具备开启新线程的能力 异步:在新的线程中执行任务,具备开启新线程的能力 2.并发和串行主要影响:任务的执行方式 并发:多个任务并发(同时)执行 串行:一个任务执行完毕后,再执行下一个任务 六、并发队列 1.GCD默认已经提供了全局的并发队列,供整个应用使用,不需要手动创建 使用dispatch_get_global_queue函数获得全局的并发队列 dispatch_queue_t dispatch_get_global_queue( dispatch_queue_priority_t priority, // 队列的优先级 unsigned long flags); // 此参数暂时无用,用0即可 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); // 获得全局并发队列 2.全局并发队列的优先级 #define DISPATCH_QUEUE_PRIORITY_HIGH 2 // 高 #define DISPATCH_QUEUE_PRIORITY_DEFAULT 0 // 默认(中) #define DISPATCH_QUEUE_PRIORITY_LOW (-2) // 低 #define DISPATCH_QUEUE_PRIORITY_BACKGROUND INT16_MIN // 后台 七、串行队列 1.GCD中获得串行有2种途径 使用dispatch_queue_create函数创建串行队列 dispatch_queue_t dispatch_queue_create(const char *label, // 队列名称 dispatch_queue_attr_t attr); // 队列属性,一般用NULL即可 dispatch_queue_t queue = dispatch_queue_create("cn.itcast.queue", NULL); // 创建 dispatch_release(queue); // 非ARC需要释放手动创建的队列 2.使用主队列(跟主线程相关联的队列) 主队列是GCD自带的一种特殊的串行队列 放在主队列中的任务,都会放到主线程中执行 使用dispatch_get_main_queue()获得主队列 dispatch_queue_t queue = dispatch_get_main_queue(); 八、各种队列的执行效果 注意 使用sync函数往当前串行队列中添加任务,会卡住当前的串行队列 九、线程间通信示例 1.从子线程回到主线程 dispatch_async( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // 执行耗时的异步操作... dispatch_async(dispatch_get_main_queue(), ^{ // 回到主线程,执行UI刷新操作 }); }); 十、延时执行 iOS常见的延时执行有2种方式 调用NSObject的方法 [self performSelector:@selector(run) withObject:nil afterDelay:2.0]; // 2秒后再调用self的run方法 使用GCD函数 dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ // 2秒后执行这里的代码... 在哪个线程执行,跟队列类型有关 }); 十一、一次性代码 使用dispatch_once函数能保证某段代码在程序运行过程中只被执行1次 static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ // 只执行1次的代码(这里面默认是线程安全的) }); 十二、队列组 1.有这么1种需求 首先:分别异步执行2个耗时的操作 其次:等2个异步操作都执行完毕后,再回到主线程执行操作 2.如果想要快速高效地实现上述需求,可以考虑用队列组 dispatch_group_t group = dispatch_group_create(); dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // 执行1个耗时的异步操作 }); dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // 执行1个耗时的异步操作 }); dispatch_group_notify(group, dispatch_get_main_queue(), ^{ // 等前面的异步操作都执行完毕后,回到主线程... }); 十三、Core Foundation Foundation : OC Core Foundation : C Foundation和Core Foundation可以相互转化 NSString *str = @"123"; CFStringRef str2 = (__bridge CFStringRef)str; NSString *str3 = (__bridge NSString *)(str2); CFArrayRef --- NSArray CFDictionaryRef --- NSDirectory CFNumberRef --- NSNumber 凡是函数名中带有createcopy etain ew等字眼,都应该再不需要的时候进行release GCD的数据类型在ARC环境下不需要release CF(Core Foundation)的数据类型在ARC环境下还需要release Core Foundation中手动创建的数据类型,需要手动释放 CFArrayRef array = CFArrayCreate(NULL, NULL, 10, NULL); CFRelease(array); CGPathRef path = CGPathCreateMutable(); CGPathRelease(path); 注意千万分清:主线程和主队列概念 */ @implementation IBController3 - (void)viewDidLoad { [super viewDidLoad]; self.view.backgroundColor = [UIColor whiteColor]; } - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event { NSLog(@"-------------------------------------"); // [self test1]; // [self test2]; // [self test3]; // [self test4]; // [self test5]; // [self test6]; [self test7]; // [self test8]; // [self test9]; NSLog(@"++++++++++++++++++++++++++++++++++++"); } /** 同步主队列 在主线程中执行 理解:主队列在同步任务的条件下,必须主线程空闲的时候,才可以添加任务到队列中 */ - (void)test9 { dispatch_queue_t queue = dispatch_get_main_queue(); dispatch_sync(queue, ^{ NSLog(@"----1----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----2----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----3----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----4----%@",[NSThread currentThread]); }); } /** * sync(同步) --串行队列 * 会不会创建线程:不会 * 线程的执行方法:串行(一个任务执行完毕后,再执行下一个任务) * 在主线程中执行串行队列,完成后回到主线程在执行主队列 */ - (void)test8 { dispatch_queue_t queue = dispatch_queue_create("bowen", DISPATCH_QUEUE_SERIAL); dispatch_sync(queue, ^{ NSLog(@"----1----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----2----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----3----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----4----%@",[NSThread currentThread]); }); } /** * sync(同步) --并发队列 * 会不会创建线程:不会,在主线程中运行 * 任务的执行方式:串行(一个任务执行完毕后,再执行下一个任务) * 并发队列失去并发功能 * 在主线程中执行并发队列,完成后回到主线程执行主队列 */ - (void)test7 { dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_sync(queue, ^{ NSLog(@"----1----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----2----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----3----%@",[NSThread currentThread]); }); dispatch_sync(queue, ^{ NSLog(@"----4----%@",[NSThread currentThread]); }); } /** * async(异步) --主队列(很常用)(特殊) * 会不会创建线程:不会 * 任务的执行方式:串行 * 一般用在线程之间的通讯 * 理解:异步主队列,先把任务添加到主队列中,等主线程空闲执行任务 */ - (void)test6 { dispatch_queue_t queue = dispatch_get_main_queue(); dispatch_async(queue, ^{ NSLog(@"----1----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----2----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----3----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----4----%@",[NSThread currentThread]); }); } /** * async(异步) --串行队列(有时用) * 会不会创建线程:会,创建一条 * 线程的执行方法:串行(一个任务执行完毕后,再执行下一个任务) */ - (void)test5 { dispatch_queue_t queue = dispatch_queue_create("bowen", DISPATCH_QUEUE_SERIAL); dispatch_async(queue, ^{ NSLog(@"----1----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----2----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----3----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----4----%@",[NSThread currentThread]); }); } /** * async(异步) --并发队列(最常用) * 会不会创建线程:会,并且创建多条线程 * 任务的执行方式:并发执行 */ - (void)test4 { dispatch_queue_t queue = dispatch_queue_create("bowen", DISPATCH_QUEUE_CONCURRENT); dispatch_async(queue, ^{ NSLog(@"----1----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----2----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----3----%@",[NSThread currentThread]); }); dispatch_async(queue, ^{ NSLog(@"----4----%@",[NSThread currentThread]); }); } /** 组内并行,组间串行 */ - (void)test1 { dispatch_group_t group1 = dispatch_group_create(); dispatch_queue_t queue1 = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_group_async(group1, queue1, ^{ NSLog(@"group1 --- 1---%@",[NSThread currentThread]); }); dispatch_group_async(group1, queue1, ^{ NSLog(@"group1 --- 2---%@",[NSThread currentThread]); }); dispatch_group_async(group1, queue1, ^{ NSLog(@"group1 --- 3---%@",[NSThread currentThread]); }); dispatch_group_async(group1, queue1, ^{ NSLog(@"group1 --- 4---%@",[NSThread currentThread]); }); dispatch_group_wait(group1,DISPATCH_TIME_FOREVER); dispatch_group_t group2 = dispatch_group_create(); dispatch_queue_t queue2 = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_group_async(group2, queue2, ^{ NSLog(@"group2 --- 1---%@",[NSThread currentThread]); }); dispatch_group_async(group2, queue2, ^{ NSLog(@"group2 --- 2---%@",[NSThread currentThread]); }); dispatch_group_async(group2, queue2, ^{ NSLog(@"group2 --- 3---%@",[NSThread currentThread]); }); dispatch_group_async(group2, queue2, ^{ NSLog(@"group2 --- 4---%@",[NSThread currentThread]); }); } - (void)test2 { NSOperationQueue *oq = [[NSOperationQueue alloc] init]; oq.maxConcurrentOperationCount = 1; [oq addOperationWithBlock:^{ NSLog(@"1--%@",[NSThread currentThread]); }]; [oq addOperationWithBlock:^{ NSLog(@"2--%@",[NSThread currentThread]); }]; [oq addOperationWithBlock:^{ NSLog(@"3--%@",[NSThread currentThread]); }]; [oq addOperationWithBlock:^{ NSLog(@"4--%@",[NSThread currentThread]); }]; } /** 组内串行,组间并行 */ - (void)test3 { dispatch_group_t group1 = dispatch_group_create(); dispatch_queue_t queue1 = dispatch_queue_create("leador", DISPATCH_QUEUE_SERIAL); dispatch_group_async(group1, queue1, ^{ NSLog(@"group1 --- 1---%@",[NSThread currentThread]); }); dispatch_group_async(group1, queue1, ^{ NSLog(@"group1 --- 2---%@",[NSThread currentThread]); }); dispatch_group_async(group1, queue1, ^{ NSLog(@"group1 --- 3---%@",[NSThread currentThread]); }); dispatch_group_async(group1, queue1, ^{ NSLog(@"group1 --- 4---%@",[NSThread currentThread]); }); dispatch_group_t group2 = dispatch_group_create(); dispatch_queue_t queue2 = dispatch_queue_create("leador1", DISPATCH_QUEUE_SERIAL); dispatch_group_async(group2, queue2, ^{ NSLog(@"group2 --- 1---%@",[NSThread currentThread]); }); dispatch_group_async(group2, queue2, ^{ NSLog(@"group2 --- 2---%@",[NSThread currentThread]); }); dispatch_group_async(group2, queue2, ^{ NSLog(@"group2 --- 3---%@",[NSThread currentThread]); }); dispatch_group_async(group2, queue2, ^{ NSLog(@"group2 --- 4---%@",[NSThread currentThread]); }); } @end
二、GCD线程之间通信
1 // 2 // ViewController.m 3 // IOS_0117_GCD通信 4 // 5 // Created by ma c on 16/1/17. 6 // Copyright (c) 2016年 博文科技. All rights reserved. 7 // 8 9 #import "ViewController.h" 10 11 @interface ViewController () 12 13 @property (nonatomic, strong) UIButton *btn; 14 15 @end 16 17 @implementation ViewController 18 19 - (void)viewDidLoad { 20 [super viewDidLoad]; 21 22 self.btn = [UIButton buttonWithType:UIButtonTypeCustom]; 23 [self.btn setFrame:CGRectMake(100, 150, 150, 150)]; 24 [self.btn setBackgroundColor:[UIColor purpleColor]]; 25 [self.view addSubview:self.btn]; 26 } 27 28 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 29 { 30 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); 31 dispatch_async(queue, ^{ 32 33 NSLog(@"download-----%@",[NSThread currentThread]); 34 //子线程下载图片 35 NSURL *url = [NSURL URLWithString:@"http://www.qiyue.com/uploadfile/2016/0103/20160103105808532.jpg"]; 36 NSData *data = [NSData dataWithContentsOfURL:url]; 37 UIImage *image = [UIImage imageWithData:data]; 38 39 //回到主线程 40 dispatch_queue_t mainQueue = dispatch_get_main_queue(); 41 dispatch_async(mainQueue, ^{ 42 43 NSLog(@"刷新---------%@---%@",[NSThread currentThread],image); 44 [self.btn setBackgroundImage:image forState:UIControlStateNormal]; 45 46 }); 47 }); 48 } 49 50 @end
三、延迟执行
1 // 2 // ViewController.m 3 // IOS_0117_GCD线程通信 4 // 5 // Created by ma c on 16/1/17. 6 // Copyright (c) 2016年 博文科技. All rights reserved. 7 // 8 9 #import "ViewController.h" 10 11 @interface ViewController () 12 13 @end 14 15 @implementation ViewController 16 17 - (void)viewDidLoad { 18 [super viewDidLoad]; 19 // Do any additional setup after loading the view, typically from a nib. 20 } 21 22 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 23 { 24 // [self delay1]; 25 // [self delay2]; 26 27 28 } 29 30 - (void)delay3 31 { 32 NSLog(@"-----touchesBegan1------"); 33 //3s后回到主线程执行block代码 34 dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ 35 NSLog(@"-----task------%@",[NSThread currentThread]); 36 }); 37 38 //3s后自动开启新线程执行block代码 39 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); 40 dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), queue, ^{ 41 NSLog(@"-----task------%@",[NSThread currentThread]); 42 }); 43 44 NSLog(@"-----touchesBegan2------"); 45 } 46 47 - (void)delay2 48 { 49 NSLog(@"-----touchesBegan1------"); 50 51 //定制好延迟任务后,不会卡主当前线程 52 [self performSelector:@selector(run) withObject:@"http://" afterDelay:3]; 53 54 NSLog(@"-----touchesBegan2------"); 55 } 56 57 - (void)run:(NSString *)url 58 { 59 NSLog(@"run------%@---%@",[NSThread currentThread], url); 60 } 61 62 - (void)delay1 63 { 64 NSLog(@"------begin------"); 65 66 //延迟线程不要用sleep,坏处:卡主线程 67 [NSThread sleepForTimeInterval:3]; 68 NSLog(@"下载图片"); 69 } 70 @end
四、GCD一次性代码
1 // 2 // ViewController.m 3 // IOS_0117_GCD一次性代码 4 // 5 // Created by ma c on 16/1/17. 6 // Copyright (c) 2016年 博文科技. All rights reserved. 7 // 8 9 #import "ViewController.h" 10 11 @interface ViewController () 12 13 @property (nonatomic, assign) BOOL hasExecuted; 14 15 @end 16 17 @implementation ViewController 18 19 - (void)viewDidLoad { 20 [super viewDidLoad]; 21 // Do any additional setup after loading the view, typically from a nib. 22 } 23 24 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 25 { 26 // [self fun1]; 27 [self fun2]; 28 } 29 30 - (void)fun2 31 { 32 static dispatch_once_t onceToken; 33 dispatch_once(&onceToken, ^{ 34 35 NSLog(@"下载图片"); 36 }); 37 } 38 - (void)fun1 39 { 40 if (self.hasExecuted) return; 41 42 NSLog(@"下载图片"); 43 self.hasExecuted = YES; 44 } 45 46 @end
五、队列组
1 // 2 // HMViewController.m 3 // 03-队列组(了解) 4 // 5 // Created by apple on 14-9-16. 6 // Copyright (c) 2014年 heima. All rights reserved. 7 // 8 9 #import "HMViewController.h" 10 11 // 1.分别下载2张图片:大图片、LOGO 12 // 2.合并2张图片 13 // 3.显示到一个imageView身上 14 15 @interface HMViewController () 16 @property (weak, nonatomic) IBOutlet UIImageView *imageView; 17 @property (nonatomic, strong) UIImage *image1; 18 @property (nonatomic, strong) UIImage *image2; 19 @end 20 21 @implementation HMViewController 22 23 - (void)viewDidLoad 24 { 25 [super viewDidLoad]; 26 27 } 28 29 // 2D绘图 Quartz2D 30 // 合并图片 -- 水印 31 32 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 33 { 34 // 1.队列组 35 dispatch_group_t group = dispatch_group_create(); 36 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); 37 38 // 2.下载图片1 39 __block UIImage *image1 = nil; 40 dispatch_group_async(group, queue, ^{ 41 NSURL *url1 = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/f2deb48f8c5494ee460de6182ff5e0fe99257e80.jpg"]; 42 NSData *data1 = [NSData dataWithContentsOfURL:url1]; 43 image1 = [UIImage imageWithData:data1]; 44 }); 45 46 // 3.下载图片2 47 __block UIImage *image2 = nil; 48 dispatch_group_async(group, queue, ^{ 49 NSURL *url2 = [NSURL URLWithString:@"http://su.bdimg.com/static/superplus/img/logo_white_ee663702.png"]; 50 NSData *data2 = [NSData dataWithContentsOfURL:url2]; 51 image2 = [UIImage imageWithData:data2]; 52 }); 53 54 // 4.合并图片 (保证执行完组里面的所有任务之后,再执行notify函数里面的block) 55 dispatch_group_notify(group, queue, ^{ 56 // 开启一个位图上下文 57 UIGraphicsBeginImageContextWithOptions(image1.size, NO, 0.0); 58 59 // 绘制第1张图片 60 CGFloat image1W = image1.size.width; 61 CGFloat image1H = image1.size.height; 62 [image1 drawInRect:CGRectMake(0, 0, image1W, image1H)]; 63 64 // 绘制第2张图片 65 CGFloat image2W = image2.size.width * 0.5; 66 CGFloat image2H = image2.size.height * 0.5; 67 CGFloat image2Y = image1H - image2H; 68 [image2 drawInRect:CGRectMake(0, image2Y, image2W, image2H)]; 69 70 // 得到上下文中的图片 71 UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext(); 72 73 // 结束上下文 74 UIGraphicsEndImageContext(); 75 76 // 5.回到主线程显示图片 77 dispatch_async(dispatch_get_main_queue(), ^{ 78 self.imageView.image = fullImage; 79 }); 80 }); 81 } 82 83 - (void)test2 84 { 85 // 异步下载 86 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ 87 // 1.下载第1张 88 NSURL *url1 = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/f2deb48f8c5494ee460de6182ff5e0fe99257e80.jpg"]; 89 NSData *data1 = [NSData dataWithContentsOfURL:url1]; 90 self.image1 = [UIImage imageWithData:data1]; 91 92 [self bindImages]; 93 }); 94 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ 95 // 2.下载第2张 96 NSURL *url2 = [NSURL URLWithString:@"http://su.bdimg.com/static/superplus/img/logo_white_ee663702.png"]; 97 NSData *data2 = [NSData dataWithContentsOfURL:url2]; 98 self.image2 = [UIImage imageWithData:data2]; 99 100 [self bindImages]; 101 }); 102 } 103 104 - (void)bindImages 105 { 106 if (self.image1 == nil || self.image2 == nil) return; 107 108 // 3.合并图片 109 // 开启一个位图上下文 110 UIGraphicsBeginImageContextWithOptions(self.image1.size, NO, 0.0); 111 112 // 绘制第1张图片 113 CGFloat image1W = self.image1.size.width; 114 CGFloat image1H = self.image1.size.height; 115 [self.image1 drawInRect:CGRectMake(0, 0, image1W, image1H)]; 116 117 // 绘制第2张图片 118 CGFloat image2W = self.image2.size.width * 0.5; 119 CGFloat image2H = self.image2.size.height * 0.5; 120 CGFloat image2Y = image1H - image2H; 121 [self.image2 drawInRect:CGRectMake(0, image2Y, image2W, image2H)]; 122 123 // 得到上下文中的图片 124 UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext(); 125 126 // 结束上下文 127 UIGraphicsEndImageContext(); 128 129 // 4.回到主线程显示图片 130 dispatch_async(dispatch_get_main_queue(), ^{ 131 self.imageView.image = fullImage; 132 }); 133 } 134 135 - (void)test1 136 { 137 // 异步下载 138 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ 139 // 1.下载第1张 140 NSURL *url1 = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/f2deb48f8c5494ee460de6182ff5e0fe99257e80.jpg"]; 141 NSData *data1 = [NSData dataWithContentsOfURL:url1]; 142 UIImage *image1 = [UIImage imageWithData:data1]; 143 144 // 2.下载第2张 145 NSURL *url2 = [NSURL URLWithString:@"http://su.bdimg.com/static/superplus/img/logo_white_ee663702.png"]; 146 NSData *data2 = [NSData dataWithContentsOfURL:url2]; 147 UIImage *image2 = [UIImage imageWithData:data2]; 148 149 // 3.合并图片 150 // 开启一个位图上下文 151 UIGraphicsBeginImageContextWithOptions(image1.size, NO, 0.0); 152 153 // 绘制第1张图片 154 CGFloat image1W = image1.size.width; 155 CGFloat image1H = image1.size.height; 156 [image1 drawInRect:CGRectMake(0, 0, image1W, image1H)]; 157 158 // 绘制第2张图片 159 CGFloat image2W = image2.size.width * 0.5; 160 CGFloat image2H = image2.size.height * 0.5; 161 CGFloat image2Y = image1H - image2H; 162 [image2 drawInRect:CGRectMake(0, image2Y, image2W, image2H)]; 163 164 // 得到上下文中的图片 165 UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext(); 166 167 // 结束上下文 168 UIGraphicsEndImageContext(); 169 170 // 4.回到主线程显示图片 171 dispatch_async(dispatch_get_main_queue(), ^{ 172 self.imageView.image = fullImage; 173 }); 174 }); 175 } 176 177 @end