GCD线程间通信及合成图片、获取验证码

The GCD communication between threads and synthetic images, access authentication code

中文介绍

Grand Central Dispatch (GCD)是 Apple 开发的一个多核编程的解决方法。该方法在 Mac OS X 10.6 雪豹中首次推出，并随后被引入到了 iOS4.0中。GCD 是一个替代诸如 NSThread, NSOperationQueue, NSInvocationOperation 等技术的很高效和强大的技术。
GCD 和 block的配合使用，可以方便地进行多线程编程。

Github

Clone

git clone https://github.com/KingComeFromChina/GCD.git

Screenshots

任务和队列

1.任务分为同步任务和异步任务，队列分为串行和并行
2.同步任务不会开线程，异步任务会开线程

- (void)sync_queue:(dispatch_queue_t)queue{

    //同步任务
    dispatch_sync(queue, ^{
        NSLog(@"同步1 - %@",[NSThread currentThread]);
    });
    
    dispatch_sync(queue, ^{
        NSLog(@"同步2 - %@",[NSThread currentThread]);
    });
    
    dispatch_sync(queue, ^{
        NSLog(@"同步3 - %@",[NSThread currentThread]);
    });
    
    dispatch_sync(queue, ^{
        NSLog(@"同步4 - %@",[NSThread currentThread]);
    });
}

- (void)async_queue:(dispatch_queue_t)queue{
    
    //异步任务
    dispatch_async(queue, ^{
        NSLog(@"异步1 - %@",[NSThread currentThread]);
    });
    
    dispatch_async(queue, ^{
        NSLog(@"异步2 - %@",[NSThread currentThread]);
    });
    
    dispatch_async(queue, ^{
        NSLog(@"异步3 - %@",[NSThread currentThread]);
    });
    
    dispatch_async(queue, ^{
        NSLog(@"异步4 - %@",[NSThread currentThread]);
    });
}

3.串行队列一个一个的执行，并行队列一起执行

同步任务

dispatch_sync(<#dispatch_queue_t _Nonnull queue#>, <#^(void)block#>)

异步任务

dispatch_async(<#dispatch_queue_t _Nonnull queue#>, <#^(void)block#>)

主队列

dispatch_queue_t mainQueue = dispatch_get_main_queue();

全局并发队列

dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

自定义串行队列

dispatch_queue_t serialQueue = dispatch_queue_create("wanglei", NULL);

自定义并行队列

dispatch_queue_t concurrentQueue = dispatch_queue_create("king", DISPATCH_QUEUE_CONCURRENT);

同步主线程会卡死，造成死循环

[self sync_queue:mainQueue];

异步主线程不会开线程，顺序执行

[self async_queue:mainQueue];

同步全局并发不会开线程，顺序执行

[self sync_queue:globalQueue];

异步全局并发会开线程，乱序执行

[self async_queue:globalQueue];

同步串行不会开线程，顺序执行

[self sync_queue:serialQueue];

异步串行会开线程，顺序执行

[self async_queue:serialQueue];

同步并行不会开线程，顺序执行

[self sync_queue:concurrentQueue];

异步并行会开线程，乱序执行

[self async_queue:concurrentQueue];

线程间通信

#pragma mark - 线程间通讯
- (void)threadCommunication{

    //主队列
    dispatch_queue_t mainQueue = dispatch_get_main_queue();
    //全局并发队列
    dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    
    dispatch_async(globalQueue, ^{
        
        NSURL *url = [NSURL URLWithString:@""];
        NSData *data = [[NSData alloc]initWithContentsOfURL:url];
        NSLog(@"%@",[NSThread currentThread]);
        
        dispatch_async(mainQueue, ^{
            
            data;
            //在这里刷新UI
            NSLog(@"mainQueue -- %@",[NSThread currentThread]);
        });
    });
}

GCD创建单例

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        NSLog(@"只执行一次");
    });
}

GCD创建分组任务

- (void)dispatch_group{

    // 创建一个分组
    dispatch_group_t group = dispatch_group_create();
    
    // 全局队列
    dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    
    // 第一个参数: 任务所在的分组
    // 第二个参数: 任务所在的队列
    
    dispatch_group_async(group, globalQueue, ^{
        NSLog(@"分组任务1");
    });
    
    dispatch_group_async(group, globalQueue, ^{
        NSLog(@"分组任务2");
    });
    
    // 当上面两个任务都完成以后，会执行这个方法，我们在这里处理我们的需求
    dispatch_group_notify(group, globalQueue, ^{
        NSLog(@"上面分组任务完成后，才会执行");
    });
}

GCD延迟操作

- (void)dosomethingByTime{

    // 延迟加载函数
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(10 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        NSLog(@"延迟10s加载");
    });
    
    // 自定义并行队列
    dispatch_queue_t concurrentQueue = dispatch_queue_create("wanglei", DISPATCH_QUEUE_CONCURRENT);
    
    dispatch_async(concurrentQueue, ^{
        NSLog(@"dispatch_async - 1-%@",[NSThread currentThread]);
    });
    
    dispatch_async(concurrentQueue, ^{
        NSLog(@"dispatch_async - 2-%@",[NSThread currentThread]);
    });
    
    // dispatch_barrier_async 使用于并行环境下
    // 使用dispatch_barrier_async添加的任务会在之前的block全部运行完毕之后，才会继续执行。保证对非线程安全的对象进行正确的操作
    // 运行完dispatch_barrier_async的block才会执行后面的任务
    // dispatch_barrier_async所在的线程跟前一个任务是同一条线程
    dispatch_barrier_async(concurrentQueue, ^{
        NSLog(@"dispatch_barrier_async-%@",[NSThread currentThread]);
    });
    
    dispatch_barrier_async(concurrentQueue, ^{
        NSLog(@"dispatch_barrier_async- 3 -%@",[NSThread currentThread]);
    });
    
    dispatch_barrier_async(concurrentQueue, ^{
        NSLog(@"dispatch_barrier_async- 4 -%@",[NSThread currentThread]);
    });

}

GCD下载图片及合成

- (void)drawRectImage{

    // 创建全局并发队列
    dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    
    // 异步下载
    dispatch_async(globalQueue, ^{
        
        // 下载第一张图片
        NSURL *url1 = [NSURL URLWithString:@"http://pic6.huitu.com/res/20130116/84481_20130116142820494200_1.jpg"];
        NSData *data1 = [NSData dataWithContentsOfURL:url1];
        UIImage *image1 = [UIImage imageWithData:data1];
        
        // 下载第二张图片
        NSURL *url2 = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/c2cec3fdfc03924578c6cfe18394a4c27c1e25e8.jpg"];
        NSData *data2 = [NSData dataWithContentsOfURL:url2];
        UIImage *image2 = [UIImage imageWithData:data2];
        
        // 合并图片
        // 开启一个位图上下文
        UIGraphicsBeginImageContextWithOptions(image1.size, NO, 0.0);
        
        // 绘制第一张图片
        CGFloat image1Width = image1.size.width;
        CGFloat image1Height = image1.size.height;
        [image1 drawInRect:CGRectMake(0, 0, image1Width, image1Height)];
        
        // 绘制第二张图片
        CGFloat image2Width = image2.size.width * 0.5;
        CGFloat image2Height = image2.size.height * 0.5;
        CGFloat image2Y = image1Height - image2Height;
        [image2 drawInRect:CGRectMake(0, image2Y, image2Width, image2Height)];
        
        // 得到上下文中的图片
        UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext();
        
        // 结束上下文
        UIGraphicsEndImageContext();
        
        // 回到主线程显示图片
        
        dispatch_queue_t mainQueue = dispatch_get_main_queue();
        dispatch_async(mainQueue, ^{
            self.imageView.image = fullImage;
        });
    });
}

GCD实现的验证码倒计时

- (void)btnClick{

    
    
     [_btn setTitle:@"重发(60s)" forState:UIControlStateNormal];
    __block int timeout=59; //倒计时时间
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
    dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行
    dispatch_source_set_event_handler(_timer, ^{
        if(timeout<=0){ //倒计时结束，关闭
            
            dispatch_source_cancel(_timer);
            dispatch_async(dispatch_get_main_queue(), ^{
                //设置界面的按钮显示 根据自己需求设置
                self.btn.userInteractionEnabled = YES;
                [self.btn setTitle:@"获取验证码" forState:UIControlStateNormal];
                
            });
        }else{
            int seconds = timeout % 60;
            NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];
            dispatch_async(dispatch_get_main_queue(), ^{
                //设置界面的按钮显示 根据自己需求设置
                [UIView beginAnimations:nil context:nil];
                [UIView setAnimationDuration:1];
                [self.btn setTitle:[NSString stringWithFormat:@"重发(%@秒)",strTime] forState:UIControlStateNormal];
                
                [UIView commitAnimations];
                self.btn.userInteractionEnabled = NO;
                
            });
            timeout--;
        }
    });
    
    dispatch_resume(_timer);
    



}

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