NSThread

NSThread

//第一种创建线程的方式：alloc init.
    //特点：需要手动开启线程，可以拿到线程对象进行详细设置
    //创建线程
    /*
     第一个参数：目标对象
     第二个参数：选择器，线程启动要调用哪个方法
     第三个参数：前面方法要接收的参数（最多只能接收一个参数，没有则传nil）
     */
    NSThread *thread = [[NSThread alloc]initWithTarget:self selector:@selector(threadAction1) object:nil];
    //启动线程
    [thread start];
    //设置线程的名称
    thread.name = @"子线程";
    //设置线程的优先级,注意线程优先级的取值范围为0.0~1.0之间，1.0表示线程的优先级最高,如果不设置该值，那么理想状态下默认为0.5
    thread.threadPriority = 1.0;
    
    //第二种创建线程的方式：分离出一条子线程
    //特点：自动启动线程，无法对线程进行更详细的设置
    /*
     第一个参数：线程启动调用的方法
     第二个参数：目标对象
     第三个参数：传递给调用方法的参数
     */
    [NSThread detachNewThreadWithBlock:^{
        NSLog(@"%@",[NSThread currentThread]);
    }];
    
    //第三种创建线程的方式：后台线程
    //特点：自动启动县城，无法进行更详细设置
    [self performSelectorInBackground:@selector(threadAction1) withObject:nil];

GCD

GCD 详解：http://www.jianshu.com/p/d1f9b2a7b0a8

GCD 系统函数

 //0.获取一个全局的队列
    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
    
    //1.先开启一个线程，把下载图片的操作放在子线程中处理
    dispatch_async(queue, ^{
        //2.下载图片
        NSURL *url = [NSURL URLWithString:@"https://ss0.bdstatic.com/5aV1bjqh_Q23odCf/static/superman/img/logo/bd_logo1_31bdc765.png"];
        NSData *imageData = [NSData dataWithContentsOfURL:url];
        NSLog(@"下载操作所在的线程--%@",[NSThread currentThread]);
        //3.回到主线程刷新UI
        dispatch_sync(dispatch_get_main_queue(), ^{
            self.imageView.image = [UIImage imageWithData:imageData];
            NSLog(@"刷新UI---%@",[NSThread currentThread]);
        });
    });

GCD 自定义函数

//1.创建队列
    /*
     第一个参数:C语言的字符串,标签
     第二个参数:队列的类型
     DISPATCH_QUEUE_CONCURRENT:并发
     DISPATCH_QUEUE_SERIAL:串行
     */
    dispatch_queue_t serialQueue = dispatch_queue_create("@download", DISPATCH_QUEUE_SERIAL);
    dispatch_barrier_async(serialQueue, ^{
        
    });
    dispatch_queue_t concurrentQueue = dispatch_queue_create("concurrent", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(concurrentQueue, ^{
        
    });

NSOperation

NSOperation

__weak typeof(self) weakSelf = self;
    //创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    NSURL *url = [NSURL URLWithString: @"https://ss0.bdstatic.com/94oJfD_bAAcT8t7mm9GUKT-xh_/timg?image&quality=100&size=b4000_4000&sec=1504585897&di=7a7b3940fd17b93e2d9a5805cc4e0ccb&src=http://img.zcool.cn/community/01eb6a5542979d0000019ae97e45d6.jpg"];
    NSBlockOperation *downOperation = [NSBlockOperation blockOperationWithBlock:^{
        NSData *imageData = [NSData dataWithContentsOfURL:url options:NSDataReadingUncached error:nil];
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            weakSelf.imageView.image = [UIImage imageWithData:imageData];
        }];
    }];
    [queue addOperation:downOperation];

NSOperation 多图片拼合

NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    //下载图片1
    NSBlockOperation *download1 = [NSBlockOperation blockOperationWithBlock:^{
        self.image1 = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"https://ss0.bdstatic.com/94oJfD_bAAcT8t7mm9GUKT-xh_/timg?image&quality=100&size=b4000_4000&sec=1504585897&di=7a7b3940fd17b93e2d9a5805cc4e0ccb&src=http://img.zcool.cn/community/01eb6a5542979d0000019ae97e45d6.jpg"]]];
    }];
    //下载图片2
    NSBlockOperation *download2 = [NSBlockOperation blockOperationWithBlock:^{
        self.image2 = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"https://ss0.bdstatic.com/94oJfD_bAAcT8t7mm9GUKT-xh_/timg?image&quality=100&size=b4000_4000&sec=1504585897&di=7a7b3940fd17b93e2d9a5805cc4e0ccb&src=http://img.zcool.cn/community/01eb6a5542979d0000019ae97e45d6.jpg"]]];
    }];
    //合并图片
    NSBlockOperation *add = [NSBlockOperation blockOperationWithBlock:^{
        //开启图形上下文
        UIGraphicsBeginImageContext(CGSizeMake(200, 200));
        //画image1
        [self.image1 drawInRect:CGRectMake(0, 0, 200, 100)];
        [self.image2 drawInRect:CGRectMake(0, 100, 200, 100)];
        //根据图形上下文拿到图片数据
        self.addImage = UIGraphicsGetImageFromCurrentImageContext();
        //关闭图形上下文
        UIGraphicsEndImageContext();
        //回到主线程刷新UI
        [[NSOperationQueue mainQueue]addOperationWithBlock:^{
            self.imageView.image  = self.addImage;
        }];
    }];
    
    //设置操作依赖
    [add addDependency:download1];
    [add addDependency:download2];
    //添加操作到队列中执行
    [queue addOperation:download1];
    [queue addOperation:download2];
    [queue addOperation:add];