NSOperation的基本使用

Paste_Image.png

Paste_Image.png

案例多图下载

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [self blockOperation];
}

- (void)blockOperation
{
    NSBlockOperation *op = [NSBlockOperation blockOperationWithBlock:^{
        // 在主线程
        NSLog(@"下载1------%@", [NSThread currentThread]);
    }];
    
    // 添加额外的任务(在子线程执行)
    [op addExecutionBlock:^{
        NSLog(@"下载2------%@", [NSThread currentThread]);
    }];

    [op addExecutionBlock:^{
        NSLog(@"下载3------%@", [NSThread currentThread]);
    }];
    [op addExecutionBlock:^{
        NSLog(@"下载4------%@", [NSThread currentThread]);
    }];
    
    [op start];
}

NSInvocationOperation

Paste_Image.png

NSBlockOperation

Paste_Image.png

NSOperationQueue

Paste_Image.png

最大并发数

Paste_Image.png

队列的取消\恢复\暂停

Paste_Image.png

操作依赖

Paste_Image.png

操作监听

Paste_Image.png

自定义NSOperation

Paste_Image.png

自定义NSOperation图片下载思路--沙盒缓存

Paste_Image.png

自定义NSOperation图片下载思路--无沙盒缓存

Paste_Image.png

多图下载合成新图

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
    __block UIImage *image1 = nil;
    // 下载图片1
    NSBlockOperation *download1 = [NSBlockOperation blockOperationWithBlock:^{
        
        // 图片的网络路径
        NSURL *url = [NSURL URLWithString:@"http://img.pconline.com.cn/images/photoblog/9/9/8/1/9981681/200910/11/1255259355826.jpg"];
        
        // 加载图片
        NSData *data = [NSData dataWithContentsOfURL:url];
        
        // 生成图片
        image1 = [UIImage imageWithData:data];
    }];
    
    __block UIImage *image2 = nil;
    // 下载图片2
    NSBlockOperation *download2 = [NSBlockOperation blockOperationWithBlock:^{
        
        // 图片的网络路径
        NSURL *url = [NSURL URLWithString:@"http://pic38.nipic.com/20140228/5571398_215900721128_2.jpg"];

        
        // 加载图片
        NSData *data = [NSData dataWithContentsOfURL:url];
        
        // 生成图片
        image2 = [UIImage imageWithData:data];
    }];
    
    // 合成图片
    NSBlockOperation *combine = [NSBlockOperation blockOperationWithBlock:^{
        // 开启新的图形上下文
        UIGraphicsBeginImageContext(CGSizeMake(100, 100));
        
        // 绘制图片
        [image1 drawInRect:CGRectMake(0, 0, 50, 100)];
        image1 = nil;
        
        [image2 drawInRect:CGRectMake(50, 0, 50, 100)];
        image2 = nil;
        
        // 取得上下文中的图片
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        
        // 结束上下文
        UIGraphicsEndImageContext();
        
        // 回到主线程
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            self.imageView.image = image;
        }];
    }];
    [combine addDependency:download1];
    [combine addDependency:download2];
    
    [queue addOperation:download1];
    [queue addOperation:download2];
    [queue addOperation:combine];
}