多线程NSOperation的使用

 1 //创建线程队列
 2     NSOperationQueue *queue = [[NSOperationQueue alloc]init];
 3     
 4     //关闭暂停队列，用于让所有的线程加入队列后在执行任务
 5     [queue setSuspended:YES];
 6     
 7     //设置最大并发数，
 8     queue.maxConcurrentOperationCount = 2;
 9     
10     //创建线程
11     NSInvocationOperation *operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(operation1:)  object:@"operation1"];
12     
13     //设置线程优先级
14     operation1.queuePriority = NSOperationQueuePriorityNormal;
15     
16     //创建第二个线程
17     NSInvocationOperation *operation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(operation2:) object:@"operation2"];
18     //设置线程优先级
19     operation2.queuePriority = NSOperationQueuePriorityVeryHigh;
20     
21     //将线程加入队列
22     [queue addOperation:operation1];
23     [queue addOperation:operation2];
24     
25     
26     //用Block创建多线程
27     
28     [queue addOperationWithBlock:^{
29     
30       //注意这里我们要将任务放进自动释放池，因为这段代码不在（主线程）中
31         @autoreleasepool {
32             
33             for (int i = 0; i < 10; i ++) {
34                 
35                 NSLog(@"operation3%d",i);
36             }
37         }
38     }];
39     
40     
41     //开始队列
42     [queue setSuspended:NO];

#import "UIImageView+cache.h"

@implementation UIImageView (cache)

- (void)setImages:(NSString *)str
{
    //创建队列
    NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    
    //设置最大并发
    queue.maxConcurrentOperationCount = 1;
    //创建线程
    NSInvocationOperation *operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(operationAction:) object:str];
    
    //将线程加入线程队列
    [queue addOperation:operation];
    
    
}

- (void)operationAction:(NSString *)str
{
    NSURL *url = [NSURL URLWithString:str];
    
    NSData *data = [NSData dataWithContentsOfURL:url];
    
    //在这里我们要修改UI了所以要重新回到主线程
    //第一种回主线程的方式
    [self performSelectorOnMainThread:@selector(setImage:) withObject:[UIImage imageWithData:data] waitUntilDone:YES];
    /*
     //第二种方式回到主线程
     
     [[NSOperationQueue mainQueue] addOperationWithBlock:^{
     
     self.image = [UIImage imageWithData:data];
     
     }];

     */
    
}



@end

viewController中的代码：
#import "ViewController.h"
#import "UIImageView+cache.h"
@interface ViewController ()

@property (nonatomic, strong)NSMutableArray *dataArr;

@end

@implementation ViewController

- (NSMutableArray *)dataArr
{
    if (_dataArr == nil) {
        _dataArr = [NSMutableArray array];
        
        return _dataArr;
    }
    
    return _dataArr;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
    
    for (int i = 0; i < 8; i ++) {
        for (int j = 0; j < 6; j ++) {
            
            UIImageView *imageview = [[UIImageView alloc]initWithFrame:CGRectMake(j * 64, i * 80, 60, 75)];
            imageview.backgroundColor = [UIColor yellowColor];
            
            [self.view addSubview:imageview];
            
            [self.dataArr addObject:imageview];
            
        }
    }
    
}
- (IBAction)click:(UIButton *)sender {
    
    for (UIImageView *imageview in self.dataArr) {
        

        [imageview setImages:@"http://img31.mtime.cn/pi/2013/03/08/144644.81111130_1280X720.jpg"];
        
    }
}


@end
这样就解决了主线程阻塞的问题。