IOS线程进阶

IOS线程学习

NSThread创建

//类对象创建

NSThread* thread = [[NSThreadalloc]initWithTarget:selfselector:@selector(first)object:nil];

    [threadstart];

2

//类加方法直接创建

    [NSThreaddetachNewThreadSelector:@selector(second)toTarget:selfwithObject:nil];

    [selfperformSelectorInBackground:@selector(third)withObject:nil];

3系统方法

  [selfperformSelectorOnMainThread:@selector(func)withObject:nilwaitUntilDone:NO];

二.多线程进阶

NSOperation&NSOperationQueue

很多时候我们使用多线程，需要控制线程的并发数，毕竟线程也是消耗系统资源的，当程序中同时运行的线程过多时，系统必然变慢。 所以很多时候我们会控制同时运行线程的数目。

NSOperation可以封装我们的操作，然后将创建好的NSOperation对象放到NSOperationQueue中，OperationQueue便开始启动新的线程去执行队列中的操作，OperationQueue的并发度是可以通过如下方式进行设置:

- (void)setMaxConcurrentOperationCount:(NSInteger)count 
- (void)operation{
    //操作队列
    NSOperationQueue *queue=[[NSOperationQueue alloc]init];
    //最大并行数量
    queue.maxConcurrentOperationCount=3;
    for (int i=1; i<11; i++) {
        MyOperation *operation=[[MyOperation alloc]init];
        operation.time=i;
        //添加到队列
        [queue addOperation:operation];
        [operation release];
    }
}
#import <Foundation/Foundation.h>
@interface MyOperation : NSOperation
@property (nonatomic, assign)int time;
@end
#import "MyOperation.h"
@implementation MyOperation
//
- (void)main{
    
    sleep(self.time);
    NSLog(@"%d",self.time);
}
@end

GCD

GCD是Grand Central Dispatch的缩写，是一系列的BSD层面的接口，在Mac 10.6 和iOS4.0以后才引入的，且现在NSOperation和NSOperationQueue的多线程的实现就是基于GCD的。目前这个特性也被移植到 FreeBSD上了，可以查看libdispatch这个开源项目。

比如一个在UIImageView中显示一个比较大的图片

#import "ViewController.h"
@implementation ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];
    UIButton* button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(100, 230, 100, 30);
    [button setTitle:@"标题" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonClick) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
    
    _imageView = [[UIImageView alloc] initWithFrame:CGRectMake(110, 10, 100, 200)];
    [self.view addSubview:_imageView];
}
- (void)buttonClick{
    //[self gcd];
    //[self gcdGroup];
    
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        NSURL* url = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/news/pic/item/f3d3572c11dfa9ecde69b09e60d0f703908fc1f0.jpg"];
        NSData* data = [NSData dataWithContentsOfURL:url];
        NSLog(@"下载完成");
        UIImage* image = [UIImage imageWithData:data];
        //主线程
        dispatch_async(dispatch_get_main_queue(), ^{
            _imageView.image = image;
        });
    });
}
- (void)gcdGroup{
    //创建组
    dispatch_group_t t = dispatch_group_create();
    dispatch_group_async(t, dispatch_get_global_queue(0, 0), ^{
        [self first];
    });
    dispatch_group_async(t, dispatch_get_global_queue(0, 0), ^{
        [self second];
    });
    dispatch_group_async(t, dispatch_get_global_queue(0, 0), ^{
        [self third];
    });
    dispatch_group_notify(t, dispatch_get_global_queue(0, 0), ^{
        NSLog(@"执行完成");
    });
}
- (void)gcd{
    dispatch_queue_t t = dispatch_queue_create(NULL, NULL);
    //想成在t线程里执行block里面的语句
    dispatch_async(t, ^{
        [self first];
    });
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [self second];
    });
}
- (void)first{
    sleep(1);
    NSLog(@"1");
}
- (void)second{
    sleep(2);
    NSLog(@"2");
}
- (void)third{
    sleep(3);
    NSLog(@"3");
}
@end