IOS线程进阶

冷不防 2022-08-27 04:51 220阅读 0赞

# IOS线程学习 #

## NSThread创建 ##

### //类对象创建 ###

NSThread \* thread = \[\[ NSThread  alloc \]  initWithTarget : self  selector : @selector (first)  object : nil \];

\[thread start\];

//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