1.多线程的简单认知

1.进程和线程的认知

进程：一个正在运行的程序就是一个进程一个进程由一个或多个线程组成进程只负责资源的调度分配，线程才是真正的执行单元

线程

//当我们应用程序刚刚运行的时候，系统会自动为我们开放一个线程，这个线程叫做主线程

//子线程:程序员用代码手动开启的线程

//子线程存在的意义：执行耗时操作的任务

//子线程在执行完自己的任务之后会自动销毁

2.创建线程

第一种

-(void)createNSThread

{

//创建一个线程###

NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(haoshicaozuo) object:@"123"];

thread.name = @"这是一个线程";

[thread start];

//NSLog(@"%@",thread);

NSLog(@"%@",[NSThread mainThread]);//打印当前应用程序的主线程

NSLog(@"%@",[NSThread currentThread]);//当前线程

NSLog(@"%d",[NSThread isMainThread]); //判断是否为主线程

}

第二种

-(void)createNSThread1

{

//快捷创建无返回值

[NSThread detachNewThreadSelector:@selector(haoshicaozuo) toTarget:self withObject:@"456"];

}

第三种

-(void)createNSThread2

{

//隐式开启线程

[NSThread cancelPreviousPerformRequestsWithTarget:self selector:@selector(haoshicaozuo) object:@"789"];

}

2.NSOperation

/NSOperation 是一个抽象类，我们一般不直接使用它，而是使用它的子类NSInvocationOperation 类还有NSBlockOperation

//如果他们单独使用都是在主线程执行，只有和队列放在一起才是在子线程下执行的

-(void)createNSOperation

{

NSInvocationOperation *operation1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(operationAction1) object:nil];

//[operation1 start];

NSInvocationOperation *operation2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(operationAction2) object:

nil];

NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{

for (int i = 20 ; i < 30 ; i++) {

NSLog(@"%d",i);

}}];

//操作队列

//目的：是将我们的任务放在一个队列中执行

//任务：任务执行在主线程还是在子线程全都是由我们的队列来决定的

//加入到队列

//mainQueue 代表主队列

//如果 alloc init 的就代表其他队列

// NSOperationQueue *queue = [NSOperationQueue mainQueue];

NSOperationQueue *queue = [[NSOperationQueue alloc] init] ;

//先加的先执行，后加的后执行，但执行的时间不一定可能后边的现执行完

[queue addOperation:operation1];

[queue addOperation:operation2];

[queue addOperation:operation3];

}

-(void)operationAction2

{

NSLog(@"%d",[NSThread isMainThread]);

}

-(void)operationAction1

{

NSLog(@"%d",[NSThread isMainThread]);

}

3.GCD

在了解GCD之前我们应该先了解几个基础概念

异步：不再一个线程执行

同步：在同一个线程执行

串行：按顺序串在一起执行

并行：一起执行

#pragma --------- 同步主队列 ------------

//同步不能加主队列所以这个是错的，仅仅是看个模式

-(void)createScyMain

{

//获得主队列(主队列也是一个串行队列)

dispatch_queue_t queue = dispatch_get_main_queue();

//将任务加到队列中

//第一个参数：放队列的

//第二个参数：要执行的任务

dispatch_sync(queue, ^{

NSLog(@"1.......%@",[NSThread currentThread]);

});

dispatch_sync(queue, ^{

NSLog(@"2.......%@",[NSThread currentThread]);

});

dispatch_sync(queue, ^{

NSLog(@"3.......%@",[NSThread currentThread]);

});

}

#pragma --------- 异步主队列 ------------

//不开辟线程，就在主线程执行

-(void)createAsycnMain

{

//获得主队列(主队列也是一个串行队列)

dispatch_queue_t queue = dispatch_get_main_queue();

dispatch_async(queue, ^{

NSLog(@"1..........%@",[NSThread currentThread]);

});

dispatch_async(queue, ^{

NSLog(@"2..........%@",[NSThread currentThread]);

});

dispatch_async(queue, ^{

NSLog(@"3..........%@",[NSThread currentThread]);

});

}

#pragma --------- 同步串行队列 ------------

//不具备开启线程的能力，在当前线程完成任务

-(void)createSyncSerial

{

//创建串行队列

dispatch_queue_t queue = dispatch_queue_create("aaa.com", DISPATCH_QUEUE_SERIAL);

dispatch_sync(queue, ^{

NSLog(@"1........%@",[NSThread currentThread]);

});

dispatch_sync(queue, ^{

NSLog(@"2........%@",[NSThread currentThread]);

});

dispatch_sync(queue, ^{

NSLog(@"3........%@",[NSThread currentThread]);

});

}

#pragma --------- 异步串行队列 ------------

//具备开启线程的能力，但是任务是串行的

-(void)createAsyncSerial

{

dispatch_queue_t queue = dispatch_queue_create("aaa.com", DISPATCH_QUEUE_SERIAL);

dispatch_async(queue, ^{

NSLog(@"1........%@",[NSThread currentThread]);

});

dispatch_async(queue, ^{

NSLog(@"2.......%@",[NSThread currentThread]);

});

dispatch_async(queue, ^{

NSLog(@"3........%@",[NSThread currentThread]);

});

}

#pragma --------- 同步并行队列 ------------

//不具备开启线程的能力，其实同步的都在主线程，主线程没有串行队列，所以并行的功能就没有用了

-(void)createSyncConcurrent

{

//创建一个并发队列

//第一个参数队列的名字

//第二个参数类型

//我们自己创建的并发队列

// dispatch_queue_t queue = dispatch_queue_create("sb.com", DISPATCH_QUEUE_CONCURRENT);

//获得全局的并发队列

//第一个参数是优先级，默认的就行了

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_sync(queue, ^{

NSLog(@"1.........%@",[NSThread currentThread]);

});

dispatch_sync(queue, ^{

NSLog(@"2.........%@",[NSThread currentThread]);

});

dispatch_sync(queue, ^{

NSLog(@"3.........%@",[NSThread currentThread]);

});

}

#pragma --------- 异步并行队列 ------------

//最经常使用的就是这个

//异步具备开启子线程的能力，并且并行执行任务

-(void)createAsynConcurrent

{

//获得全局的并发队列

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_async(queue, ^{

NSLog(@"1.......%@",[NSThread currentThread]);

});

dispatch_async(queue, ^{

NSLog(@"2.......%@",[NSThread currentThread]);

});

dispatch_async(queue, ^{

NSLog(@"3.......%@",[NSThread currentThread]);

});

NSLog(@"大傻逼");

}

4-GCD网络请求的应用

以请求一张图片为例我们在ViewController的viewDidLoad里面要写上如下代码

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

//创建全局的并发队列

dispatch_queue_t queue = dispatch_queue_create("aaa", DISPATCH_QUEUE_CONCURRENT);

dispatch_async(queue, ^{

NSURL *url = [NSURL URLWithString: @"https://ss0.bdstatic.com/94oJfD_bAAcT8t7mm9GUKT-xh_/timg?image&quality=100&size=b4000_4000&sec=1464140268&di=6b6b2e3ea5da34b7da1e02fd28c7acd2&src=http://pic36.nipic.com/20131115/12106414_153522431000_2.jpg"];

NSData *data = [NSData dataWithContentsOfURL:url];

dispatch_async(dispatch_get_main_queue(), ^{

//UI层的东西只有回到主线程里才能设置

self.imgView.image = [UIImage imageWithData:data];

});

});

}

5-GCD函数的使用

延时执行

-(void)creatAfter

{

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{

NSLog(@"%@",[NSThread currentThread]);

NSLog(@"皮卡皮卡，皮卡丘");

});

}

快速遍历

-(void)rapidTeaverse

{

for (int i = 0; i < 10; i++) {

NSLog(@"%d",i);

}

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_apply(10, queue, ^(size_t index) {

NSLog(@"%zd %@",index,[NSThread currentThread]);

});

}

组队列

-(void)creatGroup

{

//获取并行队列

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

//创建一个组队列

dispatch_group_t group = dispatch_group_create();

//下载图片1

dispatch_group_async(group, queue, ^{

NSURL *url = [NSURL URLWithString:@"https://ss0.bdstatic.com/94oJfD_bAAcT8t7mm9GUKT-xh_/timg?image&quality=100&size=b4000_4000&sec=1464231860&di=33256b2f206f8082ad634b5250a2b39d&src=http://www.benbenla.cn/images/20120330/benbenla-04b.jpg"];

NSData *data = [NSData dataWithContentsOfURL:url];

self.image1 = [UIImage imageWithData:data];

});

dispatch_group_async(group, queue, ^{

NSURL *url = [NSURL URLWithString:@"http://www.deskcar.com/desktop/fengjing/200895150214/21.jpg"];

NSData *data = [NSData dataWithContentsOfURL:url];

self.image2 = [UIImage imageWithData:data];

});

//将图片1和2组合在一起

dispatch_group_notify(group, queue, ^{

//开启一个新的图片上下文

UIGraphicsBeginImageContext(CGSizeMake(375, 667));

//绘制图片

[self.image1 drawInRect:CGRectMake(0, 0, 375/2, 667)];

[self.image2 drawInRect:CGRectMake(375/2, 0, 375/2, 667)];

//取得图片上下文中的图片

UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

//结束图片上下文

UIGraphicsEndImageContext();

dispatch_async(dispatch_get_main_queue(), ^{

self.imgV.image = image;

});

});

}

iOS多线程概述

iOS多线程概述

1.多线程的简单认知

1.进程和线程的认知

2.创建线程

2.NSOperation

3.GCD

4-GCD网络请求的应用

5-GCD函数的使用

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