iOS多线程

iOS多线程实现方案

多线程实现方案.png

GCD(Grand Central Dispatch)

一、基本用法
GCD会自动利用更多的CPU内核(比如双核、四核)。
GCD会自动管理线程的生命周期(创建线程、调度任务、销毁线程)。
只需要告诉GCD想要执行什么任务,不需要编写任何线程管理代码。

01 异步函数+并发队列:开启多条线程,并发执行任务 //start end...在多条线程
02 异步函数+串行队列:开启一条线程,串行执行任务//start end...为串行队列开启一个线程
03 同步函数+并发队列:不开线程,串行执行任务 //start...end在当前线程 
04 同步函数+串行队列:不开线程,串行执行任务//start...end在当前线程 
05 异步函数+主队列:不开线程,在主线程中串行执行任务//start end...主队列:在主线程执行
06 同步函数+主队列:不开线程,串行执行任务(注意死锁发生)
07 使用sync函数往当前串行队列中添加任务,会卡住当前的(线程.)串行队列
GCD.png
  • 例子: 异步+串行队列
NSLog(@"----start-%@" , [NSThread currentThread]);
dispatch_queue_t queue1 =  dispatch_queue_create("download1", DISPATCH_QUEUE_SERIAL);
dispatch_queue_t queue2 =  dispatch_queue_create("queue2", DISPATCH_QUEUE_SERIAL);

dispatch_async(queue2, ^{
          NSLog(@"---queue2222---%@",[NSThread currentThread]);
      });
dispatch_async(queue1, ^{
    NSLog(@"---download1---%@",[NSThread currentThread]);
});
dispatch_async(dispatch_get_main_queue(), ^{
    NSLog(@"---download2---%@",[NSThread currentThread]);
});
dispatch_async(queue1, ^{
    NSLog(@"---download3---%@",[NSThread currentThread]);
});
dispatch_async(queue1, ^{
    NSLog(@"---download4---%@",[NSThread currentThread]);
});
NSLog(@"----end-%@", [NSThread currentThread]);
//----start-{number = 1, name = main}
//----end-{number = 1, name = main}
//---download1---{number = 6, name = (null)}
//---queue2222---{number = 5, name = (null)}
//---download3---{number = 6, name = (null)}
//---download2---{number = 1, name = main}
//---download4---{number = 6, name = (null)}
  • 例子2:死锁
//使用sync往主队列加任务并不一定死锁。
//在子线程的当前串行队列继续加任务也会死锁。
dispatch_async(dispatch_queue_create("q", DISPATCH_QUEUE_SERIAL), ^{
        NSLog(@"-----%@",[NSThread currentThread]);
        dispatch_sync(dispatch_get_main_queue(), ^{
            NSLog(@"不会死锁===%@",[NSThread currentThread]);
        });
        dispatch_sync(dispatch_get_current_queue(), ^{
             NSLog(@"会死锁-----%@",[NSThread currentThread]);
        });
    });
 //-----{number = 6, name = (null)}
 //不会死锁==={number = 1, name = main}
//卡死

二、其他方法

  • dispatch_group_t队列组 dispatch_group_async dispatch_group_notify
    只能保证执行当前线程任务完成后notify,不能保证二级任务
dispatch_group_t group = dispatch_group_create();
dispatch_queue_t q = dispatch_get_global_queue(0, 0); 
dispatch_group_async(group, q, ^{
          for(NSInteger i = 0; i < 100; i++)
          {
              NSLog(@"++++%ld", (long)i);
          }
        
        dispatch_async(q, ^{

            for(NSInteger i = 0; i < 200; i++)
            {
                NSLog(@"-----%ld", (long)i);
            }
        });
  });
 dispatch_group_notify(group, q, ^{
        NSLog(@"======");
  });
//++++99
//-----0
//======
//-----1
  • dispatch_group_enter dispatch_group_leave 可以保证子任务
dispatch_group_t group = dispatch_group_create();
    
    dispatch_group_enter(group);
      for(NSInteger i = 0; i < 100; i++)
      {
          NSLog(@"++++%ld", (long)i);
      }
    dispatch_group_leave(group);

    dispatch_group_enter(group);
    dispatch_async(dispatch_get_global_queue(0, 0), ^{

        for(NSInteger i = 0; i < 200; i++)
        {
            NSLog(@"-----%ld", (long)i);
        }
        dispatch_group_leave(group);//写在async函数里才可
    });
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"======");
    });
  • dispatch_barrier_async栅栏函数,用来控制并发队列的执行顺序
  • dispatch_after延迟执行
//表名2秒钟之后调用run
//    [self performSelector:@selector(run) withObject:nil afterDelay:2.0];
//    [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(run) userInfo:nil repeats:YES];
    /*
     第一个参数:延迟时间
     第二个参数:要执行的代码
     */
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_global_queue(0, 0), ^{
        NSLog(@"---%@",[NSThread currentThread]);
    });
  • dispatch_once_t整个程序运行后只执行一次
static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{   
    });
  • dispatch_apply创建多条线程执行
//创建队列(并发队列)
dispatch_queue_t queue = dispatch_queue_create("com.downloadqueue", DISPATCH_QUEUE_CONCURRENT);
/*
 第一个参数:迭代的次数
 第二个参数:在哪个队列中执行
 第三个参数:block要执行的任务
 */
dispatch_apply(10, queue, ^(size_t index) {
    NSLog(@"%zd--%@",index,[NSThread currentThread]);
});

//文件在哪个地方(文件夹)
NSString *form = @"/Users/xiaomage/Desktop/form";
//要剪切到什么地方
NSString *to = @"/Users/xiaomage/Desktop/to";
NSFileManager *manager = [NSFileManager defaultManager];
NSArray *subpaths =  [manager subpathsAtPath:form];
//NSDirectoryEnumerator *enumer = [manager enumeratorAtPath:to];//可以打印嵌套文件夹下文件路径
//NSDirectoryEnumerator *enumer = [manager contentsOfDirectoryAtPath:to error:nil]; 
//for (NSDirectoryEnumerator *en in enumer) {
//        NSLog(@"%@",en);
//  }
//    NSLog(@"%@",subpaths);
NSInteger count = [subpaths count];
for (NSInteger i = 0; i]
    NSString *subpath = subpaths[i];
    NSString *fullPath = [form stringByAppendingPathComponent:subpath];
    //拼接目标文件全路径
    NSString *fileName = [to stringByAppendingPathComponent:subpath];
    //剪切操作
    [manager moveItemAtPath:fullPath toPath:fileName error:nil];
    NSLog(@"%@--%@",fullPath,fileName);
}

NSOperationQueue

一、NSOperation

  • NSInvocationOperation
 /*
     第一个参数:目标对象
     第二个参数:选择器,要调用的方法
     第三个参数:方法要传递的参数
     */
    //    NSInvocationOperation *op  = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(download) object:nil];
    //
    //    //启动操作
    //    [op start];
  • NSBlockOperation
 //1.封装操作//在主线程
    NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
        NSLog(@"1------%@",[NSThread currentThread]);
    }];
    
//2.追加操作//在子线程中并发执行
    [op1 addExecutionBlock:^{
        NSLog(@"2------%@",[NSThread currentThread]);
    }];
    [op1 addExecutionBlock:^{
        NSLog(@"3------%@",[NSThread currentThread]);
    }];
  • 写一个类继承NSOperation,重新main方法。[op start];时调用main方法。

二、 NSOperationQueue

1.将操作放入,系统自动异步执行
  • NSInvocationOperation添加到操作队列
/*
 主队列:凡是放到主队列里面的任务都在主线程执行[NSOperationQueue mainQueue]
 非主队列:alloc int,同时具备了并发和串行的功能,默认是并发队列
 */
//1.创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc]init];
//2.封装操作
NSInvocationOperation *op1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(download1) object:nil];
NSInvocationOperation *op2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(download2) object:nil];
NSInvocationOperation *op3 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(download3) object:nil];

//3.添加操作到队列,系统自动异步执行
[queue addOperation:op1];   //[op1 start]
[queue addOperation:op2];
[queue addOperation:op3];

-(void)download1
{
    NSLog(@"download1---%@",[NSThread currentThread]);
}
  • NSBlockOperation添加到操作队列
 //1.创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc]init];
//2.封装操作
NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"1----%@",[NSThread currentThread]);
}];
NSBlockOperation *op2 = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"2----%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
    NSLog(@"3----%@",[NSThread currentThread]);
}];
//3.添加操作到队列
[queue addOperation:op1];   //[op1 start]
[queue addOperation:op2];
//简便方法
[queue addOperationWithBlock:^{
     NSLog(@"4----%@",[NSThread currentThread]);
}];
  • 继承类类型
//1.创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc]init];
//2.封装操作
XMGOperation *op1 = [[XMGOperation alloc]init];
XMGOperation *op2 = [[XMGOperation alloc]init];
//3.添加操作到队列
[queue addOperation:op1];   //[op1 start]
[queue addOperation:op2];
2.其他
  • maxConcurrentOperationCount
    默认是最大并发数-1是并发队列,如果最大并发数>1,并发
    如果最大并发数==1,串行队列(也可能有多个线程)
  • suspended YES暂停NO恢复
    只能暂停队列中后面的操作,不能暂停正在执行的操作。
  • cancelAllOperations 取消,不再执行 operation.isCancelled判断操作是否已取消
  • 操作监听和依赖
//1.创建队列
NSOperationQueue *queue = [[NSOperationQueue alloc]init];
NSOperationQueue *queue1 = [[NSOperationQueue alloc]init];
//2.封装操作
NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"1----%@",[NSThread currentThread]);
}];
NSBlockOperation *op2 = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"2----%@",[NSThread currentThread]);
}];
NSBlockOperation *op3 = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"3----%@",[NSThread currentThread]);
}];
NSBlockOperation *op4 = [NSBlockOperation blockOperationWithBlock:^{
    NSLog(@"4----%@",[NSThread currentThread]);
}];
NSBlockOperation *op5 = [NSBlockOperation blockOperationWithBlock:^{
    for (NSInteger i=0; i<1000; i++) {
        NSLog(@"5-%zd---%@",i,[NSThread currentThread]);
    }
}];
op4.completionBlock = ^{
    NSLog(@"op4已经完成了---%@",[NSThread currentThread]);
};

//添加操作依赖,注意不能循环依赖
//也可以依赖其他队列的操作
[op1 addDependency:op5];
[op1 addDependency:op4];

//添加操作到队列
[queue addOperation:op1];
[queue addOperation:op2];
[queue addOperation:op3];
[queue addOperation:op4];
[queue1 addOperation:op5];
  • 线程间通信
//1.创建队列
NSOperationQueue *queue= [[NSOperationQueue alloc]init];
//2.下载图片
[queue addOperationWithBlock:^{
    //2.1.确定要下载网络图片的url地址,一个url唯一对应着网络上的一个资源
    NSURL *url = [NSURL URLWithString:@"http://p6.qhimg.com/t01d2954e2799c461ab.jpg"];
    //2.2.根据url地址下载图片数据到本地(二进制数据)
    NSData *data = [NSData dataWithContentsOfURL:url];
    //2.3.把下载到本地的二进制数据转换成图片
    UIImage *image = [UIImage imageWithData:data];
    //3.回到主线程刷新UI
    [[NSOperationQueue mainQueue] addOperationWithBlock:^{
        self.imageView.image = image;
        NSLog(@"%@----",[NSThread currentThread]);
    }];
}];

NSThread

/*
 第一个参数:目标对象
 第二个参数:选择器,调用哪个方法
 第三个参数:前面方法需要传递的参数
 */
NSThread *thread1 = [[NSThread alloc]initWithTarget:self selector:@selector(run) object:nil];
//设置基本属性
thread1.name = @"线程1";
//线程优先级
[thread1 setThreadPriority:1.0];//默认0.5,cpu调度线程的概率
//开启线程
[thread1 start];

 /*
     第一个参数:选择器,调用哪个方法
     第二个参数:目标对象
     第三个参数:前面方法需要传递的参数
  */
 [NSThread detachNewThreadSelector:@selector(run:) toTarget:self withObject:@"参数"];

/*
 第三种创建线程的方式
 特点:默认开启线程
 */
[self performSelectorInBackground:@selector(run:) withObject:@"后台线程"];

pthread了解

//创建线程
pthread_t thread;
/*
 第一个参数:线程对象
 第二个参数:线程属性
 第三个参数:void *(*)(void *) 指向函数的指针
 第四个参数:函数的参数
 */
pthread_create(&thread, NULL, run, NULL);

pthread_t thread1;
pthread_create(&thread1, NULL, run, NULL);

//void *(*)(void *)
void *run(void *param)
{
//    NSLog(@"---%@-",[NSThread currentThread]);
    for (NSInteger i =0 ; i<10000; i++) {
        NSLog(@"%zd--%@-",i,[NSThread currentThread]);
    }
    return NULL;
}

你可能感兴趣的:(iOS多线程)