GCD

最新推荐文章于 2025-01-07 19:51:09 发布

原创最新推荐文章于 2025-01-07 19:51:09 发布 · 442 阅读

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本文详细介绍了Grand Central Dispatch (GCD) 在iOS开发中的使用方法，包括串行和并发队列的概念、同步和异步任务的区别，以及如何利用GCD进行线程管理来提高应用程序的性能。

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GCD Demo

(void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

//同步和异步
//具备开辟线程的能力

//GCD 栈
//队列和任务

//A B

//串行队列
//dispatch_queue_create(const char *label, dispatch_queue_attr_t attr)

//并发队列
//dispatch_get_global_queue(long identifier, unsigned long flags)

//主队列
//dispatch_get_main_queue()

//同步任务基本不适用不会创建线程
//dispatch_sync(dispatch_queue_t queue, <#^(void)block#>)

//异步任务
//dispatch_async(<#dispatch_queue_t queue#>, <#^(void)block#>)
if 0
//同步串行
dispatch_queue_t queue = dispatch_queue_create(“abc”, nil);

//A
dispatch_sync(queue, ^{
NSLog(@”111%@”,[NSThread currentThread]);
});

//B
dispatch_sync(queue, ^{
NSLog(@”222%@”,[NSThread currentThread]);
});

//同步并发
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

//A
dispatch_sync(queue, ^{
NSLog(@”111%@”,[NSThread currentThread]);
});

//B
dispatch_sync(queue, ^{
NSLog(@”222%@”,[NSThread currentThread]);
});

endif

//异步串行  创建一个线程 执行多个任务
dispatch_queue_t queue1 = dispatch_queue_create("abc", nil);

dispatch_async(queue1, ^{
    NSInteger i = 0;
    while (i < 100) {
        NSLog(@"%ld",i++);
    }
    NSLog(@"111%@",[NSThread currentThread]);
});

dispatch_async(queue1, ^{
    NSInteger i = 999;
    while (i < 2000) {
        NSLog(@"%ld",i++);
    }
    NSLog(@"222%@",[NSThread currentThread]);
});

//异步并发  创建多个线程 执行多个任务
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_async(queue, ^{
    NSInteger i = 0;
    while (i < 100) {
        NSLog(@"%ld",i++);
    }
    NSLog(@"111%@",[NSThread currentThread]);
});

dispatch_async(queue, ^{
    NSInteger i = 999;
    while (i < 2000) {
        NSLog(@"%ld",i++);
    }
    NSLog(@"222%@",[NSThread currentThread]);
});

}

(void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

//单例
- (IBAction)clcik:(id)sender {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:@”https://ss2.baidu.com/6ONYsjip0QIZ8tyhnq/it/u=3200710946,482481474&fm=80“]];
//回到主线程刷新ui
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(@”%d”,[NSThread isMainThread]);
self.imageView.image = [UIImage imageWithData:data];
});
});
}

写一个单例

+(TQPerson *)sharedPerson
{
static TQPerson *p = nil;

static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
    p = [[TQPerson alloc] init];
});

return p;

}

GCD Group

(void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

if 0
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
dispatch_group_t group = dispatch_group_create();

//AF
//A  4
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

// dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(4 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
// NSLog(@”A 任务完成”);
// });
sleep(4);
NSLog(@”A 任务完成”);
});

//B  6
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

// dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(6 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
// NSLog(@”B 任务完成”);
// });
sleep(6);
NSLog(@”B 任务完成”);
});

dispatch_group_notify(group, dispatch_get_main_queue(), ^{
   [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
});

//
//dispatch_group_enter(dispatch_group_t group)  //retain +1
//dispatch_group_leave(dispatch_group_t group)  //release -1
//0

endif

[self testGroup];

}

-(void)testGroup
{
dispatch_group_t group = dispatch_group_create();

[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];

dispatch_group_enter(group); //+1

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(4 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
    dispatch_group_leave(group); //-1
    NSLog(@"123");
});

dispatch_group_enter(group);

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(6 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
    dispatch_group_leave(group); //-1
    NSLog(@"456");
});

dispatch_group_notify(group, dispatch_get_main_queue(), ^{
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
});

//AF

}