本文来自简书，原文地址:http://www.jianshu.com/p/4ac227e763fa
GCD
Grand Central Dispatch (GCD) 是 Apple 开发的一个多核编程的解决方法。该方法在 Mac OS X 10.6 雪豹中首次推出，并随后被引入到了 iOS4.0 中。GCD 是一个替代诸如 NSThread, NSOperationQueue, NSInvocationOperation 等技术的很高效和强大的技术。 GCD 和 block 的配合使用，可以方便地进行多线程编程。
Clone
git clone https://github.com/KingComeFromChina/GCD.git
任务和队列
1.任务分为同步任务和异步任务，队列分为串行和并行 2.同步任务不会开线程，异步任务会开线程
- (
void)sync_queue:(
dispatch_queue_t)queue{
dispatch_sync(queue, ^{
NSLog(
@"同步1 - %@",[
NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(
@"同步2 - %@",[
NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(
@"同步3 - %@",[
NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(
@"同步4 - %@",[
NSThread currentThread]);
});
}
- (
void)async_queue:(
dispatch_queue_t)queue{
dispatch_async(queue, ^{
NSLog(
@"异步1 - %@",[
NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(
@"异步2 - %@",[
NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(
@"异步3 - %@",[
NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(
@"异步4 - %@",[
NSThread currentThread]);
});
}
3.串行队列一个一个的执行，并行队列一起执行
同步任务
dispatch_sync(<#dispatch_queue_t _Nonnull queue#>, <#^(void)block#>)
异步任务
dispatch_async(<#dispatch_queue_t _Nonnull queue#>, <#^(void)block#>)
主队列
dispatch_queue_t mainQueue = dispatch_get_main_queue();
全局并发队列
dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
自定义串行队列
dispatch_queue_t serialQueue = dispatch_queue_create("wanglei", NULL);
自定义并行队列
dispatch_queue_t concurrentQueue = dispatch_queue_create("king", DISPATCH_QUEUE_CONCURRENT);
同步主线程会卡死，造成死循环
[self sync_queue:mainQueue];
异步主线程不会开线程，顺序执行
[self async_queue:mainQueue];
同步全局并发不会开线程，顺序执行
[self sync_queue:globalQueue];
异步全局并发会开线程，乱序执行
[self async_queue:globalQueue];
同步串行不会开线程，顺序执行
[self sync_queue:serialQueue];
异步串行会开线程，顺序执行
[self async_queue:serialQueue];
同步并行不会开线程，顺序执行
[self sync_queue:concurrentQueue];
异步并行会开线程，乱序执行
[self async_queue:concurrentQueue];
线程间通信
#pragma mark - 线程间通讯
- (
void)threadCommunication{
dispatch_queue_t mainQueue = dispatch_get_main_queue();
dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,
0);
dispatch_async(globalQueue, ^{
NSURL *url = [
NSURL URLWithString:
@""];
NSData *data = [[
NSData alloc]initWithContentsOfURL:url];
NSLog(
@"%@",[
NSThread currentThread]);
dispatch_async(mainQueue, ^{
data;
NSLog(
@"mainQueue -- %@",[
NSThread currentThread]);
});
});
}
GCD创建单例
- (
void)touchesBegan:(
NSSet<
UITouch *> *)touches withEvent:(
UIEvent *)event{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
NSLog(
@"只执行一次");
});
}
GCD创建分组任务
- (
void)dispatch_group{
dispatch_group_t
group = dispatch_group_create();
dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,
0);
dispatch_group_async(
group, globalQueue, ^{
NSLog(@
"分组任务1");
});
dispatch_group_async(
group, globalQueue, ^{
NSLog(@
"分组任务2");
});
dispatch_group_notify(
group, globalQueue, ^{
NSLog(@
"上面分组任务完成后，才会执行");
});
}
GCD延迟操作
- (
void)dosomethingByTime{
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(
10 *
NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
NSLog(
@"延迟10s加载");
});
dispatch_queue_t concurrentQueue = dispatch_queue_create(
"wanglei", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(concurrentQueue, ^{
NSLog(
@"dispatch_async - 1-%@",[
NSThread currentThread]);
});
dispatch_async(concurrentQueue, ^{
NSLog(
@"dispatch_async - 2-%@",[
NSThread currentThread]);
});
dispatch_barrier_async(concurrentQueue, ^{
NSLog(
@"dispatch_barrier_async-%@",[
NSThread currentThread]);
});
dispatch_barrier_async(concurrentQueue, ^{
NSLog(
@"dispatch_barrier_async- 3 -%@",[
NSThread currentThread]);
});
dispatch_barrier_async(concurrentQueue, ^{
NSLog(
@"dispatch_barrier_async- 4 -%@",[
NSThread currentThread]);
});
}
GCD下载图片及合成
- (
void)drawRectImage{
dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,
0);
dispatch_async(globalQueue, ^{
NSURL *url1 = [
NSURL URLWithString:
@"http://pic6.huitu.com/res/20130116/84481_20130116142820494200_1.jpg"];
NSData *data1 = [
NSData dataWithContentsOfURL:url1];
UIImage *image1 = [
UIImage imageWithData:data1];
NSURL *url2 = [
NSURL URLWithString:
@"http://g.hiphotos.baidu.com/image/pic/item/c2cec3fdfc03924578c6cfe18394a4c27c1e25e8.jpg"];
NSData *data2 = [
NSData dataWithContentsOfURL:url2];
UIImage *image2 = [
UIImage imageWithData:data2];
UIGraphicsBeginImageContextWithOptions(image1.size,
NO,
0.0);
CGFloat image1Width = image1.size.width;
CGFloat image1Height = image1.size.height;
[image1 drawInRect:
CGRectMake(
0,
0, image1Width, image1Height)];
CGFloat image2Width = image2.size.width *
0.5;
CGFloat image2Height = image2.size.height *
0.5;
CGFloat image2Y = image1Height - image2Height;
[image2 drawInRect:
CGRectMake(
0, image2Y, image2Width, image2Height)];
UIImage *fullImage =
UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
dispatch_queue_t mainQueue = dispatch_get_main_queue();
dispatch_async(mainQueue, ^{
self.imageView.image = fullImage;
});
});
}
GCD实现的验证码倒计时
- (
void)btnClick{
[_btn setTitle:
@"重发(60s)" forState:
UIControlStateNormal];
__block
int timeout=
59;
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,
0);
dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,
0,
0,queue);
dispatch_source_set_timer(_timer,dispatch_walltime(
NULL,
0),
1.0*
NSEC_PER_SEC,
0);
dispatch_source_set_event_handler(_timer, ^{
if(timeout<=
0){
dispatch_source_cancel(_timer);
dispatch_async(dispatch_get_main_queue(), ^{
self.btn.userInteractionEnabled =
YES;
[
self.btn setTitle:
@"获取验证码" forState:
UIControlStateNormal];
});
}
else{
int seconds = timeout %
60;
NSString *strTime = [
NSString stringWithFormat:
@"%.2d", seconds];
dispatch_async(dispatch_get_main_queue(), ^{
[
UIView beginAnimations:
nil context:
nil];
[
UIView setAnimationDuration:
1];
[
self.btn setTitle:[
NSString stringWithFormat:
@"重发(%@秒)",strTime] forState:
UIControlStateNormal];
[
UIView commitAnimations];
self.btn.userInteractionEnabled =
NO;
});
timeout--;
}
});
dispatch_resume(_timer);
}
效果图
效果图
