4.4 GCD->3.0 其他用法
2016-04-18 本文已影响113人
蓝田_Loto
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本文相关目录：
==================== 所属文集：4.0 多线程 ====================
4.1 多线程基础->1.0 进程 & 线程
······················ 2.0 多线程简介
4.2 pthread
4.3 NSThread->1.0 创建线程
····················· 2.0 线程属性
····················· 3.0 线程状态/线程生命周期
····················· 4.0 多线程安全隐患
····················· 5.0 线程间通讯和常用方法
4.4 GCD->1.0 GCD简介和使用
·············· 2.0 线程间的通信
·············· 3.0 其他用法
·············· 4.0 GCD 的定时器事件
4.5 NSOperation->1.0 NSOperation简介
························ 2.0 NSOperationQueue
························ 3.0 线程间通信
························ 4.0 自定义NSOperation
4.6 RunLoop - 运行循环
===================== 所属文集：4.0 多线程 =====================
3.1 barrier函数
作用：控制多线程的执行顺序
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
// 这里使用全局并发队列的方式会导致 dispatch_barrier_async 功能失效
dispatch_queue_t queue =
dispatch_queue_create("TD", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
NSLog(@"----1-----%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"----2-----%@", [NSThread currentThread]);
});
dispatch_barrier_async(queue, ^{
NSLog(@"----barrier-----%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"----3-----%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"----4-----%@", [NSThread currentThread]);
});
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
打印结果：
其他用法 - barrier函数[1419:94670] ----2-----<NSThread: 0x7fc4a0c2c5d0>{number = 3, name = (null)}
其他用法- barrier函数[1419:94732] ----1-----<NSThread: 0x7fc4a0f0cb20>{number = 2, name = (null)}
其他用法- barrier函数[1419:94732] ----barrier-----<NSThread: 0x7fc4a0f0cb20>{number = 2, name = (null)}
其他用法- barrier函数[1419:94732] ----3-----<NSThread: 0x7fc4a0f0cb20>{number = 2, name = (null)}
其他用法 - barrier函数[1419:94670] ----4-----<NSThread: 0x7fc4a0c2c5d0>{number = 3, name = (null)}
3.2 延迟执行
方法1：调用NSObject的方法
// 该方法在那个线程调用，那么run就在哪个线程执行（当前线程），通常是主线程
// 2秒后再调用self的run方法
[selfperformSelector:@selector(run) withObject:nilafterDelay:2.0];
方法2：使用GCD函数
// 这里是在主线程执行，如果想要在子线程执行，选择相应的队列
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
// 2秒后异步执行这里的代码...
});
方法3：使用NSTimer
[NSTimer scheduledTimerWithTimeInterval:2.0
target:self
selector:@selector(run)
userInfo:nil
repeats:NO];
代码示例：
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
[self delay1];
}
#pragma mark - 方法1：调用NSObject的方法
- (void)delay1 {
NSLog(@"touchesBegan-----");
// 2秒后再调用self的run方法
[self performSelector:@selector(run) withObject:nil afterDelay:2.0];
}
#pragma mark - 方法2：使用 GCD 函数
- (void)delay2 {
NSLog(@"touchesBegan-----");
// 这里是在主线程执行，如果想要在子线程执行，选择相应的队列
dispatch_after(
dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)),
dispatch_get_main_queue(), ^{
NSLog(@"run-----");
});
}
#pragma mark - 方法3：使用NSTimer定时器
- (void)delay3 {
NSLog(@"touchesBegan-----");
[NSTimer scheduledTimerWithTimeInterval:2.0
target:self
selector:@selector(run)
userInfo:nil
repeats:NO];
}
- (void)run {
NSLog(@"run-----");
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
打印结果：
其他用法 - 延迟执行[1651:114465] touchesBegan-----
其他用法 - 延迟执行[1651:114465] run-----
3.3 一次性代码
使用dispatch_once 函数能保证某段代码在程序运行过程中只被执行1次，适合做资源的加载
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
// 只执行1次的代码(这里面默认是线程安全的)
});
}
3.4 快速迭代
使用dispatch_apply函数能进行快速迭代遍历：
dispatch_apply(<#size_t iterations#>, <#dispatch_queue_t queue#>, ^(size_t) {
// 代码
});
dispatch_apply(10, dispatch_get_global_queue(0, 0), ^(size_t index){
// 执行10次代码，index顺序不确定
});
代码示例：文件剪切
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
[self apply];
}
#pragma mark - 文件剪切方法1：快速迭代
- (void)apply {
dispatch_queue_t queue =
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
NSString *from = @"/Users/TD/Desktop/From";
NSString *to = @"/Users/TD/Desktop/To";
NSFileManager *mgr = [NSFileManager defaultManager];
NSArray *subpaths = [mgr subpathsAtPath:from];
dispatch_apply(subpaths.count, queue, ^(size_t index) {
NSString *subpath = subpaths[index];
NSString *fromFullpath = [from stringByAppendingPathComponent:subpath];
NSString *toFullpath = [to stringByAppendingPathComponent:subpath];
// 剪切
[mgr moveItemAtPath:fromFullpath toPath:toFullpath error:nil];
NSLog(@"%@---%@", [NSThread currentThread], subpath);
});
}
#pragma mark - 文件剪切方法2：传统方式
- (void)moveFile {
NSString *from = @"/Users/TD/Desktop/From";
NSString *to = @"/Users/TD/Desktop/To";
NSFileManager *mgr = [NSFileManager defaultManager];
//获取文件夹下的所有文件路径，包括子文件夹下的文件路径
NSArray *subpaths = [mgr subpathsAtPath:from];
for (NSString *subpath in subpaths) {
//全路径
NSString *fromFullpath = [from stringByAppendingPathComponent:subpath];
NSString *toFullpath = [to stringByAppendingPathComponent:subpath];
dispatch_async(
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// 剪切
[mgr moveItemAtPath:fromFullpath toPath:toFullpath error:nil];
});
}
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
3.5 队列组/调度组
有这么一种需求：
首先：分别异步执行2个耗时的操作
其次：等2个异步操作都执行完毕后，再回到主线程执行操作
解决办法：用队列组，也叫做调度组
// 创建一个队列组
dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// 执行1个耗时的异步操作
});
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// 执行1个耗时的异步操作
});
dispatch_group_notify(group, dispatch_get_main_queue(),
^{
// 等前面的异步操作都执行完毕后，回到主线程...
});
代码结构：
其他用法 - 队列组调度组.png
代码示例：
#import "ViewController.h"
@interface ViewController ()
@property(weak, nonatomic) IBOutlet UIImageView *imageView;
@property(nonatomic, strong) UIImage *image1; //图片1
@property(nonatomic, strong) UIImage *image2; //图片2
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
dispatch_queue_t queue =
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
// 创建一个队列组
dispatch_group_t group = dispatch_group_create();
// 1.下载图片1
dispatch_group_async(group, queue, ^{
// 图片的网络路径
NSURL *url = [NSURL URLWithString:@"http://img.pconline.com.cn/images/photoblog/9/9/8/1/9981681/200910/11/1255259355826.jpg"];
// 加载图片
NSData *data = [NSData dataWithContentsOfURL:url];
// 生成图片
self.image1 = [UIImage imageWithData:data];
});
// 2.下载图片2
dispatch_group_async(group, queue, ^{
// 图片的网络路径
NSURL *url = [NSURL URLWithString: @"http://pic38.nipic.com/20140228/5571398_215900721128_2.jpg"];
// 加载图片
NSData *data = [NSData dataWithContentsOfURL:url];
// 生成图片
self.image2 = [UIImage imageWithData:data];
});
// 3.将图片1、图片2合成一张新的图片（也可以直接在此处回到主线程，只不过是因为绘制图片比较耗时，没有放在主线程而已）
dispatch_group_notify(group, queue, ^{
// 开启新的图形上下文
UIGraphicsBeginImageContext(CGSizeMake(100, 100));
// 绘制图片
[self.image1 drawInRect:CGRectMake(0, 0, 50, 100)];
[self.image2 drawInRect:CGRectMake(50, 0, 50, 100)];
// 取得上下文中的图片
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
// 结束上下文
UIGraphicsEndImageContext();
// 回到主线程显示图片
dispatch_async(dispatch_get_main_queue(), ^{
// 4.将新图片显示出来
self.imageView.image = image;
});
});
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
本文源码 Demo 详见 Github
https://github.com/shorfng/iOS_4.0_multithreading.git
作者：蓝田（Loto）
出处： 简书
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