传智播客学习笔记 网络多线程
主线程处理UI，避免耗时操作
iOS多线程技术有4种
pthread，通用技术，跨平台 c语言，程序员管理生命周期，几乎不用
NSThread 面向对象，可以直接操作线程 OC语言 程序员 管理生命周期，偶尔使用
GCD 替代NSThread，可以利用多核性能 c语言 自动管理 经常使用
NSOperation 基于GCD，更加面向对象，多了功能 OC语言 自动管理 经常使用
GCD
获得主队列
// 1.获得主队列 dispatch_queue_t queue = dispatch_get_main_queue();
获得全局并发队列
// 1.获得全局的并发队列 dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
GCD其他用法
dispatch_once
dispatch_after
dispatch_group_async\dispatch_group_notify
异步函数，串行队列
/**
* 用dispatch_async异步函数往串行队列中添加任务
*/
- (void)asyncSerialQueue
{
// 1.创建串行队列
dispatch_queue_t queue = dispatch_queue_create("com.itheima.queue", NULL);
// 2.添加任务到队列中 执行
dispatch_async(queue, ^{
NSLog(@"----下载图片1-----%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"----下载图片2-----%@", [NSThread currentThread]);
});
dispatch_async(queue, ^{
NSLog(@"----下载图片3-----%@", [NSThread currentThread]);
});
// 总结: 只开1个线程执行任务
}
异步函数，并发队列
/**
* 用dispatch_sync同步函数往并发队列中添加任务
*/
- (void)syncGlobalQueue
{
// 1.获得全局的并发队列
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
// 2.添加任务到队列中 执行
dispatch_sync(queue, ^{
NSLog(@"----下载图片1-----%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"----下载图片2-----%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"----下载图片3-----%@", [NSThread currentThread]);
});
// 总结: 不会开启新的线程, 并发队列失去了并发的功能
}
同步函数，串行队列
/**
* 用dispatch_sync同步函数往串行列中添加任务
*/
- (void)syncSerialQueue
{
// 1.创建串行队列
dispatch_queue_t queue = dispatch_queue_create("com.itheima.queue", NULL);
// 2.添加任务到队列中 执行
dispatch_sync(queue, ^{
NSLog(@"----下载图片1-----%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"----下载图片2-----%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"----下载图片3-----%@", [NSThread currentThread]);
});
// 3.释放资源
// dispatch_release(queue); // MRC(非ARC)
// 总结: 不会开启新的线程
}
同步函数，串行队列
/**
* 用dispatch_sync同步函数往串行列中添加任务
*/
- (void)syncSerialQueue
{
// 1.创建串行队列
dispatch_queue_t queue = dispatch_queue_create("com.itheima.queue", NULL);
// 2.添加任务到队列中 执行
dispatch_sync(queue, ^{
NSLog(@"----下载图片1-----%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"----下载图片2-----%@", [NSThread currentThread]);
});
dispatch_sync(queue, ^{
NSLog(@"----下载图片3-----%@", [NSThread currentThread]);
});
// 总结: 不会开启新的线程
}
GCD一个例子
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{
NSLog(@"--download--%@", [NSThread currentThread]);
// 下载图片
NSURL *url = [NSURL URLWithString:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];
NSData *data = [NSData dataWithContentsOfURL:url]; // 这行会比较耗时
UIImage *image = [UIImage imageWithData:data];
// 回到主线程显示图片
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(@"--imageView--%@", [NSThread currentThread]);
self.imageView.image = image;
});
});
GCD多个任务构建一个组
完成2个图片的下载以后，进行合并处理
//定义宏简化调用
#define global_queue dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
#define main_queue dispatch_get_main_queue()
// 创建一个组
dispatch_group_t group = dispatch_group_create();
// 开启一个任务下载图片1
__block UIImage *image1 = nil;
dispatch_group_async(group, global_queue, ^{
image1 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];
});
// 开启一个任务下载图片2
__block UIImage *image2 = nil;
dispatch_group_async(group, global_queue, ^{
image2 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg"];
});
// 同时执行下载图片1\下载图片2操作
// 等group中的所有任务都执行完毕, 再回到主线程执行其他操作
dispatch_group_notify(group, main_queue, ^{
self.imageView1.image = image1;
self.imageView2.image = image2;
// 合并
UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 100), NO, 0.0);
[image1 drawInRect:CGRectMake(0, 0, 100, 100)];
[image2 drawInRect:CGRectMake(100, 0, 100, 100)];
self.bigImageView.image = UIGraphicsGetImageFromCurrentImageContext();
// 关闭上下文
UIGraphicsEndImageContext();
});
NSThread
初始化调用
self.thread = [[NSThread alloc] initWithTarget:self selector:@selector(test) object:nil]; self.thread.name = @"线程A"; [self.thread start];
隐式调用
[self performSelectorInBackground:@selector(download) withObject:nil];
回到主线程
下面选一个就行了
// 2.回到主线程显示图片 [self.imageView performSelector:@selector(setImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:NO]; // setImage: 1s [self.imageView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:NO]; [self performSelectorOnMainThread:@selector(settingImage:) withObject:image waitUntilDone:NO];
线程同步使用互斥锁（移动端并不适合处理这个问题，建议由服务器执行）
解决多个线程同时改变同一个变量的时候的资源抢夺问题，然后变量的数值会不正确
@synchronized
- (void)viewDidLoad
{
[super viewDidLoad];
// 默认有100张
self.leftTicketsCount = 100;
// 开启多条线程同时卖票
self.thread0 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];
self.thread0.name = @"售票员 A";
// self.thread0.threadPriority = 0.0;
self.thread1 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];
self.thread1.name = @"售票员 B";
// self.thread1.threadPriority = 1.0;
self.thread2 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];
self.thread2.name = @"售票员 C";
// self.thread2.threadPriority = 0.0;
}
/**
* 卖票
*/
- (void)saleTicket
{
while (1) {
@synchronized(self) { // 加锁(只能用一把锁)
// 1.先检查票数
int count = self.leftTicketsCount;
if (count > 0) {
// 暂停
// [NSThread sleepForTimeInterval:0.0002];
// 2.票数 - 1
self.leftTicketsCount = count - 1;
NSThread *current = [NSThread currentThread];
NSLog(@"%@ 卖了一张票, 剩余%d张票", current.name, self.leftTicketsCount);
} else {
// 退出线程
[NSThread exit];
}
} // 解锁
}
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
[self.thread0 start];
[self.thread1 start];
[self.thread2 start];
}
NSOperation
创建operation
NSInvocationOperation *operation1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download) object:nil];
NSBlockOperation *operation2 = [[NSBlockOperation alloc] init];
[operation2 addExecutionBlock:^{
NSLog(@"NSBlockOperation------下载图片1---%@", [NSThread currentThread]);
}];
NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
for (int i = 0; i < 10; i++) {
NSLog(@"NSBlockOperation------下载图片---%@", [NSThread currentThread]);
[NSThread sleepForTimeInterval:0.1];
}
}];
添加到队列
// 2.创建队列 NSOperationQueue *queue = [[NSOperationQueue alloc] init]; queue.maxConcurrentOperationCount = 2; // 2 ~ 3为宜 // 设置依赖 [operation2 addDependency:operation3]; [operation3 addDependency:operation1]; // 3.添加操作到队列中(自动执行操作, 自动开启线程) [queue addOperation:operation1]; [queue addOperation:operation2]; [queue addOperation:operation3];
设计一个子类继承自NSOperation
//头文件设计 #import <Foundation/Foundation.h> @class HMDownloadOperation; //设置代理 @protocol HMDownloadOperationDelegate <NSObject> @optional - (void)downloadOperation:(HMDownloadOperation *)operation didFinishDownload:(UIImage *)image; @end @interface HMDownloadOperation : NSOperation @property (nonatomic, copy) NSString *url; @property (nonatomic, strong) NSIndexPath *indexPath; @property (nonatomic, weak) id<HMDownloadOperationDelegate> delegate; @end
实现文件
主要需要实现main方法，然后在主线程中将处理结果返回给代理
#import "HMDownloadOperation.h"
@implementation HMDownloadOperation
/**
* 在main方法中实现具体操作
*/
- (void)main
{
@autoreleasepool {
NSURL *downloadUrl = [NSURL URLWithString:self.url];
NSData *data = [NSData dataWithContentsOfURL:downloadUrl]; // 这行会比较耗时
UIImage *image = [UIImage imageWithData:data];
if ([self.delegate respondsToSelector:@selector(downloadOperation:didFinishDownload:)]) {
dispatch_async(dispatch_get_main_queue(), ^{ // 回到主线程, 传递图片数据给代理对象
[self.delegate downloadOperation:self didFinishDownload:image];
});
}
}
}
@end