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iphone ios 多线程 multi thread编程汇总

2011-10-07 15:34 309 查看
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老规矩,先贴2篇e文的官方文章

1)Threading Programming Guide
http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/Multithreading/CreatingThreads/CreatingThreads.html#//apple_ref/doc/uid/10000057i-CH15-SW7
2)Concurrency(并发) Programming Guide
http://developer.apple.com/library/ios/#documentation/General/Conceptual/ConcurrencyProgrammingGuide/ConcurrencyandApplicationDesign/ConcurrencyandApplicationDesign.html#//apple_ref/doc/uid/TP40008091-CH100-SW6
这两个有区别,如果各位e文好,又有耐心,就滤过下面的。

推荐

1)[Cocoa]深入浅出 Cocoa 之多线程 NSThread
http://blog.csdn.net/kesalin/article/details/6698146
2)利用iphone的多线程实现“售票系统”(手把手教你iphone开发 - 基础篇)
http://blog.csdn.net/dongfengsun/article/details/4794010
3)Concurrency 学习 (Mac & iphone) (一)
http://hi.baidu.com/songxiaoweiss/blog/item/699971d7c6c579de50da4b51.html
4)Concurrency 学习 (Mac & iphone) (二)
http://hi.baidu.com/songxiaoweiss/blog/item/82b08d13912cb4dca6ef3f29.html
找了很多网上关于ios多线程编码的文章,基本都是说到3个方法

1)detachNewThreadSelector或performSelectorInBackground

// NSThread中的方法,启动线程Detaches a new thread and uses the specified selector as the thread entry point.
+ (void)detachNewThreadSelector:(SEL)aSelector toTarget:(id)aTarget withObject:(id)anArgument
// NSObject中的方法,启动线程Invokes a method of the receiver on a new background thread.
- (void)performSelectorInBackground:(SEL)aSelector withObject:(id)arg
// NSObject中的方法,因为更新UI只能是主线程中执行。所以这个函数主要用于子线程调用主线程中的aSelector,来更新主线程的UI或参数。
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait


很经典的例子,主线程要更新列表图像,需要连接网络下载:

[1]主线程调用

[NSThread detachNewThreadSelector:@selector(downloadimg:) toTarget:self withObject:url];


[2]线程下载完毕后,通知主线程,并更新列表图像。

[self performSelectorOnMainThread:@selector(stateIsLoading) withObject:nil waitUntilDone:NO];


2)常规军,NSThread

- (id)init;	// designated initializer
- (id)initWithTarget:(id)target selector:(SEL)selector object:(id)argument;


这个例子我copy自网上,要说明线程的同步与锁,最好的例子可能就是多个窗口同时售票的售票系统了。我们知道在java中,使用synchronized来同步,而iphone虽然没有提供类似java下的synchronized关键字,但提供了NSCondition对象接口。查看NSCondition的接口说明可以看出,NSCondition是iphone下的锁对象,所以我们可以使用NSCondition实现iphone中的线程安全。

//  SellTicketsAppDelegate.h
import <UIKit/UIKit.h>

@interface SellTicketsAppDelegate : NSObject <UIApplicationDelegate> {
int tickets;
int count;
NSThread* ticketsThreadone;
NSThread* ticketsThreadtwo;
NSCondition* ticketsCondition;
UIWindow *window;
}
@property (nonatomic, retain) IBOutlet UIWindow *window;
@end


实现文件

//  SellTicketsAppDelegate.m
import "SellTicketsAppDelegate.h"

@implementation SellTicketsAppDelegate
@synthesize window;

- (void)applicationDidFinishLaunching:(UIApplication *)application {
tickets = 100;
count = 0;
// 锁对象
ticketCondition = [[NSCondition alloc] init];
ticketsThreadone = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
[ticketsThreadone setName:@"Thread-1"];
[ticketsThreadone start];

ticketsThreadtwo = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
[ticketsThreadtwo setName:@"Thread-2"];
[ticketsThreadtwo start];
//[NSThread detachNewThreadSelector:@selector(run) toTarget:self withObject:nil];
// Override point for customization after application launch
[window makeKeyAndVisible];

}

- (void)run{
while (TRUE) {
// 上锁
[ticketsCondition lock];
if(tickets > 0){
[NSThread sleepForTimeInterval:0.5];
count = 100 - tickets;
NSLog(@"当前票数是:%d,售出:%d,线程名:%@",tickets,count,[[NSThread currentThread] name]);
tickets--;
}else{
break;
}
[ticketsCondition unlock];
}
}

- (void)dealloc {
[ticketsThreadone release];
[ticketsThreadtwo release];
[ticketsCondition release];
[window release];
[super dealloc];
}
@end


注意,线程initWithTarget初始化完毕后,要调用start来启动他。

“这两种方式的区别是:前一种一调用就会立即创建一个线程来做事情;而后一种虽然你 alloc 了也 init了,但是要直到我们手动调用 start 启动线程时才会真正去创建线程。这种延迟实现思想在很多跟资源相关的地方都有用到。后一种方式我们还可以在启动线程之前,对线程进行配置,比如设置 stack
大小,线程优先级。”

3)线程队列NSOperationQueue

可以参考文章使用NSOperationQueue简化多线程开发
http://marshal.easymorse.com/archives/4519
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