利用iphone的多线程实现“售票系统”(手把手教你iphone开发 - 基础篇)?
作者：孙东风?2009-11-10（请尊重作者劳动成果，转载务必注明出处）
?http://blog.csdn.net/dongfengsun/archive/2009/11/10/4794010.aspx
Java因为其本身支持多线程而给程序员带来很多方便，其实在iphone的开发中也支持多线程编程，并且一点也不比java麻烦。
在这篇文章中，笔者就拿大多数Java教程中经典的“售票系统多线程”作为实际例子，在iphone中进行同样的实现。
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下面是java版本的“售票系统多线程”代码：
package demo;??
?
public class SellTickets implements Runnable{??
???????
????private int tickets=100;??
??????
????public void run() {??
??????????
????????int count=0;??
??????????
????????while (true)??
????????{??
????????????//上锁??
????????????synchronized(this){??
????????????if (tickets>0){??
????????????????try {??
????????????????????Thread.sleep(500);??
????????????????} catch (InterruptedException e) {??
????????????????????e.printStackTrace();??
????????????????}??
????????????????count=100-tickets;??
????????????????System.out.println("当前票数是:"+tickets+"售出"+count??
????????????????????????+"线程名："+Thread.currentThread().getName());??
????????????????tickets--;??
????????????}else{??
????????????????break;??
????????????}??
????????????}??
????????}?????????
????}??
?
????public static void main(String[] args) {??
??????????
????????SellTickets r=new SellTickets();??
????????Thread t1=new Thread(r,"t1");??
????????t1.start();??
??????????
????????Thread t2=new Thread(r,"t2");??
????????t2.start();??
??????????
????????Thread t3=new Thread(r,"t3");??
????????t3.start();??
??????????
????????Thread t4=new Thread(r,"t4");??
????????t4.start();???????
????}??
}?
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以上java版本的代码执行后控制台输出如下：
当前票数是:100售出0线程名：t1
当前票数是:99售出1线程名：t2
当前票数是:98售出2线程名：t3
当前票数是:97售出3线程名：t4
当前票数是:96售出4线程名：t1
当前票数是:95售出5线程名：t2
当前票数是:94售出6线程名：t3
当前票数是:93售出7线程名：t4
当前票数是:92售出8线程名：t1
当前票数是:91售出9线程名：t2
当前票数是:90售出10线程名：t3
当前票数是:89售出11线程名：t4
当前票数是:88售出12线程名：t1
当前票数是:87售出13线程名：t2
当前票数是:86售出14线程名：t3
当前票数是:85售出15线程名：t4
当前票数是:84售出16线程名：t1
当前票数是:83售出17线程名：t2
当前票数是:82售出18线程名：t3
当前票数是:81售出19线程名：t4
当前票数是:80售出20线程名：t1
当前票数是:79售出21线程名：t2
当前票数是:78售出22线程名：t3
当前票数是:77售出23线程名：t4
当前票数是:76售出24线程名：t1
当前票数是:75售出25线程名：t2
当前票数是:74售出26线程名：t3
当前票数是:73售出27线程名：t4
……
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可以在iphone中进行同样的实现，Iphone的Frameworks/Foundation.framework框架支持多线程编程，接口定义在:
/Xcode3.1.4/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator3.1.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSThread.h
到相应的目录下打开此文件，可以看到绝大多数java中的接口这里也都能找到相应的实现，如下：
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/*??NSThread.h
????Copyright (c) 1994-2007, Apple Inc. All rights reserved.
*/
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#import <Foundation/NSObject.h>
#import <Foundation/NSDate.h>
?
@class NSArray, NSMutableDictionary, NSDate;
?
@interface NSThread : NSObject??{
@private
????id _private;
????uint8_t _bytes[44];
}
?
+ (NSThread *)currentThread;
?
+ (void)detachNewThreadSelector:(SEL)selector toTarget:(id)target withObject:(id)argument;
?
+ (BOOL)isMultiThreaded;
?
- (NSMutableDictionary *)threadDictionary;
?
+ (void)sleepUntilDate:(NSDate *)date;
+ (void)sleepForTimeInterval:(NSTimeInterval)ti;
?
+ (void)exit;
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#if MAC_OS_X_VERSION_10_2 <= MAC_OS_X_VERSION_MAX_ALLOWED
+ (double)threadPriority;
+ (BOOL)setThreadPriority:(double)p;
#endif
?
#if MAC_OS_X_VERSION_10_5 <= MAC_OS_X_VERSION_MAX_ALLOWED
?
+ (NSArray *)callStackReturnAddresses;
?
- (void)setName:(NSString *)n;
- (NSString *)name;
?
- (NSUInteger)stackSize;
- (void)setStackSize:(NSUInteger)s;
?
- (BOOL)isMainThread;
+ (BOOL)isMainThread; // reports whether current thread is main
+ (NSThread *)mainThread;
?
- (id)init;?// designated initializer
- (id)initWithTarget:(id)target selector:(SEL)selector object:(id)argument;
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- (BOOL)isExecuting;
- (BOOL)isFinished;
?
- (BOOL)isCancelled;
- (void)cancel;
?
- (void)start;
?
- (void)main;???// thread body method
?
#endif
?
@end
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FOUNDATION_EXPORT NSString * const NSWillBecomeMultiThreadedNotification;
FOUNDATION_EXPORT NSString * const NSDidBecomeSingleThreadedNotification;
FOUNDATION_EXPORT NSString * const NSThreadWillExitNotification;
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@interface NSObject (NSThreadPerformAdditions)
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#if MAC_OS_X_VERSION_10_2 <= MAC_OS_X_VERSION_MAX_ALLOWED
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait modes:(NSArray *)array;
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait;
????// equivalent to the first method with kCFRunLoopCommonModes
#endif
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#if MAC_OS_X_VERSION_10_5 <= MAC_OS_X_VERSION_MAX_ALLOWED
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(id)arg waitUntilDone:(BOOL)wait modes:(NSArray *)array;
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(id)arg waitUntilDone:(BOOL)wait;
????// equivalent to the first method with kCFRunLoopCommonModes
- (void)performSelectorInBackground:(SEL)aSelector withObject:(id)arg;
#endif
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@end
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从接口的定义中可以知道，NSThread和大多数iphone的接口对象一样，有两种方式可以初始化：
一种使用initWithTarget :(id)target selector:(SEL)selector object:(id)argument，但需要负责在对象的retain count为0时调用对象的release方法清理对象。
另一种则使用所谓的convenient method,这个方便接口就是detachNewThreadSelector，这个方法可以直接生成一个线程并启动它，而且无需为线程的清理负责。
因为在笔者的iphone版本“售票系统多线程”程序中需要设置线程的诸多参数，所以需要采用第一种方法来生成线程对象并自己启动它们。
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首先，新建一个“Window-based Application”项目，并命名为SellTickets，接下来在SellTicketsAppDelegate.h文件中声明以下变量：
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//
//??SellTicketsAppDelegate.h
//??SellTickets
//
//??Created by sun dfsun2009 on 09-11-10.
//??Copyright __MyCompanyName__ 2009. All rights reserved.
//
?
#import <UIKit/UIKit.h>
?
@interface SellTicketsAppDelegate : NSObject <UIApplicationDelegate> {
????int tickets;
????int count;
????NSThread* ticketsThreadone;
????NSThread* ticketsThreadtwo;
????UIWindow *window;
}
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@property (nonatomic, retain) IBOutlet UIWindow *window;
?
@end
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笔者在头文件中声明了两个NSThread的指针，下面需要在*.m文件中初始化并实现它们，如下：
//
//??SellTicketsAppDelegate.m
//??SellTickets
//
//??Created by sun dfsun2009 on 09-11-10.
//??Copyright __MyCompanyName__ 2009. All rights reserved.
//
?
#import "SellTicketsAppDelegate.h"
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@implementation SellTicketsAppDelegate
?
@synthesize window;
?
?
- (void)applicationDidFinishLaunching:(UIApplication *)application {
????tickets = 100;
????count = 0;
???
????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) {
?
????????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;
????????}
????}
}
?
-?????????(void)dealloc {
????[ticketsThreadone release];
????[ticketsThreadtwo release];
???
????[window release];
????[super dealloc];
}
?
@end
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笔者在实现中用alloc初始化了两个NSThread对象并分别把它们命名为“Thread-1”和“Thread-2”，运行程序可以看到如下输出：
[Session started at 2009-11-10 14:25:26 +0800.]
2009-11-10 14:25:28.814 SellTickets[1298:4103]?当前票数是:100,售出:0,线程名:Thread-1
2009-11-10 14:25:28.814 SellTickets[1298:4203]?当前票数是:100,售出:0,线程名:Thread-2
2009-11-10 14:25:29.316 SellTickets[1298:4103]?当前票数是:98,售出:2,线程名:Thread-1
2009-11-10 14:25:29.316 SellTickets[1298:4203]?当前票数是:98,售出:2,线程名:Thread-2
2009-11-10 14:25:29.817 SellTickets[1298:4103]?当前票数是:96,售出:4,线程名:Thread-1
2009-11-10 14:25:29.817 SellTickets[1298:4203]?当前票数是:96,售出:4,线程名:Thread-2
2009-11-10 14:25:30.318 SellTickets[1298:4103]?当前票数是:94,售出:6,线程名:Thread-1
2009-11-10 14:25:30.318 SellTickets[1298:4203]?当前票数是:94,售出:6,线程名:Thread-2
2009-11-10 14:25:30.819 SellTickets[1298:4103]?当前票数是:92,售出:8,线程名:Thread-1
2009-11-10 14:25:30.819 SellTickets[1298:4203]?当前票数是:92,售出:8,线程名:Thread-2
2009-11-10 14:25:31.320 SellTickets[1298:4103]?当前票数是:90,售出:10,线程名:Thread-1
2009-11-10 14:25:31.320 SellTickets[1298:4203]?当前票数是:90,售出:10,线程名:Thread-2
2009-11-10 14:25:31.820 SellTickets[1298:4103]?当前票数是:88,售出:12,线程名:Thread-1
2009-11-10 14:25:31.821 SellTickets[1298:4203]?当前票数是:87,售出:13,线程名:Thread-2
2009-11-10 14:25:32.321 SellTickets[1298:4103]?当前票数是:86,售出:14,线程名:Thread-1
2009-11-10 14:25:32.322 SellTickets[1298:4203]?当前票数是:86,售出:14,线程名:Thread-2
2009-11-10 14:25:32.823 SellTickets[1298:4103]?当前票数是:84,售出:16,线程名:Thread-1
2009-11-10 14:25:32.823 SellTickets[1298:4203]?当前票数是:83,售出:17,线程名:Thread-2
2009-11-10 14:25:33.323 SellTickets[1298:4103]?当前票数是:82,售出:18,线程名:Thread-1
2009-11-10 14:25:33.324 SellTickets[1298:4203]?当前票数是:81,售出:19,线程名:Thread-2
2009-11-10 14:25:33.824 SellTickets[1298:4103]?当前票数是:80,售出:20,线程名:Thread-1
2009-11-10 14:25:33.825 SellTickets[1298:4203]?当前票数是:79,售出:21,线程名:Thread-2
2009-11-10 14:25:34.325 SellTickets[1298:4103]?当前票数是:78,售出:22,线程名:Thread-1
2009-11-10 14:25:34.326 SellTickets[1298:4203]?当前票数是:77,售出:23,线程名:Thread-2
2009-11-10 14:25:34.826 SellTickets[1298:4103]?当前票数是:76,售出:24,线程名:Thread-1
2009-11-10 14:25:34.827 SellTickets[1298:4203]?当前票数是:75,售出:25,线程名:Thread-2
2009-11-10 14:25:35.327 SellTickets[1298:4103]?当前票数是:74,售出:26,线程名:Thread-1
2009-11-10 14:25:35.328 SellTickets[1298:4203]?当前票数是:73,售出:27,线程名:Thread-2
2009-11-10 14:25:35.827 SellTickets[1298:4103]?当前票数是:72,售出:28,线程名:Thread-1
2009-11-10 14:25:35.830 SellTickets[1298:4203]?当前票数是:71,售出:29,线程名:Thread-2
2009-11-10 14:25:36.329 SellTickets[1298:4103]?当前票数是:70,售出:30,线程名:Thread-1
2009-11-10 14:25:36.330 SellTickets[1298:4203]?当前票数是:69,售出:31,线程名:Thread-2
2009-11-10 14:25:36.830 SellTickets[1298:4103]?当前票数是:68,售出:32,线程名:Thread-1
2009-11-10 14:25:36.831 SellTickets[1298:4203]?当前票数是:67,售出:33,线程名:Thread-2
2009-11-10 14:25:37.331 SellTickets[1298:4103]?当前票数是:66,售出:34,线程名:Thread-1
2009-11-10 14:25:37.332 SellTickets[1298:4203]?当前票数是:65,售出:35,线程名:Thread-2
2009-11-10 14:25:37.832 SellTickets[1298:4103]?当前票数是:64,售出:36,线程名:Thread-1
2009-11-10 14:25:37.833 SellTickets[1298:4203]?当前票数是:63,售出:37,线程名:Thread-2
2009-11-10 14:25:38.333 SellTickets[1298:4103]?当前票数是:62,售出:38,线程名:Thread-1
2009-11-10 14:25:38.334 SellTickets[1298:4203]?当前票数是:61,售出:39,线程名:Thread-2
2009-11-10 14:25:38.834 SellTickets[1298:4103]?当前票数是:60,售出:40,线程名:Thread-1
2009-11-10 14:25:38.836 SellTickets[1298:4203]?当前票数是:59,售出:41,线程名:Thread-2
2009-11-10 14:25:39.335 SellTickets[1298:4103]?当前票数是:58,售出:42,线程名:Thread-1
2009-11-10 14:25:39.337 SellTickets[1298:4203]?当前票数是:58,售出:42,线程名:Thread-2
2009-11-10 14:25:39.838 SellTickets[1298:4103]?当前票数是:56,售出:44,线程名:Thread-1
2009-11-10 14:25:39.839 SellTickets[1298:4203]?当前票数是:55,售出:45,线程名:Thread-2
2009-11-10 14:25:40.339 SellTickets[1298:4103]?当前票数是:54,售出:46,线程名:Thread-1
2009-11-10 14:25:40.340 SellTickets[1298:4203]?当前票数是:53,售出:47,线程名:Thread-2
2009-11-10 14:25:40.840 SellTickets[1298:4103]?当前票数是:52,售出:48,线程名:Thread-1
2009-11-10 14:25:40.841 SellTickets[1298:4203]?当前票数是:51,售出:49,线程名:Thread-2
2009-11-10 14:25:41.341 SellTickets[1298:4103]?当前票数是:50,售出:50,线程名:Thread-1
2009-11-10 14:25:41.342 SellTickets[1298:4203]?当前票数是:49,售出:51,线程名:Thread-2
2009-11-10 14:25:41.842 SellTickets[1298:4103]?当前票数是:48,售出:52,线程名:Thread-1
2009-11-10 14:25:41.843 SellTickets[1298:4203]?当前票数是:47,售出:53,线程名:Thread-2
2009-11-10 14:25:42.343 SellTickets[1298:4103]?当前票数是:46,售出:54,线程名:Thread-1
2009-11-10 14:25:42.344 SellTickets[1298:4203]?当前票数是:45,售出:55,线程名:Thread-2
2009-11-10 14:25:42.844 SellTickets[1298:4103]?当前票数是:44,售出:56,线程名:Thread-1
2009-11-10 14:25:42.845 SellTickets[1298:4203]?当前票数是:43,售出:57,线程名:Thread-2
2009-11-10 14:25:43.345 SellTickets[1298:4103]?当前票数是:42,售出:58,线程名:Thread-1
2009-11-10 14:25:43.346 SellTickets[1298:4203]?当前票数是:42,售出:58,线程名:Thread-2
2009-11-10 14:25:43.846 SellTickets[1298:4103]?当前票数是:40,售出:60,线程名:Thread-1
2009-11-10 14:25:43.847 SellTickets[1298:4203]?当前票数是:39,售出:61,线程名:Thread-2
2009-11-10 14:25:44.347 SellTickets[1298:4103]?当前票数是:38,售出:62,线程名:Thread-1
2009-11-10 14:25:44.348 SellTickets[1298:4203]?当前票数是:37,售出:63,线程名:Thread-2
2009-11-10 14:25:44.848 SellTickets[1298:4103]?当前票数是:36,售出:64,线程名:Thread-1
2009-11-10 14:25:44.849 SellTickets[1298:4203]?当前票数是:35,售出:65,线程名:Thread-2
2009-11-10 14:25:45.349 SellTickets[1298:4103]?当前票数是:34,售出:66,线程名:Thread-1
2009-11-10 14:25:45.350 SellTickets[1298:4203]?当前票数是:33,售出:67,线程名:Thread-2
2009-11-10 14:25:45.850 SellTickets[1298:4103]?当前票数是:32,售出:68,线程名:Thread-1
2009-11-10 14:25:45.851 SellTickets[1298:4203]?当前票数是:31,售出:69,线程名:Thread-2
2009-11-10 14:25:46.350 SellTickets[1298:4103]?当前票数是:30,售出:70,线程名:Thread-1
2009-11-10 14:25:46.351 SellTickets[1298:4203]?当前票数是:29,售出:71,线程名:Thread-2
2009-11-10 14:25:46.851 SellTickets[1298:4103]?当前票数是:28,售出:72,线程名:Thread-1
2009-11-10 14:25:46.853 SellTickets[1298:4203]?当前票数是:27,售出:73,线程名:Thread-2
2009-11-10 14:25:47.352 SellTickets[1298:4103]?当前票数是:26,售出:74,线程名:Thread-1
2009-11-10 14:25:47.354 SellTickets[1298:4203]?当前票数是:25,售出:75,线程名:Thread-2
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可以看到，因为两个线程共享变量tickets和count，开头的输出就产生了异常情况，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，所以我们需要让代码成为线程安全的，修改头文件如下：
?
//
//??SellTicketsAppDelegate.h
//??SellTickets
//
//??Created by sun dfsun2009 on 09-11-10.
//??Copyright __MyCompanyName__ 2009. All rights reserved.
//
?
#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
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然后在实现中添加如下代码：
?
//
//??SellTicketsAppDelegate.m
//??SellTickets
//
//??Created by sun dfsun2009 on 09-11-10.
//??Copyright __MyCompanyName__ 2009. All rights reserved.
//
?
#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
?
最后千万别忘记在dealloc方法中调用对象的release进行资源释放，现在再次运行下看看，iphone版本的“售票系统多线程”程序是否跑起来了：）