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）

 

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。

 

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();       

    }  

} 

 

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

……

 

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：

 

/*  NSThread.h

    Copyright (c) 1994-2007, Apple Inc. All rights reserved.

*/

 

#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;

 

#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;

 

- (BOOL)isExecuting;

- (BOOL)isFinished;

 

- (BOOL)isCancelled;

- (void)cancel;

 

- (void)start;

 

- (void)main;   // thread body method

 

#endif

 

@end

 

FOUNDATION_EXPORT NSString * const NSWillBecomeMultiThreadedNotification;

FOUNDATION_EXPORT NSString * const NSDidBecomeSingleThreadedNotification;

FOUNDATION_EXPORT NSString * const NSThreadWillExitNotification;

 

@interface NSObject (NSThreadPerformAdditions)

 

#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

 

#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

 

@end

 

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。

 

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：

 

//

//  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;

}

 

@property (nonatomic, retain) IBOutlet UIWindow *window;

 

@end

 

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"

 

@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

 

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

 

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

 

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：）