iphone开发之多线程NSThread和NSInvocationOperation

以下是开发初期收集整理的一点资料 

多线程之NSInvocationOperation

多线程编程是防止主线程堵塞，增加运行效率等等的最佳方法。而原始的多线程方法存在很多的毛病，包括线程锁死等。在Cocoa中，Apple提供了NSOperation这个类，提供了一个优秀的多线程编程方法。

本次介绍NSOperation的子集，简易方法的NSInvocationOperation：

@implementation MyCustomClass

 - (void)launchTaskWithData:(id)data

{

    //创建一个NSInvocationOperation对象，并初始化到方法

    //在这里，selector参数后的值是你想在另外一个线程中运行的方法（函数，Method）

    //在这里，object后的值是想传递给前面方法的数据

    NSInvocationOperation* theOp = [[NSInvocationOperation alloc] initWithTarget:self

                    selector:@selector(myTaskMethod:) object:data];

 

    // 下面将我们建立的操作“Operation”加入到本地程序的共享队列中（加入后方法就会立刻被执行）

    // 更多的时候是由我们自己建立“操作”队列

    [[MyAppDelegate sharedOperationQueue] addOperation:theOp];

}

 

// 这个是真正运行在另外一个线程的“方法”

- (void)myTaskMethod:(id)data

{

    // Perform the task.

}

 

@end一个NSOperationQueue 操作队列，就相当于一个线程管理器，而非一个线程。因为你可以设置这个线程管理器内可以并行运行的的线程数量等等。下面是建立并初始化一个操作队列：

@interface MyViewController : UIViewController {

 

    NSOperationQueue *operationQueue;

    //在头文件中声明该队列

}

@end

 

@implementation MyViewController

 

- (id)init 

{

    self = [super init];

    if (self) {

        operationQueue = [[NSOperationQueue alloc] init]; //初始化操作队列

        [operationQueue setMaxConcurrentOperationCount:1];

        //在这里限定了该队列只同时运行一个线程

        //这个队列已经可以使用了

    }

    return self;

}

 

- (void)dealloc

{

    [operationQueue release];

    //正如Alan经常说的，我们是程序的好公民，需要释放内存！

    [super dealloc];

}

 

@end简单介绍之后，其实可以发现这种方法是非常简单的。很多的时候我们使用多线程仅仅是为了防止主线程堵塞，而NSInvocationOperation就是最简单的多线程编程，在iPhone编程中是经常被用到的。

///////////////////////////////////////////////////////////////////////////////////////////////////

1 在主线程里加入一个loading画面……

2 {

3 [window addSubview:view_loading];

4 [NSThread detachNewThreadSelector:@selector(init_backup:) toTarget:self withObject:nil];

5 }

可以通过performSelectorOhMainThread更新UI元素，比如设置进度条等等。最后消除loading画面，载入主View。

7 - (void)init_backup:(id)sender

8 {

9 NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

10

11 // ...

12 int i = status;

13 [self performSelectorOnMainThread:@selector(show_loading:) withObject:[NSNumber numberWithInt:i] waitUntil Done:NO];

14

15 [view_loading removeFromSuperview];

16 [window addSubview:tabcontroller_main.view];

17 [pool release];

18 }

 

///////////////////////////////////////////////////////

利用iphone的多线程实现和线程同步

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。

#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

-------------------------------------------------------------------------------------

// 定义

#import <UIKit/UIKit.h>

@interface ThreadSyncSampleViewController : UIViewController {

 int _threadCount;

 NSCondition *_myCondition;

}

@end

//实现文件如下:

#import "ThreadSyncSampleViewController.h"

@implementation ThreadSyncSampleViewController

 

/*

// The designated initializer. Override to perform setup that is required before the view is loaded.

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {

    if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {

        // Custom initialization

    }

    return self;

}

*/

/*

// Implement loadView to create a view hierarchy programmatically, without using a nib.

- (void)loadView {

}

*/

 

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.

- (void)viewDidLoad {

    [super viewDidLoad];

 //

 //_myCondition = nil;

 //

 _myCondition = [[NSCondition alloc] init];

 //

 NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:30

             target:self

              selector:@selector(threadTester)

              userInfo:nil

             repeats:YES];

 [timer fire];

 

}

- (void)threadTester{

 [_myCondition lock];

 

 _threadCount = -2;

 //如果有n个要等待的thread，这里置成 -n

 [_myCondition unlock];

 //

 NSLog(@"");

 NSLog(@"------------------------------------------------------------------------------");

 [NSThread detachNewThreadSelector:@selector(threadOne) toTarget:self withObject:nil];

 [NSThread detachNewThreadSelector:@selector(threadTwo) toTarget:self withObject:nil];

 [NSThread detachNewThreadSelector:@selector(threadThree) toTarget:self withObject:nil];

 return;

}

- (void)threadOne{

 NSLog(@"@@@ In thread 111111 start.");

 [_myCondition lock];

 

 int n = rand()%5 + 1;

 NSLog(@"@@@ Thread 111111 Will sleep %d seconds ,now _threadCount is : %d",n,_threadCount);

 sleep(n);

 //[NSThread sleepForTimeInterval:n];

 _threadCount ++ ;

 NSLog(@"@@@ Thread 111111 has sleep %d seconds ,now _threadCount is : %d",n,_threadCount);

 [_myCondition signal];

 NSLog(@"@@@ Thread 1111111 has signaled ,now _threadCount is : %d",_threadCount);

 [_myCondition unlock];

 NSLog(@"@@@ In thread one complete.");

 [NSThread exit];

 return;

}

- (void)threadTwo{

 NSLog(@"### In thread 2222222 start.");

 [_myCondition lock];

 

 int n = rand()%5 + 1;

 NSLog(@"### Thread 2222222 Will sleep %d seconds ,now _threadCount is : %d",n,_threadCount);

 sleep(n);

 //   [NSThread sleepForTimeInterval:n];

 _threadCount ++ ;

 NSLog(@"### Thread 2222222 has sleep %d seconds ,now _threadCount is : %d",n,_threadCount);

 [_myCondition signal];

 NSLog(@"### Thread 2222222 has signaled ,now _threadCount is : %d",_threadCount);

 [_myCondition unlock];

 //_threadCount ++ ;

 NSLog(@"### In thread 2222222 complete.");

 [NSThread exit];

 return;

}

- (void)threadThree{

 NSLog(@"<<< In thread 333333 start.");

 [_myCondition lock];

 while (_threadCount < 0) {

  [_myCondition wait];

 }

 NSLog(@"<<< In thread 333333 ,_threadCount now is %d ,will start work.",_threadCount);

 [_myCondition unlock];

 NSLog(@"<<< In thread 333333 complete.");

 [NSThread exit];

 return;

}

/*

// Override to allow orientations other than the default portrait orientation.

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {

    // Return YES for supported orientations

    return (interfaceOrientation == UIInterfaceOrientationPortrait);

}

*/

- (void)didReceiveMemoryWarning {

 // Releases the view if it doesn't have a superview.

    [super didReceiveMemoryWarning];

 

 // Release any cached data, images, etc that aren't in use.

}

- (void)viewDidUnload {

 // Release any retained subviews of the main view.

 // e.g. self.myOutlet = nil;

}

- (void)dealloc {

 [_myCondition release];

    [super dealloc];

}

@end