【转】IOS里的多线程编程详解

柔光的暖阳◎ 2021-09-19 09:32 288阅读 0赞

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 \{  
 \[\_myCondition release\];  
    \[super dealloc\];  
\}

本文转自编程小翁博客园博客，原文链接：http://www.cnblogs.com/wengzilin/archive/2012/08/15/2639576.html，如需转载请自行联系原作者