iPhone多线程是本文要介绍的内容,多线程在各种编程语言中都是难点,很多语言中实现起来很麻烦,objective-c虽然源于c,但其多线程编程却相当简单,可以与java相媲美。这篇文章主要从线程创建与启动、线程的同步与锁、线程的交互、线程池等等四个方面简单的讲解一下iphone中的多线程编程。
一、线程创建与启动
线程创建主要有二种方式:
- - (id)init; // designated initializer
- - (id)initWithTarget:(id)target selector:(SEL)selector object:(id)argument;
当然,还有一种比较特殊,就是使用所谓的convenient method,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。这个方法的接口是:
- + (void)detachNewThreadSelector:(SEL)aSelector toTarget:(id)aTarget withObject:(id)anArgument
前两种方法创建后,需要手机启动,启动的方法是:
- - (void)start;
二、线程的同步与锁
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。这是来源于网上的一个例子:
- SellTicketsAppDelegate.h 文件
- // 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
- SellTicketsAppDelegate.m 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
三、线程的交互
线程在运行过程中,可能需要与其它线程进行通信,如在主线程中修改界面等等,可以使用如下接口:
- - (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait
由于在本过程中,可能需要释放一些资源,则需要使用NSAutoreleasePool来进行管理,如:
- - (void)startTheBackgroundJob {
- NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
- // to do something in your thread job
- ...
- [self performSelectorOnMainThread:@selector(makeMyProgressBarMoving) withObject:nil waitUntilDone:NO];
- [pool release];
- }
小结:剖析iPhone多线程的内容介绍完了,希望本文对你有所帮助!
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