一、NSthread的初始化
1.动态方法
- (id)initWithTarget:(id)target selector:(SEL)selector object:(id)argument;
// 初始化线程
NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
// 设置线程的优先级(0.0 - 1.0，1.0最高级)
thread.threadPriority = 1;
// 开启线程
[thread start];
参数解析：
selector ：线程执行的方法，这个selector最多只能接收一个参数
target ：selector消息发送的对象
argument : 传给selector的唯一参数，也可以是nil
2.静态方法
+ (void)detachNewThreadSelector:(SEL)selector toTarget:(id)target withObject:(id)argument;
[NSThread detachNewThreadSelector:@selector(run) toTarget:self withObject:nil];
// 调用完毕后，会马上创建并开启新线程
3.隐式创建线程的方法
[self performSelectorInBackground:@selector(run) withObject:nil];
二、获取当前线程
NSThread *current = [NSThread currentThread];
三、获取主线程
NSThread *main = [NSThread mainThread];
四、暂停当前线程
// 暂停2s
[NSThread sleepForTimeInterval:2];
// 或者
NSDate *date = [NSDate dateWithTimeInterval:2 sinceDate:[NSDate date]];
[NSThread sleepUntilDate:date];
五、线程间的通信
1.在指定线程上执行操作
[self performSelector:@selector(run) onThread:thread withObject:nil waitUntilDone:YES];
2.在主线程上执行操作
[self performSelectorOnMainThread:@selector(run) withObject:nil waitUntilDone:YES];
3.在当前线程执行操作
[self performSelector:@selector(run) withObject:nil];
六、优缺点
1.优点：NSThread比其他两种多线程方案较轻量级，更直观地控制线程对象
2.缺点：需要自己管理线程的生命周期，线程同步。线程同步对数据的加锁会有一定的系统开销
七、下载图片的例子：
新建singeView app
新建项目，并在xib文件上放置一个imageView控件。按住control键拖到viewControll
er.h文件中创建imageView IBOutlet
ViewController.m中实现：
//
// ViewController.m
// NSThreadDemo
//
// Created by rongfzh on 12-9-23.
// Copyright (c) 2012年 rongfzh. All rights reserved.
//
#import "ViewController.h"
#define kURL @"http://avatar.csdn.net/2/C/D/1_totogo2010.jpg"
@interface ViewController ()
@end
@implementation ViewController
-(void)downloadImage:(NSString *) url{
NSData *data = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:url]];
UIImage *image = [[UIImage alloc]initWithData:data];
if(image == nil){
}else{
[self performSelectorOnMainThread:@selector(updateUI:) withObject:image waitUntilDone:YES];
}
}
-(void)updateUI:(UIImage*) image{
self.imageView.image = image;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// [NSThread detachNewThreadSelector:@selector(downloadImage:) toTarget:self withObject:kURL];
NSThread *thread = [[NSThread alloc]initWithTarget:self selector:@selector(downloadImage:) object:kURL];
[thread start];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
线程间通讯
线程下载完图片后怎么通知主线程更新界面呢？
[self performSelectorOnMainThread:@selector(updateUI:) withObject:image waitUntilDone:YES];
performSelectorOnMainThread是NSObject的方法，除了可以更新主线程的数据外，还可以更新其他线程的比如：
用：
performSelector:onThread:withObject:waitUntilDone:
运行下载图片：
图片下载下来了。
