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];
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];
[self performSelectorOnMainThread:@selector(run) withObject:nil waitUntilDone:YES];
[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
[self performSelectorOnMainThread:@selector(updateUI:) withObject:image waitUntilDone:YES];
performSelector:onThread:withObject:waitUntilDone:
图片下载下来了。
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