ios开发多线程篇——线程间的通信

一.简单说明
线程间通信：在一个进程中，线程往往不是孤立存在的，多个线程之间需要经常进行通信。
线程间通信的体现：
一个线程传递数据给另一个线程。
在一个线程中执行完特定任务后，转到另一个线程继续执行任务。

线程间通信常用方法
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait;
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(id)arg waitUntilDone:(BOOL)wait;
线程间通信示例－图片下载

代码一：

#import "ViewController.h"

@interface ViewController ()

@property(nonatomic,strong) UIImageView *iconView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.iconView = [[UIImageView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    [self.view addSubview:self.iconView];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)download{
    //从网络中下载图片
    NSURL *url = [NSURL URLWithString:@"http://banbao.chazidian.com/uploadfile/2016-01-25/s145368924044608.jpg"];
    //把图片转换成二进制的数据
    NSData *data = [NSData dataWithContentsOfURL:url];
    //把数据转换成图片
    UIImage *image = [UIImage imageWithData:data];
    //回到主线程中设置图片
    [self performSelectorOnMainThread:@selector(settingImage:)
                           withObject:image
                        waitUntilDone:NO];
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

    //在子线程中调用download方法下载图片
    [self performSelectorInBackground:@selector(download) withObject:nil];
}

- (void)settingImage:(UIImage *)image{
    self.iconView.image = image;
}

@end

代码二

#import "ViewController.h"

@interface ViewController ()

@property(nonatomic,strong) UIImageView *iconView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.iconView = [[UIImageView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    [self.view addSubview:self.iconView];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)download:(NSString *)title{
    NSLog(@"title=%@",title);
    //从网络中下载图片
    NSURL *url = [NSURL URLWithString:@"http://banbao.chazidian.com/uploadfile/2016-01-25/s145368924044608.jpg"];
    //把图片转换成二进制的数据
    NSData *data = [NSData dataWithContentsOfURL:url];
    //把数据转换成图片
    UIImage *image = [UIImage imageWithData:data];
    //回到主线程中设置图片
    //第一种方式
//    [self performSelectorOnMainThread:@selector(settingImage:)
//                           withObject:image
//                        waitUntilDone:NO];
    //第二种方式
//    [self.iconView performSelector:@selector(setImage:)
//                          onThread:[NSThread mainThread]
//                        withObject:image
//                     waitUntilDone:NO];
    //第三种方式
    [self.iconView performSelectorOnMainThread:@selector(setImage:)
                                    withObject:image
                                 waitUntilDone:NO];
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

    //在子线程中调用download方法下载图片
    [self performSelectorInBackground:@selector(download:) withObject:@"下载图片"];
}

- (void)settingImage:(UIImage *)image{
    self.iconView.image = image;
}

@end