线程间通信

线程间通信就是子线程和主线程之间的通信

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *imageView;

@end

@implementation ViewController

#pragma mark ----------------------
#pragma Events

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

  //开辟新线程去执行方法
    [NSThread detachNewThreadSelector:@selector(download) toTarget:self withObject:nil];
}

#pragma mark ----------------------
#pragma Methods

//开子线程下载图片,回到主线程刷新UI
-(void)download
{
    //1.确定URL
    NSURL *url = [NSURL URLWithString:@"http://img4.duitang.com/uploads/blog/201310/18/20131018213446_smUw4.thumb.700_0.jpeg"];
    
    //2.根据url下载图片二进制数据到本地
    NSData *imageData = [NSData dataWithContentsOfURL:url];
    
    //3.转换图片格式
    UIImage *image = [UIImage imageWithData:imageData];
    
    NSLog(@"download----%@",[NSThread currentThread]);
    
    //4.回到主线程显示UI
    /*
     第一个参数:回到主线程要调用哪个方法
     第二个参数:前面方法需要传递的参数 此处就是image
     第三个参数:是否等待
     */
    //[self performSelectorOnMainThread:@selector(showImage:) withObject:image waitUntilDone:NO];
    
//    [self performSelector:@selector(showImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:YES];
    
    [self.imageView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:YES];
    
//    self.imageView.image = image;
    NSLog(@"---end---");
}

//计算代码段执行时间的第一种方法
-(void)download1
{
    //0.000018
    //0.166099
    
    //1.确定URL
    NSURL *url = [NSURL URLWithString:@"http://img4.duitang.com/uploads/blog/201310/18/20131018213446_smUw4.thumb.700_0.jpeg"];

    NSDate *start = [NSDate date];  //获得当前的时间
    
    //2.根据url下载图片二进制数据到本地
    NSData *imageData = [NSData dataWithContentsOfURL:url];
    
    NSDate *end = [NSDate date];  //获得当前的时间
    NSLog(@"%f",[end timeIntervalSinceDate:start]);
    
    //3.转换图片格式
    UIImage *image = [UIImage imageWithData:imageData];
    
    //4.显示UI
    self.imageView.image = image;
}

//计算代码段执行时间的第二种方法
-(void)download2
{
    //1.确定URL
    NSURL *url = [NSURL URLWithString:@"http://img4.duitang.com/uploads/blog/201310/18/20131018213446_smUw4.thumb.700_0.jpeg"];
    
    CFTimeInterval start = CFAbsoluteTimeGetCurrent();
    
    //2.根据url下载图片二进制数据到本地
    NSData *imageData = [NSData dataWithContentsOfURL:url];
    
    CFTimeInterval end = CFAbsoluteTimeGetCurrent();
    NSLog(@"end-start = %f---%f---%f",end - start,end,start);
    
    //3.转换图片格式
    UIImage *image = [UIImage imageWithData:imageData];
    
    //4.显示UI
    self.imageView.image = image;
}

//更新UI操作
-(void)showImage:(UIImage *)image
{
    self.imageView.image = image;
    NSLog(@"UI----%@",[NSThread currentThread]);
}

@end