多线程之iOS线程间通信

• 什么叫做线程间通信

  • 在1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

• 1个线程传递数据给另1个线程

• 在1个线程中执行完特定任务后，转到另1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;

• 示例 - 图片下载

图片下载.png

代码(PS:里面用到的图片URL取至百度，如果有版权问题，请告知本人，本人会尽快删除)：

//
//  ViewController.m
//  CommunicationBetweenThreads-线程间通信
//
//  Created by wenjim on 17/4/6.
//  Copyright © 2017年 WenJim. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic,strong) UIImageView * imageView;

@property (nonatomic,strong) UIButton * clickBtn;



@end

@implementation ViewController

-(UIImageView *)imageView
{
    if (!_imageView) {
        _imageView = [[UIImageView alloc]initWithFrame:CGRectMake(self.view.bounds.size.width / 2 - 40, self.view.bounds.size.height / 2 - 150, 100, 100)];
        _imageView.backgroundColor = [UIColor redColor];
        _imageView.clipsToBounds = YES;
        _imageView.contentMode = UIViewContentModeScaleAspectFill;
        
    }
    return _imageView;
}

-(UIButton *)clickBtn
{
    if (!_clickBtn) {
        _clickBtn = [UIButton buttonWithType:UIButtonTypeCustom];
        _clickBtn.frame = CGRectMake(self.view.bounds.size.width / 2 - 40, self.view.bounds.size.height / 2 - 10, 80, 20);
        [_clickBtn setTitle:@"下载" forState:UIControlStateNormal];
        [_clickBtn setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
        [_clickBtn addTarget:self action:@selector(setDownloadBtn:) forControlEvents:UIControlEventTouchUpInside];
        
    }
    return _clickBtn;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self setUpAllControls];
}


#pragma mark - UI控件布局
-(void)setUpAllControls
{
    [self.view addSubview:self.imageView];
    
    [self.view addSubview:self.clickBtn];
}


/*
 *    获取当前的时间
 *    // 获得当前的时间
 *   NSDate * startDate = [NSDate date];
 *
 *   // 获取结束时间
 *   NSDate * endDate = [NSDate date];
 *
 *
 */

/*
 *   用C语言获取当前时间
 *    // 获得当前时间 － 绝对时间
 *    CFTimeInterval  start = CFAbsoluteTimeGetCurrent();
 *
 *    // 获得当前时间 － 绝对时间
 *    CFTimeInterval  end = CFAbsoluteTimeGetCurrent();
 *
 *
 */

-(void)setDownloadBtn:(UIButton *)clickBtn
{
    [NSThread detachNewThreadSelector:@selector(downloadImg) toTarget:self withObject:nil];
    
}

-(void)downloadImg
{
    // https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1491485515021&di=b71bf37fbc13415e74dfe073a9fa6154&imgtype=0&src=http%3A%2F%2Ffun.youth.cn%2Fyl24xs%2F201608%2FW020160824572760273145.png
    
    
    // 1. 确定URL
    NSURL * url = [NSURL URLWithString:@"https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1491485515021&di=b71bf37fbc13415e74dfe073a9fa6154&imgtype=0&src=http%3A%2F%2Ffun.youth.cn%2Fyl24xs%2F201608%2FW020160824572760273145.png"];
    
    // 2. 根据URL下载图片 二进制数据 到本地
    NSData * imageData = [NSData dataWithContentsOfURL:url];
    
    // 3. 二进制数据 转换图片格式
    UIImage * image = [UIImage imageWithData:imageData];
    
    NSLog(@"download----%@",[NSThread currentThread]);
    
    
    // 4. 回到主线程刷新显示UI
    /*
     第一参数： 回到主线程要调用哪个方法
     第二参数： 前面的方法需要传递的参数，此处就是image
     第三参数： 是否等待子线程完成
     */
//    [self performSelectorOnMainThread:@selector(showImage:) withObject:image waitUntilDone:YES];
    
    
    // 另外一种线程通信方法
//    [self performSelector:@selector(showImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:YES];
    
    
    // 简单方法
    [self.imageView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:YES];
    
    NSLog(@"-----end------");
    
    
}

#pragma mark -  用Object － C获取当前时间
-(void)downloadImgObjectC
{
    // 1. 确定URL
    NSURL * url = [NSURL URLWithString:@"https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1491485515021&di=b71bf37fbc13415e74dfe073a9fa6154&imgtype=0&src=http%3A%2F%2Ffun.youth.cn%2Fyl24xs%2F201608%2FW020160824572760273145.png"];
    
    
    
    // 2. 根据URL下载图片 二进制数据 到本地
    NSData * imageData = [NSData dataWithContentsOfURL:url];
    
    // 获得当前的时间
    NSDate * startDate = [NSDate date];
    
    // 3. 二进制数据 转换图片格式
    UIImage * image = [UIImage imageWithData:imageData];
    
    // 获取结束时间
    NSDate * endDate = [NSDate date];
    
    NSLog(@"%f",[endDate timeIntervalSinceDate:startDate]);
    
    // 4. 显示UI
    
    self.imageView.image = image;
}

#pragma mark -  用C语言获取时间
-(void)downloadC
{
    // 1. 确定URL
    NSURL * url = [NSURL URLWithString:@"https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1491485515021&di=b71bf37fbc13415e74dfe073a9fa6154&imgtype=0&src=http%3A%2F%2Ffun.youth.cn%2Fyl24xs%2F201608%2FW020160824572760273145.png"];
    
    
    
    // 2. 根据URL下载图片 二进制数据 到本地
    NSData * imageData = [NSData dataWithContentsOfURL:url];
    
    // 用C语言获取当前时间
    // 获得当前时间 － 绝对时间
    CFTimeInterval  start = CFAbsoluteTimeGetCurrent();
    
    
    
    // 3. 二进制数据 转换图片格式
    UIImage * image = [UIImage imageWithData:imageData];
    
    // 获得当前时间 － 绝对时间
    CFTimeInterval  end = CFAbsoluteTimeGetCurrent();
    
    NSLog(@"end - start = %f",end - start);
    
    // 4. 显示UI
    
    self.imageView.image = image;
}


#pragma mark -  刷新图片
-(void)showImage:(UIImage *)image
{
    self.imageView.image = image;
    NSLog(@"UI ----- %@",[NSThread currentThread]);
}

@end