線程間的通信（3種方式）

三種方法都是通過touchesBegin監聽屏幕的觸摸實現

一、performSelector方式

#import "ViewController.h"
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@end
@implementation ViewController
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    //放入子線程
    [self performSelectorInBackground:@selector(download3) withObject:nil];
}

//下載放入子線程，顯示圖片應該放在主線程！！！否則會導致刷新問題
- (void)download3
{
    //圖片的網絡路徑
    NSURL *url = [NSURL URLWithString:@"http://ww2.sinaimg.cn/mw690/63e6fd01jw1f3f3rf75goj20qo0zkagy.jpg"];
    //下載圖片數據
    NSData *data = [NSData dataWithContentsOfURL:url];
    
    //生成圖片
    UIImage *image = [UIImage imageWithData:data];
    //回到主線程顯示圖片方法一：
//    [self performSelectorOnMainThread:@selector(showImage:) withObject:image waitUntilDone:YES];
    //回到主線程顯示圖片方法二：
    //waitUntilDone:表示是否等待主線程做完事情后往下走，YES表示做完后執行下面事，NO表示跟下面事一起執行
    [self.imageView performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:YES];
    //回到主線程顯示圖片方法三：
    [self.imageView performSelector:@selector(setImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:YES];
}
//主線程顯示圖片
- (void)showImage:(UIImage *)image
{
    self.imageView.image = image;
}

 

二、GCD方式

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        //圖片的網絡途徑
        NSURL *url = [NSURL URLWithString:@"http://ww2.sinaimg.cn/mw1024/75614297jw1f34e5llyz4j20qo0zj0zl.jpg"];
        //加載圖片
        NSData *data = [NSData dataWithContentsOfURL:url];
        //生成圖片
        UIImage *image = [UIImage imageWithData:data];\
        //回到主線程
        dispatch_async(dispatch_get_main_queue(), ^{
            self.imageView.image = image;
        });
    });
    
}

 

三、operation方式(此種方式更具有面向對象特性！)

 

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    //直接開始子線程執行任務
    [[[NSOperationQueue alloc] init] addOperationWithBlock:^{
        NSURL *url = [NSURL URLWithString:@"http://ww4.sinaimg.cn/mw690/63e6fd01jw1ezxz499hy5j21gt0z94qq.jpg"];
        NSData *data = [NSData dataWithContentsOfURL:url];
        UIImage *image = [UIImage imageWithData:data];
        //回到主線程
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            //顯示圖片
            self.imageView.image = image;
        }];
    }];
}

 

以上三種方式都需要在main storyboard中拖一個imageView，然后設置自動布！！