通过异步下载图片,主队列刷新UI演示线程间的通讯使用
注意点:
1.耗时操作在子线程执行
2.刷新UI在主线程执行
示例代码
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController{
// 图片框
UIImageView *_imageView;
}
- (void)viewDidLoad {
[super viewDidLoad];
// 图片框初始化
_imageView = [[UIImageView alloc] initWithFrame:[UIScreen mainScreen].bounds];
_imageView.contentMode = UIViewContentModeScaleAspectFit;
[self.view addSubview:_imageView];
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
// 下载图片异步执行
dispatch_async(dispatch_get_global_queue(0, 0), ^{
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://m.818today.com/imgsy/image/2016/0113/6358830376853382456131864.jpg"]];
UIImage *downImage = [UIImage imageWithData:data];
// 刷新UI(通过主队列任务在主线程执行的特性,实现GCD子线程回归主线程执行任务)
dispatch_async(dispatch_get_main_queue(), ^{
_imageView.image = downImage;
});
});
}
@end
