UIButton加载网络图片

1、通过NSData加载图片：

[photoBtn setImage:[UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]]] forState:UIControlStateNormal];

2、通过GCD加载：

[photoBtn setImage:[UIImage imageNamed:@"icon_Image_Placeholder"] forState:UIControlStateNormal];  //!< 加这句可以设置button占位图片

UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]]];

      dispatch_async(dispatch_get_main_queue(), ^{

          if(img) {

            [photoBtnsetImage:imgforState:UIControlStateNormal];

           }

       });

 });

3、通过SDWebImage加载,带缓存：

[photoBtn.imageView sd_setImageWithURL:[NSURL URLWithString:imageUrl] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {

       if(image) {

           [photoBtn setImage:image forState:UIControlStateNormal];

        }

}];