iOS 获取网络视频第一帧

现在的后台越来越懒了，本来列表里面的图片属性应该返回一个图片的URL地址。
但是奇葩的后台会返回两种，一种是图片链接，一种是视频链接、如果是视频的
话就需求自己取视频的第一帧，而且还没有字段判断该链接是图片链接还是视频链接，这也难道不到咱。实现方法如下。

#import "VideoHelper.h"
#import <AVFoundation/AVAsset.h>
#import <AVFoundation/AVAssetImageGenerator.h>
#import <AVFoundation/AVTime.h>
#import <SDWebImage/SDImageCache.h>


@implementation VideoHelper

+(void)getVideoPreViewImageURL:(NSString *)videoURL forImageView:(BaseImageView *)imageView placeHolderImage:(UIImage *)placeHolder
{

    [[SDImageCache sharedImageCache] queryCacheOperationForKey:videoURL done:^(UIImage * _Nullable image, NSData * _Nullable data, SDImageCacheType cacheType) {
         //是否有缓存图片
        if(image){
            imageView.image = image;
        }else{
            //获取视频第一帧
            [self getVideoFirstViewImage:videoURL forImageView:imageView placeHolderImage:placeHolder];
        }
    }];
}

// 获取视频第一帧
+ (void)getVideoFirstViewImage:(NSString *)videoURL forImageView:(BaseImageView *)imageView placeHolderImage:(UIImage *)placeHolder {
   
    NSString *url = [NSString stringWithFormat:@"%@?flag=2",videoURL];
    __block UIImage *videoImage;
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:[NSURL URLWithString:url] options:nil];
        NSParameterAssert(asset);
        AVAssetImageGenerator *assetImageGenerator =[[AVAssetImageGenerator alloc] initWithAsset:asset];
        assetImageGenerator.appliesPreferredTrackTransform = YES;
        assetImageGenerator.apertureMode =AVAssetImageGeneratorApertureModeEncodedPixels;
        CGImageRef thumbnailImageRef = NULL;
        NSError *thumbnailImageGenerationError = nil;
        thumbnailImageRef = [assetImageGenerator copyCGImageAtTime:CMTimeMake(0, 60)actualTime:NULL error:&thumbnailImageGenerationError];
        if(!thumbnailImageRef)
        NSLog(@"thumbnailImageGenerationError %@",thumbnailImageGenerationError);
        videoImage = thumbnailImageRef ? [[UIImage alloc]initWithCGImage:thumbnailImageRef]: nil;
        
        dispatch_async(dispatch_get_main_queue(), ^{
            //主线程更新UI
            if(videoImage){
                imageView.image = videoImage;
                //缓存图片
                [[SDImageCache sharedImageCache] storeImage:videoImage forKey:videoURL toDisk:NO completion:^{
                    
                }];
                
            }else{
                //如果不是视频就设置图片
                [imageView setImageUrl:videoURL placeholderImage:placeHolder];
            }
        });
          
    });

}

@end