到目前为止，我有以下内容letassetUrl=NSURL.URLWithString(self.targetVideoString)letasset:AVAsset=AVAsset.assetWithURL(assetUrl)asAVAssetletimageGenerator=AVAssetImageGenerator(asset:asset);lettime:CMTime=CMTimeMakeWithSeconds(1.0,1)letactualTime:CMTimeletmyImage:CGImage=imageGenerator.copyCGImageAtTime(reque