ios：从系统相册选取视频并获得视频的缩略图

在UIImagePickerControllerDelegate的函数- (void)imagePickerController:(UIImagePickerController *)picker   didFinishPickingMediaWithInfo:(NSDictionary *)info 中实现：

- (void)imagePickerController:(UIImagePickerController *)picker   didFinishPickingMediaWithInfo:(NSDictionary *)info 

{   

    [pickerdismissModalViewControllerAnimated:YES];

   NSString*mediaType = [infoobjectForKey:UIImagePickerControllerMediaType];

    if([mediaType isEqualToString:@"public.movie"])

    {

       NSURL*videoURL = [infoobjectForKey:UIImagePickerControllerMediaURL];

       NSLog(@"found a video");

        //获取视频的thumbnail     

       MPMoviePlayerController*player = [[[MPMoviePlayerControlleralloc]initWithContentURL:videoURL] autorelease];

       UIImage  *thumbnail = [playerthumbnailImageAtTime:1.0timeOption:MPMovieTimeOptionNearestKeyFrame];

player = nil;

        }

}