从系统相册选取视频并获得视频的缩略图（取消自动播放）

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

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

{   

    [picker dismissModalViewControllerAnimated: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];

      // 获取到的视频会自动播放，如果要取消播放那就加上这句话 player.shouldAutoplay = NO;

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

player = nil;

        }

}