iOS 8.1 UIImagePickerController处于视频模式-控件无响应

我正在使用此方法打开摄像头进行视频录制：

if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
    UIImagePickerController *videoRecorder = [[UIImagePickerController alloc]init];
    videoRecorder.delegate = self;
    videoRecorder.sourceType = UIImagePickerControllerSourceTypeCamera;
    videoRecorder.mediaTypes = [NSArray arrayWithObject:(NSString*)kUTTypeMovie];
    videoRecorder.cameraCaptureMode = UIImagePickerControllerCameraCaptureModeVideo;
    videoRecorder.videoQuality = UIImagePickerControllerQualityTypeLow;
    videoRecorder.showsCameraControls = YES;
    videoRecorder.videoMaximumDuration = 20;

    self.imagePicker = videoRecorder;
    [self presentViewController:self.imagePicker animated:YES completion:^{
        //
    }];
}

摄像头打开后，我可以开始录制视频，但在我停止录制后，重拍、播放和使用视频按钮没有响应。原因可能是什么？

发现了问题。 忘记在代理中关闭图像选择器：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    [picker dismissViewControllerAnimated:YES completion:NULL];
}