iPad有时不使用前凸轮

Question

在我的应用程序中，我必须使用ipad的前凸轮，我必须使用前凸轮拍摄照片。我正在使用[self.imagePickerController takePicture];方法自动拍照 有倒计时，倒数后，应用程序会自动拍照。用户可以拍摄多张照片。当用户拍摄第一张照片时，应用程序使用前凸轮，但当用户拍摄第二张照片时，应用程序正在使用后凸轮，我只想使用前凸轮。请帮忙。 我的代码如下：

- (IBAction)btnTakePic:(id)sender;
{
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {

        //[[UIDevice currentDevice] setOrientation:UIInterfaceOrientationLandscapeRight];

        //Set Notifications so that when user rotates phone, the orientation is reset to landscape.
        [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];

        imagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera;


        imagePickerController.delegate = self;
        imagePickerController.showsCameraControls = NO;

        imagePickerController.cameraDevice= UIImagePickerControllerCameraDeviceFront;


        [imagePickerController setWantsFullScreenLayout:YES];

        [self presentModalViewController:imagePickerController animated:YES];
    }

    [NSTimer scheduledTimerWithTimeInterval:3.0
                                     target:self
                                   selector: @selector(targetMethod)
                                   userInfo:nil
                                    repeats:NO];
}
- (void)targetMethod
{
    [self.imagePickerController takePicture];

}