收到一个变态的需求：调起系统照相机，默认闪关灯关闭
无效做法：
UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
imagePicker.cameraCaptureMode = UIImagePickerControllerCameraCaptureModePhoto;
imagePicker.cameraFlashMode = UIImagePickerControllerCameraFlashModeOff;//没有作用
[self presentViewController:imagePicker animated:YES completion:nil];
有效做法：UIImagePickerController.delegate的代理方法
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
if (imagePicker.sourceType == UIImagePickerControllerSourceTypeCamera) {
imagePicker.cameraCaptureMode = UIImagePickerControllerCameraCaptureModePhoto;
imagePicker.cameraFlashMode = UIImagePickerControllerCameraFlashModeOff;
}
}
