我正在尝试获取SLComposeViewController的UITextView，如何获取？我尝试了以下但它不起作用:[viewControllerpresentViewController:facebookControlleranimated:YEScompletion:^{for(UIView*viewLayer1infacebookController.view.subviews){for(UIView*viewLayer2inviewLayer1.subviews){if([viewLayer2isKindOfClass:[UIViewclass]]){for(UIView*