我有一个简单的viewController，我想监听UIKeyboardWillHideNotification。因此我有以下代码:-(void)viewWillAppear:(BOOL)animated{[superviewWillAppear:animated];[[NSNotificationCenterdefaultCenter]addObserver:selfselector:@selector(keyboardWillBeHidden)name:UIKeyboardWillHideNotificationobject:nil];}-(void)keyboardWillBeH