iOS监听系统键盘的出现和消失

//注册键盘出现的通知

    [[NSNotificationCenter defaultCenter] addObserver:self

                                             selector:@selector(keyboardWasShown:)

                                                 name:UIKeyboardWillShowNotification object:nil];

    //注册键盘消失的通知

    [[NSNotificationCenter defaultCenter] addObserver:self

                                             selector:@selector(keyboardWillBeHidden:)

                                                 name:UIKeyboardWillHideNotification object:nil];

- (void)keyboardWasShown:(NSNotification*)aNotification

{

    //键盘高度

    CGRect keyBoardFrame = [[[aNotification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

}


-(void)keyboardWillBeHidden:(NSNotification*)aNotification

{


}