监听键盘高度

在遇到有输入的情况下。由于现在键盘的高度是动态变化的。中文输入与英文输入时高度不同。所以输入框的位置也要做出相应的变化

添加监听事件：

//增加监听，当键盘出现或改变时收出消息    [[NSNotificationCenter defaultCenter] addObserver:self                                             selector:@selector(keyboardWillShow:)                                                 name:UIKeyboardWillShowNotification//这个是带系统动画的 //UIKeyboardDidShowNotification 键盘出来后再出现，不带动画                                              object:nil];        //增加监听，当键退出时收出消息    [[NSNotificationCenter defaultCenter] addObserver:self                                             selector:@selector(keyboardWillHide:)                                                 name:UIKeyboardWillHideNotification                                               object:nil];        

//当键盘出现或改变时调用- (void)keyboardWillShow:(NSNotification *)aNotification{    //获取键盘的高度    NSDictionary *userInfo = [aNotification userInfo];    NSValue *aValue = [userInfo objectForKey:UIKeyboardFrameEndUserInfoKey];    CGRect keyboardRect = [aValue CGRectValue];    int height = keyboardRect.size.height;}
//当键退出时调用- (void)keyboardWillHide:(NSNotification *)aNotification{    }