23、[ iOS ] 键盘的监听事件 - 通知

首先在 viewDidLoad 中添加

//增加监听，当键盘出现或改变时收到消息
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
//增加监听，当键盘退出时收到消息
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];

然后实现两个通知中的方法

/**
 * 功能：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 KBHeight              = keyboardRect.size.height;

    // ------键盘出现或改变时的操作代码
}

/**
 * 功能：当键盘退出时调用
 */
- (void)keyboardWillHide:(NSNotification *)aNotification {
   // ------键盘退出时的操作代码
}