UIKeyboardWillShowNotification 监听键盘高度变化

UIKeyboardWillShowNotification 通知来获得当键盘改变时，该键盘的高度和位置。

然后调整自己相应的UI元素位置即可，示例代码如下：

-(void)viewDidLoad{

[superviewDidLoad];

[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWillShow:)
name:UIKeyboardWillShowNotification object:nil];

}

-(void)viewDidUnload{

[superviewDidUnload];

[[NSNotificationCenter defaultCenter]removeObserver:self];

}

-(void)keyboardWillShow:(NSNotification*)notification{

NSDictionary*info=[notification userInfo];

CGSize kbSize=[[info objectForKey:UIKeyboardFrameEndUserInfoKey]CGRectValue].size;

NSLog(@"keyboard changed, keyboard width = %f, height = %f",

kbSize.width,kbSize.height);

//在这里调整UI位置

}