iPhone获取键盘高度，通知方式隐藏和显示键盘
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWasShown:) name:UIKeyboardDidShowNotification object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWasHidden:) name:UIKeyboardDidHideNotification object:nil];


- (void) keyboardWasShown:(NSNotification *) notif{
NSDictionary *info = [notif userInfo];
NSValue *value = [info objectForKey:UIKeyboardFrameBeginUserInfoKey];
CGSize keyboardSize = [value CGRectValue].size;

NSLog(@"keyBoard:%f", keyboardSize.height); //216
keyboardWasShown = YES;
}

- (void) keyboardWasHidden:(NSNotification *) notif{
NSDictionary *info = [notif userInfo];

NSValue *value = [info objectForKey:UIKeyboardFrameBeginUserInfoKey];
CGSize keyboardSize = [value CGRectValue].size;
NSLog(@"keyboardWasHidden keyBoard:%f", keyboardSize.height);
keyboardWasShown = NO;

}