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; 
    
}