Textfield hide when keyboard open

//write this code in viewdidload method

[[NSNotificationCenter defaultCenter] addObserver:self

                                             selector:@selector(keyboardWillShow:)

                                                 name:UIKeyboardWillShowNotification

                                               object:self.view.window];

    // register for keyboard notifications

    [[NSNotificationCenter defaultCenter] addObserver:self

                                             selector:@selector(keyboardWillHide:)

                                                 name:UIKeyboardWillHideNotification

                                               object:self.view.window];

    keyboardIsShown = NO;

- (void)keyboardWillHide:(NSNotification *)n

{

    NSDictionary* userInfo = [n userInfo];

    

    // get the size of the keyboard

    CGSize keyboardSize = [[userInfo objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;

    

    

    // resize the scrollview

    CGRect viewFrame = scrView.frame;

    // I'm also subtracting a constant kTabBarHeight because my UIScrollView was offset by the UITabBar so really only the portion of the keyboard that is leftover pass the UITabBar is obscuring my UIScrollView.

    viewFrame.size.height += (keyboardSize.height - 100);

    

    [UIView beginAnimations:nil context:NULL];

    [UIView setAnimationBeginsFromCurrentState:YES];

    [scrView setFrame:viewFrame];

    [UIView commitAnimations];

    

    keyboardIsShown = NO;

}

- (void)keyboardWillShow:(NSNotification *)n

{

    // This is an ivar I'm using to ensure that we do not do the frame size adjustment on the `UIScrollView` if the keyboard is already shown.  This can happen if the user, after fixing editing a `UITextField`, scrolls the resized `UIScrollView` to another `UITextField` and attempts to edit the next `UITextField`.  If we were to resize the `UIScrollView` again, it would be disastrous.  NOTE: The keyboard notification will fire even when the keyboard is already shown.

    if (keyboardIsShown) {

        return;

    }

    

    NSDictionary* userInfo = [n userInfo];

    

    // get the size of the keyboard

    CGSize keyboardSize = [[userInfo objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;

    

    // resize the noteView

    CGRect viewFrame = scrView.frame;

    // I'm also subtracting a constant kTabBarHeight because my UIScrollView was offset by the UITabBar so really only the portion of the keyboard that is leftover pass the UITabBar is obscuring my UIScrollView.

    viewFrame.size.height -= (keyboardSize.height - 100);

    

    [UIView beginAnimations:nil context:NULL];

    [UIView setAnimationBeginsFromCurrentState:YES];

    [scrView setFrame:viewFrame];

    [UIView commitAnimations];

    [scrView scrollRectToVisible:activeField.frame animated:YES];

    keyboardIsShown = YES;

}

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField{

    activeField = textField;

    return YES;

}