Animate ScrollView on editing UITextField

//Declare in implementation file

static const CGFloat KEYBOARD_ANIMATION_DURATION = 0.3;

static const CGFloat MINIMUM_SCROLL_FRACTION = 0.2;

static const CGFloat MAXIMUM_SCROLL_FRACTION = 0.8;

static const CGFloat PORTRAIT_KEYBOARD_HEIGHT = 216;

//static const CGFloat LANDSCAPE_KEYBOARD_HEIGHT = 162;

#pragma - UITextField Delegates

- (void)textFieldDidBeginEditing:(UITextField *)textField {

    

    //Perform Animation during Keyboard show and Hide

    CGRect textFieldRect = [self.view.window convertRect:textField.bounds fromView:textField];

    CGRect viewRect = [self.view.window convertRect:self.view.bounds fromView:self.view];

    

    CGFloat midline = textFieldRect.origin.y + 0.5 * textFieldRect.size.height;

    CGFloat numerator = midline - viewRect.origin.y - MINIMUM_SCROLL_FRACTION * viewRect.size.height;

    

    CGFloat denominator = (MAXIMUM_SCROLL_FRACTION - MINIMUM_SCROLL_FRACTION) * viewRect.size.height;

    CGFloat heightFraction = numerator / denominator;

    

    if (heightFraction < 0.0) {

        heightFraction = 0.0;

    }

    else if (heightFraction > 1.0) {

        heightFraction = 1.0;

    }

    

    animatedDistance = floor(PORTRAIT_KEYBOARD_HEIGHT * heightFraction);

    

    CGRect viewFrame = self.view.frame;

    viewFrame.origin.y -= animatedDistance;

    

    [UIView beginAnimations:nil context:NULL];

    [UIView setAnimationBeginsFromCurrentState:YES];

    [UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];

    

    [self.view setFrame:viewFrame];

    

    [UIView commitAnimations];

}

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

    

    return YES;

}

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

    

    [textField resignFirstResponder];

    return YES;

}

- (void)textFieldDidEndEditing:(UITextField *)textField {

    

    CGRect viewFrame = self.view.frame;

    viewFrame.origin.y += animatedDistance;

    

    [UIView beginAnimations:nil context:NULL];

    [UIView setAnimationBeginsFromCurrentState:YES];

    [UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];

    

    [self.view setFrame:viewFrame];

    

    [UIView commitAnimations];

}