View resizes to full screen after app becomes active

My situation:

I have a text input field at the bottom of my view (the outermost view does not scroll). When someone focuses the input, I shrink the view to accomodate the keyboard (specifically, I subtract the height of the keyboard and animate the view to a new height).

My problem:

Whenever something takes focus away from my ViewController and returns it soon after (e.g. a push notification or someone hitting the home button and coming back to the app later), the view seems to automatically resize so that the text input is back at the bottom of the screen, but the ke开发者_StackOverflowyboard remains showing.

What I want:

I want the view to maintain the size it had before the app regained focus. The keyboard should remain showing and the text input show display above it, not move back down to the bottom of the screen behind the keyboard.

Does anyone know what I might be doing wrong or what I need to do to get this behavior?

---

try this code....

    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;



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

     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];
    }



 - (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];
}

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

    [textField resignFirstResponder];
    return YES;
}