iOS UITextField Delegate methods to animate view frames up and down on keyboard appearance/disappearance

UITextFieldDelegates

#pragma mark - Text Editing functions
    
    - (BOOL)textFieldShouldReturn:(UITextField *)textField
    {
    	[textField resignFirstResponder];
    	  	
    	return YES;
    }
    
    
    - (void)textFieldDidEndEditing:(UITextField *)textField
    {
    	CGRect viewFrame = self.frame;
    	viewFrame.origin.y += animatedDistance;
    	
    	[UIView beginAnimations:nil context:NULL];
    	[UIView setAnimationBeginsFromCurrentState:YES];
    	[UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];
    	
    	self.frame = viewFrame;
    	
    	[UIView commitAnimations];
    }
    
    
    - (void) textFieldDidBeginEditing:(UITextField*) textField {
    	CGRect	textFieldRect	= [self.window convertRect:textField.bounds fromView:textField];
    	CGRect	viewRect		= [self.window convertRect:self.bounds fromView:self];
    	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.frame;
    	viewFrame.origin.y -= animatedDistance;
    	
    	[UIView beginAnimations:nil context:NULL];
    	[UIView setAnimationBeginsFromCurrentState:YES];
    	[UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];
    	
    	self.frame = viewFrame;
    	
    	[UIView commitAnimations];
    }