Sliding Up UITextFields which are hidden by the keyboard in iOS

First, declare the following constants somewhere at the top of the view controller's implementation file. 


CGFloat animatedDistance;

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;


When the textfield will be touched, we will get the rect of the textfield and convert everything to the window coordinates.

Then we calculate the fraction between the top and bottom of the middle section for the text field's midline.

Then we will clamp this fraction so that the top section is all "0.0" and the bottom section is all "1.0".

Then this fraction is converted to scroll according to the keyboards height.

Finally, apply the animation.


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

// get the bound

activeField = textField;

CGRect textFieldRect =

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

CGRect viewRect =

[self.view.window convertRect:self.view.bounds fromView:self.view];

//calculate the fraction between the top and bottom of the middle section

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;

//clamping is done here

if (heightFraction < 0.0) { 
heightFraction = 0.0; 
} 

else if (heightFraction > 1.0) { 
heightFraction = 1.0; 
} 

//converted to the scroll amount 

UIInterfaceOrientation orientation =

[[UIApplication sharedApplication] statusBarOrientation];

if (orientation == UIInterfaceOrientationPortrait ||

orientation == UIInterfaceOrientationPortraitUpsideDown) { 

animatedDistance = floor(PORTRAIT_KEYBOARD_HEIGHT * heightFraction);

}

else

{

animatedDistance = floor(LANDSCAPE_KEYBOARD_HEIGHT * heightFraction);

}

//apply the animation.

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];

}


After that we need to Animate back again. It is done by the following code segment:


- (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];

}

Credits: http://www.cocoawithlove.com/2008/10/sliding-uitextfields-around-to-avoid.html