Adjust offset of view when keyboard hides a textfield

adjust_view_frame

- (void)viewWillAppear:(BOOL)animated
{
    // register for keyboard notifications
    [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWillShow)
                                             name:UIKeyboardWillShowNotification
                                           object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWillHide)
                                             name:UIKeyboardWillHideNotification
                                           object:nil];
}

- (void)viewWillDisappear:(BOOL)animated
{
    // unregister for keyboard notifications while not visible.
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                             name:UIKeyboardWillShowNotification
                                           object:nil];

    [[NSNotificationCenter defaultCenter] removeObserver:self
                                             name:UIKeyboardWillHideNotification
                                           object:nil];
}

#pragma mark - UITextField Delegates

-(void)textFieldDidBeginEditing:(UITextField *)textField
{
    self.activeTextField = textField;
}


#pragma mark - Keyboard Notification Methods

-(void)keyboardWillShow:(NSNotification*) notification
{
    
    /*
     This will check if the currently active field will be hidden 
     by the keyboard when it appears. If it will be, view's frame
     will be adjusted upwards so that the active field will be visible.
    */
    
    NSDictionary *info = [notification userInfo];
    CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
    
    CGFloat keyboardHeight = kbSize.height;
    
    NSLog(@"%f", kbSize.height);
    
    CGRect selfViewFrame = self.view.frame;
    selfViewFrame.size.height -= keyboardHeight;
    
    CGPoint activeFieldOrigin = self.activeTextField.frame.origin;
    activeFieldOrigin.y += self.activeTextField.frame.size.height + 10;
    
    if(!CGRectContainsPoint(selfViewFrame, activeFieldOrigin)){
        [UIView beginAnimations:nil context:NULL];
        [UIView setAnimationDuration:0.3];
        
        CGRect selfViewRect = self.view.frame;
        selfViewRect.origin.y -= keyboardHeight - (selfViewRect.size.height - activeFieldOrigin.y);
        
        self.view.frame = selfViewRect;
        
        [UIView commitAnimations];
    }
    
}

-(void)keyboardWillHide:(NSNotification*)notification
{
    
    //Returns the main view's frame back into it's original position.
    
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3];
    
    CGRect selfViewRect = self.view.frame;
    selfViewRect.origin.x = 0;
    selfViewRect.origin.y = 0;
    
    self.view.frame = selfViewRect;
    
    [UIView commitAnimations];
}