UIKeyboard avoidance and Auto Layout

Question

Given the focus on Auto Layout in iOS 6, and the recommendation by Apple engineers (see WWDC 2012 videos) that we no longer manipulate a views\' frame directly, how wou

Answer 1

I created a view like this that would watch the keyboard and change its own constraints when the keyboard comes on/off the screen.

@interface YMKeyboardLayoutHelperView ()
@property (nonatomic) CGFloat desiredHeight;
@property (nonatomic) CGFloat duration;
@end

@implementation YMKeyboardLayoutHelperView

- (id)init
{
    self = [super init];
    if (self) {
        self.translatesAutoresizingMaskIntoConstraints = NO;

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

- (void)keyboardWillShow:(NSNotification *)notification
{
    // Save the height of keyboard and animation duration
    NSDictionary *userInfo = [notification userInfo];
    CGRect keyboardRect = [userInfo[@"UIKeyboardBoundsUserInfoKey"] CGRectValue];
    self.desiredHeight = CGRectGetHeight(keyboardRect);
    self.duration = [userInfo[@"UIKeyboardAnimationDurationUserInfoKey"] floatValue];

    [self setNeedsUpdateConstraints];
}

- (void)keyboardWillHide:(NSNotification *)notification
{
    // Reset the desired height (keep the duration)
    self.desiredHeight = 0.0f;

    [self setNeedsUpdateConstraints];
}

- (void)updateConstraints
{
    [super updateConstraints];

    // Remove old constraints
    if ([self.constraints count]) {
        [self removeConstraints:self.constraints];
    }

    // Add new constraint with desired height
    NSString *constraintFormat = [NSString stringWithFormat:@"V:[self(%f)]", self.desiredHeight];
    [self addVisualConstraints:constraintFormat views:@{@"self": self}];

    // Animate transition
    [UIView animateWithDuration:self.duration animations:^{
        [self.superview layoutIfNeeded];
    }];

}

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

@end