Animate intrinsicContentSize changes

Question

I have a UIView subclass that draws a circle whose radius changes (with nice bouncy animations). The view is deciding the size of the circle.

I want this UIView subclass

Answer 1

Width / height constraint doesn't help? Keep reference of this constraint and ...

[NSLayoutConstraint constraintWithItem:view
                             attribute:NSLayoutAttributeWidth
                             relatedBy:NSLayoutRelationEqual
                                toItem:nil
                             attribute:NSLayoutAttributeNotAnAttribute
                            multiplier:1
                              constant:myViewInitialWidth];

... when you do want to animate myView resize, do this ...

self.viewWidthConstraint.constant = 100; // new width
[UIView animateWithDuration:0.3 animations:^{ [view layoutIfNeeded]; }];

... do the same thing for the height.

Depends on your other constraints, maybe you will be forced to raise priority of these two constraints.

Or you can subclass UIView, add - (void)invalidateIntrinsicContentSize:(BOOL)animated and fake it by yourself. Get new size from - (CGSize)intrinsicContentSize and animate it by animating width / height constraints. Or add property to enable / disable animations and override invalidateIntrinsicContentSize and do it inside this method. Many ways ...