I have a very simple application. It contains a red view and a green label inside it. There is also a button that runs animation. I animate the red view by changing its width constraint constant's value.
[self.view layoutIfNeeded];
[UIView animateWithDuration:0.4 animations:^{
self.widthConstraint.constant = width;
[self.view layoutIfNeeded];
}];
The red view animates as expected, but the green label inside changes its width instantly. I played with different animation flags, tried several tips from SO but did not bring it work.
Please find the sources here.
TIA
It seems like I've found the root of the problem. Constraints are not a trouble, UILabel is.
If you replace UILabel in my project with simple UIView it will animate smoothly as expected. It's a question of UILabel content animation. You can reach correct animation behaviour set label.contentMode = UIViewContentModeCenter but it looks ugly.
The best way to solve this problem - not try to change size of UILabel during animation. Try to invent some other behaviour. In my case I change UILabel's alpha to 0 and x position to greater then container view's width.
Please find more details about UILabel animating here.
I have took a look at your project. I have not that much experience with setting constraints from editor but I would highly recommend you in case of troubles try to do it in code. Personally I would animate constraint on width of this red view and set constraints on the label's margins using visual format it will be something like: @"H:|[label]|" and add this this constraint to red view. That should solve the problem.
