Correctly Using CGAffineTransformMakeScale

Question

I have a UIButton laid out using storyboard. The button just contains an image. When the button is clicked, I want to animate the size of the button - decrease in size and then bring it back to the original size again.

I used the following code -

[UIView animateWithDuration:2.0 animations:^{
    _favButton.transform = CGAffineTransformMakeScale(0.5, 0.5);
}completion:^(BOOL finished) {
    [UIView animateWithDuration:2.0 animations:^{
          _favButton.transform = CGAffineTransformMakeScale(1, 1);
    }];
}];

This code moves my button on the screen which I do not want. I want the center of the button to be fixed and the size be animated.

I have not used any Top Constraint in the storyboard for the button. How can I rectify this behaviour?

Answer 1

If you have auto layout turned on, you would need to turn it off.

But it doesn't seem to your problem here as per your description.

I would do the following to re-adjust to the center as it scales:

CGPoint cP = _favButton.center;

[UIView animateWithDuration:2.0 animations:^
{
    _favButton.transform = CGAffineTransformMakeScale(0.5, 0.5);
    _favButton.layer.position = cp;
}
completion:^(BOOL finished) 
{
    [UIView animateWithDuration:2.0 animations:^
    {
        _favButton.transform = CGAffineTransformMakeScale(1, 1);
        _favButton.layer.position = cp;
    }];
}];

Hope this helps.