My app has a UIView called stepView that needs to grow and shrink, always expanding down and to the right, and always shrinking up and to the left. It has a subview, durationLabel, which runs along the entire width of the stepView and has a fixed height.
When the stepView is animated to grow larger, the label grows properly along with it: the text and the label's background slide to the right in sync with the growing stepView. However, when the stepView is animated to grow smaller, it immediately snaps to its new size, leaving a gap between the stepView's shrinking right edge and its right edge until the animation completes.
The label initialization code in stepView.m:
CGRect duration_frame = CGRectMake(0, 0, self.frame.size.width, HEADER_HEIGHT);
self.durationLabel = [[UILabel alloc] initWithFrame:duration_frame];
[self.durationLabel setAutoresizingMask:UIViewAutoresizingFlexibleWidth];
[self addSubview:self.durationLabel];
And the animation code:
[UIView animateWithDuration:ANIM_DURATION
animations:^{
[stepView setFrame:newFrame];
}
];
Using bounds/center instead of frame produces the same effect. I've considered using a transform instead, but the code for calculating "newFrame" is somewhat involved, so I'd rather avoid rewriting it if possible. I've also tried manually changing the label's frame in the same animation block, but that simply makes it disappear entirely (possibly because I was trying to animate both a view's frame and its subview's frame in the same animation block?). I've also confirmed stepView and its subviews aren't undergoing any other animations at the same time, although there are animations happening to unrelated views in separate animation blocks.
I'm at a loss for why the label should animate perfectly when the stepView grows but fail to animate at all when it shrinks. I haven't seen anything in the documentation that indicates there would be a difference. Thank you for any help you can provide.