CODEWITHSUNDEEP
iphoneiosanimationuiview
Mike
Mike

Reputation: 2409

Animate UIView grow/shrink

I have a UILabel I want to animate growing and shrinking. While the size changes I need the bottom left corner to remain static so that it always appears directly above a bottom toolbar. I am using the following code to make the label grow: 

[UIView animateWithDuration:kAnimationDuration delay:0.0 options:UIViewAnimationCurveEaseInOut 
                 animations:^{  
    CGFloat lblHeight = 42.0f;
    [label setFrame:CGRectMake(0.0, 
                CGRectGetMaxY(self.view.bounds) - kBottomBarHeight - lblHeight, 
                CGRectGetMaxX(self.view.bounds), 
                lblHeight)];                
} completion:^(BOOL finished) { }];

and to make it shrink I use the same logic except that lblHeight is set to 17.0f

The view correctly grows but when I try to shrink it the frame change animation is not animated. It blips into the new size and then animates into the new origin/location. I need the frame change to be animated. Can anyone see what I'm doing wrong?

Upvotes: 5

Views: 6183

Answers (2)

Mike
Mike

Reputation: 2409

After some tinkering I've managed to get the desired behavior by doing the following.

In the expand method, I use the UIView animation to alter the frame. In the shrink method, I use the UIView animation to alter the bounds and center.

I'm a little baffled as to why this works but trying to shrink with the frame does not. If anyone can share some insight into this that would be great.

Upvotes: 2

Kaan Dedeoglu
Kaan Dedeoglu

Reputation: 14841

You should not really use frames to animate, rather you should use the transform property of your label.

However, since you want one corner to remain static, I think its best you use Core Animation. CALayer has a property called anchorPoint that determines which point a layer will rotate with respect to, and I'm pretty sure it is also valid for grow/shrink effects.

Upvotes: 0

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