Question

i have built a custom viewgroup and m beginning to implement animations tot his viewgroup. the problem i am having is that i need the viewgroup to be able to animate without it’s children being animated by the same animation.

Lets say i am scaling the viewgroup to 2x size, but i still want to keep children at the same size (thus fitting more children into the viewgroup).

Right now i am calling the animation as follows:

    ScaleAnimation expandAnimation =  new ScaleAnimation(1,2,1,2);
    this.startAnimation(expandAnimation);

Thanks in advance! 🙂

Answer 1

You can’t directly do what you’re seeking to do with the old Android animation API. You’ve already noticed one limitation – that scaling the group also includes the children.

The second limitation is that the old Android animation API only affects the visual render of the item you’re animating, and only for the time the animation is active. In other words, it doesn’t actually alter the size or positioning of the item in question in terms of view layout. It only temporarily renders it a different way. So for instance, to animate a button moving from x to y across the screen, you would need to run the animation, then when the animation completes actually reposition the button using the layout APIs.

Probably the way to do what you’re looking for is:

1. Incorporate an extra ViewGroup
   widget in your layout, positioned
   and sized over top the widget
   containing the “real” items.
   Initially, it’s invisible.
2. Make
   it visible, and play the animation.
3. When animation complete, hide the
   extra widget, then resize your real
   ViewGroup widget via LayoutParams
   and add your extra items.
4. You’ll
   probably need to tweak this general
   outline to make the effect look
   smooth. (For instance, resize the real viewgroup in the background before you remove the fake viewgroup from the screen).

Android introduced a newer, more flexible animation API in 3.0 Honeycomb, but unfortunately it’s not available if you’re targeting 2.x devices (i.e., phones). Hopefully this will be easier once the new APIs are mainstream.