Dynamically animate a layout

Question

I have to implement a (child) layout translate animation programmatically because the distance to translate is determined at runtime. I have set the following translate animation

    TranslateAnimation tanim = new TranslateAnimation(
        TranslateAnimation.ABSOLUTE, 0.0f,
        TranslateAnimation.ABSOLUTE, 0.0f,
        TranslateAnimation.ABSOLUTE, 0.0f,
        TranslateAnimation.ABSOLUTE, 100);

to slide down the layout, for example.

Problem 1: This layout will snap back to its original position after the animation finishes. Is there anything I should set to maintain its position? I suspect this is caused by the layout being moved out of the parent layout (parent layout has parameter layout_width="wrap_content"). If this is the case how can I adjust the parent layout to accomodate the child layout change?

Problem 2: Do I have to provide a custom interpolator class to achieve a decelerating effect? If yes, do you know where can I find an example? In xml I can do this

android:interpolator="@android:anim/accelerate_interpolator"

Is there an equivalent Android code to achieve the accelerate/decelerate effect programmatically?

Answer 1

to keep the position after the animation you need to use the fillAfter attribute. And yes there are Accelerate and Decelerate interpolater classes within the public APIs

TranslateAnimation tanim = new TranslateAnimation(
        TranslateAnimation.ABSOLUTE, 0.0f,
        TranslateAnimation.ABSOLUTE, 0.0f,
        TranslateAnimation.ABSOLUTE, 0.0f,
        TranslateAnimation.ABSOLUTE, 100);
tanim.setFillAfter(true);
tanim.setInterpolater(new DecelerateInterpolator());
//tanim.setInterpolater(new AccelerateInterpolator());

See the Animation docs for info about fillAfter and the Interpolator docs for a list of the built in Interpolator objects within the system.