CollapseAnimation

/**
 * This animation supports API >= 10
 */
public class CollapseAnimation extends Animation
{
// -- Construction

    /**
     *
     * @param view The view to be animated
     * @param startingHeight
     * @param endingHeight
     * @param down True = expanding, false = collapsing
     */
    public CollapseAnimation(View view, int startingHeight, int endingHeight, boolean down, long duration)
    {
        this.mView = view;
        this.mStartingHeight = startingHeight;
        this.mEndingHeight = endingHeight;
        this.mDown = down;
        setDuration(duration);
    }

// -- Functions

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t)
    {
        int newHeight;
        if (mDown) {
            newHeight = (int) (((mEndingHeight - mStartingHeight) * interpolatedTime) + mStartingHeight);
        }
        else {
            newHeight = (int) (((mEndingHeight - mStartingHeight)* (1 - interpolatedTime)) + mStartingHeight);
        }
        mView.getLayoutParams().height = newHeight;
        mView.requestLayout();
    }

    @Override
    public void initialize(int width, int height, int parentWidth, int parentHeight) {
        super.initialize(width, height, parentWidth, parentHeight);
    }

    @Override
    public boolean willChangeBounds() {
        return true;
    }

// -- Constants

    // newHeight =  x * 0.25; oldHeight = newHeight * 4;
    public static final float COLLAPSE_HEIGHT_MULTIPLIER = 0.25f;
    public static final float EXPAND_HEIGHT_MULTIPLIER = 4f;

    public static final long DEFAULT_DURATION = 500;

// -- Variables
    private final View mView;
    private final boolean mDown;
    private final int mEndingHeight;
    private final int mStartingHeight;

}