ExpandAnimation.java

package com.avinash.uihelper;

import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;

public class ExpandAnimation extends Animation {
        private int baseHeight;
        private int delta;
        private View view;
        private GroupInfo groupInfo;

        ExpandAnimation(View v, int startHeight, int endHeight, GroupInfo info) {
            baseHeight = startHeight;
            delta = endHeight - startHeight;
            view = v;
            groupInfo = info;

            view.getLayoutParams().height = startHeight;
            view.requestLayout();
        }

        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
            super.applyTransformation(interpolatedTime, t);
            if (interpolatedTime < 1.0f) {
                int val = baseHeight + (int) (delta * interpolatedTime);
                view.getLayoutParams().height = val;
                groupInfo.dummyHeight = val;
                view.requestLayout();
            } else {
                int val = baseHeight + delta;
                view.getLayoutParams().height = val;
                groupInfo.dummyHeight = val;
                view.requestLayout();
            }
        }
    }