Collapse and expand a view on Android with a clean animation

ViewVisibilityAnimator.java

import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.Animation;
import android.view.animation.Transformation;

public class ViewVisibilityAnimator {

    private static final String VISIBILITY = "VISIBILITY";

    public ViewVisibilityAnimator() {
    }

    public void saveState(View view, Bundle bundle) {
        if (bundle == null) {
            return;
        }
        bundle.putInt(VISIBILITY, view.getVisibility());
    }

    public void restoreState(View view, Bundle bundle) {
        if (bundle == null) {
            return;
        }
        view.setVisibility(bundle.getInt(VISIBILITY));
    }

    public void toggle(View view) {
        if (view.getVisibility() == View.VISIBLE) {
            collapse(view);
            return;
        }
        expand(view);
    }


    public void expand(final View v) {
        v.measure(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        final int targtetHeight = v.getMeasuredHeight();
        v.getLayoutParams().height = 0;
        v.setVisibility(View.VISIBLE);
        Animation a = new Animation() {
            @Override
            protected void applyTransformation(float interpolatedTime, Transformation t) {
                v.getLayoutParams().height = interpolatedTime == 1 ? ViewGroup.LayoutParams.WRAP_CONTENT : (int) (targtetHeight * interpolatedTime);
                v.requestLayout();
            }

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

        a.setDuration((int) (targtetHeight / v.getContext().getResources().getDisplayMetrics().density));
        v.startAnimation(a);
    }

    public void collapse(final View v) {
        final int initialHeight = v.getMeasuredHeight();
        Animation a = new Animation() {
            @Override
            protected void applyTransformation(float interpolatedTime, Transformation t) {
                if (interpolatedTime == 1) {
                    v.setVisibility(View.GONE);
                } else {
                    v.getLayoutParams().height = initialHeight - (int) (initialHeight * interpolatedTime);
                    v.requestLayout();
                }
            }
            @Override
            public boolean willChangeBounds() {
                return true;
            }
        };
        a.setDuration((int) (initialHeight / v.getContext().getResources().getDisplayMetrics().density));
        v.startAnimation(a);
    }
}