展开和折叠视图的动画

public class ViewAnimationUtils {
        
        public static void expand(final View v) {
            v.measure(LayoutParams.MATCH_PARENT, 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
                            ? 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 static 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);
        }
    }