why can't i change the CardView_contentPadding?

[didadida-r]

i want to change the code of MaterialList, so i can freely change the padding of between the cards;
i try this in two way, but both fail.

1. I want to use the public way setContentPadding() to change the padding of cardview,
   but it don't work.
   LayoutInflater inflater = getLayoutInflater();
   CardLayout cardLayout = (CardLayout) inflater.inflate(R.layout.card_layout, null);
   cardView = (CardView) cardLayout.findViewById(R.id.cardView);
   if(cardView != null){
   Log.v(TAG, "not null");
   cardView.setContentPadding(0, 0, 0, 0);
   }

2. I change the Constants in the styleable, but it will return to original value as soon as i run the project

           public static final int CardView_contentPadding = 8;
   public static final int CardView_contentPaddingBottom = 12;
   public static final int CardView_contentPaddingLeft = 9;
   public static final int CardView_contentPaddingRight = 10;
   public static final int CardView_contentPaddingTop = 11;