transform abstract method

Widget transform(
  1. int index,
  2. double page,
  3. double aniValue,
  4. Widget child,
) 
 if (page == index) {
    /// 静止状态
  } else if (page > index) {
      <---- n+1页面出来 (index = n ; aniValue  1-0)
      -----> n-1页面出来 (index = n-1 ; aniValue  0-1)
  } else {
      <---- n+1页面出来 (index = n+1 ; aniValue  0-1)
      -----> n-1页面出来 (index = n ; aniValue  1-0)
  }

Implementation

Widget transform(int index, double page, double aniValue, Widget child);