Flutter-AzListView

修复数据过少时跳转反弹

修改源码中滚动代码如下所示。

void _scrollTopIndex(String tag) {
  int index = _getIndex(tag);
  int itemsCountOnScreen = itemPositionsListener.itemPositions.value.length;
  if (index != -1) {
    //如果要跳转的条目后面的数据个数<屏幕可容纳的数据个数,使用align属性去调整跳转
    //条目在屏幕上的位置。align默认是0，即条目的头部top与可视部分上边缘对齐。
    //计算正确的对齐位置，才能让它正常显示。

    //if the the items'counts after the item you want to jump less than
    //full screen items counts, use the align to justify the item's location
    // to be correct. The align defaults to be 0, which means the item's top
    // to align the view's top.
    /ange the data of alignment and make it show properly.
    if ((widget.data.length - index) < itemsCountOnScreen) {
      //可视口由两部分组成，一个是其它数据，一个是期望数据（即想要跳转却不足以填充屏幕的数据）。
      //用其他数据个数/总数据个数，作为alignment，就可以让期望数据正确对齐而不发生反弹。

      //The view port includes other datas and expected datas(this refers to
      //the data you want to jump but can't fill the screen and therefor causes
      //out bouncing).
      //other datas' length / all datas'length = alignment(the correct rete to align expected datas)
      double alignment = (itemsCountOnScreen - (widget.data.length - index)) /
          itemsCountOnScreen;
      itemScrollController.jumpTo(alignment: alignment, index: index);
    } else {
      itemScrollController.jumpTo(index: index);
    }
  }
}