_positions.isNotEmpty: ScrollController not attached to any scroll views. flutter

Unhandled Exception: 'package:flutter/src/widgets/scroll_controller.dart': Failed assertion: line 110 pos 12: '_positions.isNotEmpty': ScrollController not attached to any scroll views.
这个问题试了很多方法
终于在这个网站https://stackoverflow.com/questions/52296387/scrollcontroller-jumpto-scrollcontroller-not-attached-to-any-scroll-views看到解决的要点
问题是出在

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if (_scrollController.position.pixels == 0 && prePixels != 0) { _scrollController.jumpTo(prePixels); } prePixels = _scrollController.position.pixels;

我使用了上面的代码，（向上滑动后这部分UI不显示了，所以flutter就不渲染了，_scrollController也就不存在了），所以报错了。
解决方案是加一个判断，等向上滑动后UI不显示了，就不执行这部分代码就好了
上面那个网站给出了是 if (_scrollController.hasClients){}
增加后

if (_scrollController.hasClients) { if (_scrollController.position.pixels == 0 && prePixels != 0) { _scrollController.jumpTo(prePixels); } prePixels = _scrollController.position.pixels; }