Flutter Web中SelectionArea嵌套PageView异常：是Bug还是可规避？

场景1：SelectionArea作为PageView父组件 #

当SelectionArea包裹PageView时，即便给PageView设置了physics: const NeverScrollableScrollPhysics()，选中文本后拖动仍能触发PageView的横向滑动，同时会随机抛出非100%复现的断言错误：

globalRect.size.height >= _dragTargetRelatedToScrollOrigin.size.height
"Drag target size is larger than scrollable size, which may cause bouncing"

复现代码 #

void main() {
  runApp(
    const MyApp(),
  );
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: SelectionArea(child: PageViewBug()),
    );
  }
}

class PageViewBug extends StatefulWidget {
  const PageViewBug({super.key});

  @override
  State<PageViewBug> createState() => _PageViewBugState();
}

class _PageViewBugState extends State<PageViewBug> {
  final PageController controllerH = PageController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('PageViewBug')),
      body: PageView(
        controller: controllerH,
        physics: const NeverScrollableScrollPhysics(),
        scrollDirection: Axis.horizontal,
        children: const [
          Center(child: Text("Page1")),
          Center(child: Text("Page2")),
          Center(child: Text("Page3")),
        ],
      ),
    );
  }
}

场景2：SelectionArea下移至PageView子页面层级 #

调整Widget树结构，将SelectionArea放在PageView的每个子页面组件上方，结构如下：

-MaterialApp
--Scaffold
---BlocBuilder
----PageView
-----SelectionArea(Screen1)
-----SelectionArea(Screen2)

此时拖动选中文本移出屏幕时，会频繁抛出相同的断言异常：

Error: Assertion failed: file:///D:/..../flutter/packages/flutter/lib/src/widgets/scrollable_helpers.dart:237:7
globalRect.size.width >= _dragTargetRelatedToScrollOrigin.size.width &&
globalRect.size.height >= _dragTargetRelatedToScrollOrigin.size.height
"Drag target size is larger than scrollable size, which may cause bouncing"

问题分析 #

这大概率是Flutter框架的内部Bug：SelectionArea的文本选择拖动手势逻辑与PageView这类Scrollable组件的手势处理存在冲突，框架内部的断言校验（用于防止滚动区域异常）在文本拖动超出组件尺寸时被触发，而NeverScrollableScrollPhysics无法完全拦截文本选择带来的滚动触发。

临时解决方案 #

1. 调整Widget层级：尽量将SelectionArea仅包裹需要文本选择的局部容器，避免直接嵌套PageView这类可滚动组件
2. 手势拦截：给PageView添加GestureDetector，拦截横向拖动手势，避免文本选择拖动触发页面滚动
3. 跟进官方修复：可以在Flutter官方Issue仓库搜索相关问题，提交复现案例，等待框架层面的修复

内容的提问来源于stack exchange，提问作者Fabian M