flutter - 我如何通过拖动它们来选择小部件，但也可以在 flutter 中单独单击它们？

Question

我想创建一个可以在多个区域上拖动手指的界面。这会将区域的状态更改为选定状态(参见图片)。

解决这个问题的最佳方法是什么？

起始位置:

开始拖动:

选择第一个区域:

选定的所有区域:

Answer 1

代码需要针对当前的 Flutter/Dart 版本进行一些更新，但是 this为我工作。

更新代码:

    import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(primarySwatch: Colors.blue),
      home: Grid(),
    );
  }
}

class Grid extends StatefulWidget {
  @override
  GridState createState() {
    return new GridState();
  }
}

class GridState extends State<Grid> {
  final Set<int> selectedIndexes = Set<int>();
  final key = GlobalKey();
  final Set<_Foo> _trackTaped = Set<_Foo>();

  _detectTapedItem(PointerEvent event) {
    final RenderBox box = key.currentContext!.findAncestorRenderObjectOfType<RenderBox>()!;
    final result = BoxHitTestResult();
    Offset local = box.globalToLocal(event.position);
    if (box.hitTest(result, position: local)) {
      for (final hit in result.path) {
        /// temporary variable so that the [is] allows access of [index]
        final target = hit.target;
        if (target is _Foo && !_trackTaped.contains(target)) {
          _trackTaped.add(target);
          _selectIndex(target.index);
        }
      }
    }
  }

  _selectIndex(int index) {
    setState(() {
      selectedIndexes.add(index);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Listener(
      onPointerDown: _detectTapedItem,
      onPointerMove: _detectTapedItem,
      onPointerUp: _clearSelection,
      child: GridView.builder(
        key: key,
        itemCount: 6,
        physics: NeverScrollableScrollPhysics(),
        gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
          crossAxisCount: 3,
          childAspectRatio: 1.0,
          crossAxisSpacing: 5.0,
          mainAxisSpacing: 5.0,
        ),
        itemBuilder: (context, index) {
          return Foo(
            index: index,
            child: Container(
              color: selectedIndexes.contains(index) ? Colors.red : Colors.blue,
            ),
          );
        },
      ),
    );
  }

  void _clearSelection(PointerUpEvent event) {
    _trackTaped.clear();
    setState(() {
      selectedIndexes.clear();
    });
  }
}

class Foo extends SingleChildRenderObjectWidget {
  final int index;

  Foo({required Widget child, required this.index, Key? key}) : super(child: child, key: key);

  @override
  _Foo createRenderObject(BuildContext context) {
    return _Foo(index);
  }

  @override
  void updateRenderObject(BuildContext context, _Foo renderObject) {
    renderObject..index = index;
  }
}

class _Foo extends RenderProxyBox {
  int index;
  _Foo(this.index);
}