如何在Flutter中动态绘制一条从A点到B点的线

我解决了它 以下是解决方案

class TestDraw2Point extends StatefulWidget {
  @override
  _TestDraw2PointState createState() => _TestDraw2PointState();
}

class _TestDraw2PointState extends State<TestDraw2Point> {
  List<Offset> _points = [];

  void _addPoint(Offset point) {
    setState(() {
      _points.add(point);
      if (_points.length == 2) {
        _points = List.from(_points);
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Draw Line Example'),
      ),
      body: GestureDetector(
        onTapDown: (TapDownDetails details) {
          _addPoint(details.localPosition);
        },
        child: CustomPaint(
          painter: LinePainter(points: _points),
          child: Container(),
        ),
      ),
    );
  }
}

class LinePainter extends CustomPainter {
  List<Offset> points;

  LinePainter({required this.points});

  @override
  void paint(Canvas canvas, Size size) {
    if (points.length == 2) {
      final paint = Paint()
        ..color = Colors.black
        ..strokeWidth = 3.0;

      canvas.drawLine(points[0], points[1], paint);
    }
  }

  @override
  bool shouldRepaint(LinePainter oldDelegate) => true;
}

这里是绘制多线的另一个版本

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

  @override
  _DrawLineScreenState createState() => _DrawLineScreenState();
}

class _DrawLineScreenState extends State<DrawLineScreen> {
  final List<Offset> _points = [];
  final List<List<Offset>> _lines = [];

  void _addPoint(Offset point) {
    setState(() {
      _points.add(point);
      if (_points.length == 2) {
        _lines.add(List.from(_points));
        _points.clear();
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Draw Line Example'),
      ),
      body: GestureDetector(
        onTapDown: (TapDownDetails details) {
          _addPoint(details.localPosition);
        },
        child: CustomPaint(
          painter: LinePainter(lines: _lines, currentPoints: _points),
          child: Container(),
        ),
      ),
    );
  }
}

class LinePainter extends CustomPainter {
  List<List<Offset>> lines;
  List<Offset> currentPoints;

  LinePainter({required this.lines, required this.currentPoints});

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = Colors.black
      ..strokeWidth = 3.0;

    for (final line in lines) {
      canvas.drawLine(line[0], line[1], paint);
    }

    if (currentPoints.length == 2) {
      canvas.drawLine(currentPoints[0], currentPoints[1], paint);
    }
  }

  @override
  bool shouldRepaint(LinePainter oldDelegate) => true;
}