flutter - 如何在 flutter 的盒子周围创建虚线边框？

Question

我正在使用 flutter 在我的应用程序中构建一个盒子布局列表。我想要盒子周围的虚线边框。我已经使用 card 小部件来创建盒子。但是，如何在框周围设置虚线边框？

Answer 1

编辑

我已将它作为一个包添加到 pub .

现在，你需要做的就是

DottedBorder(
  color: Colors.black,
  gap: 3,
  strokeWidth: 1,
  child: FlutterLogo(size: 148),
)

工作解决方案 [过时]

喜欢 tomerpacific在 this answer 中说, Flutter 目前没有虚线边框的默认实现。

我昨天工作了一段时间，并能够使用 CustomPainter 提出解决方案。希望这对某人有所帮助。

将 DashedRect 添加到您的容器中，就像这样

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Container(
          height: 400,
          width: 300,
          color: Colors.black12,
          child: DashedRect(color: Colors.red, strokeWidth: 2.0, gap: 3.0,),
        ),
      ),
    );
  }
}

DashedRect.dart

import 'package:flutter/material.dart';
import 'dart:math' as math;

class DashedRect extends StatelessWidget {
  final Color color;
  final double strokeWidth;
  final double gap;

  DashedRect(
      {this.color = Colors.black, this.strokeWidth = 1.0, this.gap = 5.0});

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Padding(
        padding: EdgeInsets.all(strokeWidth / 2),
        child: CustomPaint(
          painter:
              DashRectPainter(color: color, strokeWidth: strokeWidth, gap: gap),
        ),
      ),
    );
  }
}

class DashRectPainter extends CustomPainter {
  double strokeWidth;
  Color color;
  double gap;

  DashRectPainter(
      {this.strokeWidth = 5.0, this.color = Colors.red, this.gap = 5.0});

  @override
  void paint(Canvas canvas, Size size) {
    Paint dashedPaint = Paint()
      ..color = color
      ..strokeWidth = strokeWidth
      ..style = PaintingStyle.stroke;

    double x = size.width;
    double y = size.height;

    Path _topPath = getDashedPath(
      a: math.Point(0, 0),
      b: math.Point(x, 0),
      gap: gap,
    );

    Path _rightPath = getDashedPath(
      a: math.Point(x, 0),
      b: math.Point(x, y),
      gap: gap,
    );

    Path _bottomPath = getDashedPath(
      a: math.Point(0, y),
      b: math.Point(x, y),
      gap: gap,
    );

    Path _leftPath = getDashedPath(
      a: math.Point(0, 0),
      b: math.Point(0.001, y),
      gap: gap,
    );

    canvas.drawPath(_topPath, dashedPaint);
    canvas.drawPath(_rightPath, dashedPaint);
    canvas.drawPath(_bottomPath, dashedPaint);
    canvas.drawPath(_leftPath, dashedPaint);
  }

  Path getDashedPath({
    @required math.Point<double> a,
    @required math.Point<double> b,
    @required gap,
  }) {
    Size size = Size(b.x - a.x, b.y - a.y);
    Path path = Path();
    path.moveTo(a.x, a.y);
    bool shouldDraw = true;
    math.Point currentPoint = math.Point(a.x, a.y);

    num radians = math.atan(size.height / size.width);

    num dx = math.cos(radians) * gap < 0
        ? math.cos(radians) * gap * -1
        : math.cos(radians) * gap;

    num dy = math.sin(radians) * gap < 0
        ? math.sin(radians) * gap * -1
        : math.sin(radians) * gap;

    while (currentPoint.x <= b.x && currentPoint.y <= b.y) {
      shouldDraw
          ? path.lineTo(currentPoint.x, currentPoint.y)
          : path.moveTo(currentPoint.x, currentPoint.y);
      shouldDraw = !shouldDraw;
      currentPoint = math.Point(
        currentPoint.x + dx,
        currentPoint.y + dy,
      );
    }
    return path;
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}

我不希望这适用于所有用例，并且有很大的定制和改进空间。如果您发现任何错误，请发表评论。