Flutter图形布局插件dart_dagre的使用

Flutter图形布局插件dart_dagre的使用

在Flutter开发中，有时我们需要对复杂的图形进行布局管理。dart_dagre 是 dagre.js 的 Dart 移植版本，可以帮助开发者轻松实现图形布局。本文将详细介绍如何在 Flutter 中使用 dart_dagre 插件，并通过一个完整的示例展示其功能。

安装 dart_dagre

首先，在项目的 pubspec.yaml 文件中添加 dart_dagre 依赖：

dependencies:
  dart_dagre: ^0.1.0

然后运行以下命令以安装依赖：

flutter pub get

使用 dart_dagre 进行图形布局

1. 创建图结构

dart_dagre 提供了强大的图结构创建能力。我们可以使用它来定义节点和边的关系。

import 'package:dart_dagre/dart_dagre.dart';

void main() {
  // 创建一个新的图
  var g = new dagre.graphlib.Graph()
    ..setGraph({})
    ..setDefaultEdgeLabel(() => {});

  // 添加节点
  g.setNode("A", {});
  g.setNode("B", {});
  g.setNode("C", {});
  g.setNode("D", {});

  // 添加边
  g.setEdge("A", "B", {});
  g.setEdge("B", "C", {});
  g.setEdge("C", "D", {});
}

2. 计算布局

dart_dagre 提供了 dagre.layout() 方法，可以自动计算节点的位置。

// 计算布局
var layout = new dagre.layout();
layout.run(g);

3. 渲染图形

为了在 Flutter 中渲染图形，我们可以使用 CustomPainter 来绘制节点和边。

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

class DagreGraph extends StatelessWidget {
  final dagre.graphlib.Graph graph;

  DagreGraph({required this.graph});

  [@override](/user/override)
  Widget build(BuildContext context) {
    return CustomPaint(
      size: Size(800, 600),
      painter: GraphPainter(graph),
    );
  }
}

class GraphPainter extends CustomPainter {
  final dagre.graphlib.Graph graph;

  GraphPainter(this.graph);

  [@override](/user/override)
  void paint(Canvas canvas, Size size) {
    var bounds = graph.graph().get('width', 'height');
    var renderer = dagre.renderers.RenderCanvas(canvas);

    // 绘制节点和边
    for (var v in graph.nodes()) {
      var node = graph.node(v);
      renderer.drawNode(node);
    }

    for (var e in graph.edges()) {
      var edge = graph.edge(e);
      renderer.drawEdge(edge);
    }
  }

  [@override](/user/override)
  bool shouldRepaint(covariant CustomPainter oldDelegate) => false;
}

4. 整合到应用中

最后，我们将上述代码整合到 Flutter 应用中，展示图形布局效果。

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

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text("dart_dagre 示例")),
        body: Center(
          child: DagreGraph(graph: createGraph()),
        ),
      ),
    );
  }

  dagre.graphlib.Graph createGraph() {
    var g = new dagre.graphlib.Graph()
      ..setGraph({})
      ..setDefaultEdgeLabel(() => {});

    g.setNode("A", {});
    g.setNode("B", {});
    g.setNode("C", {});
    g.setNode("D", {});

    g.setEdge("A", "B", {});
    g.setEdge("B", "C", {});
    g.setEdge("C", "D", {});

    var layout = new dagre.layout();
    layout.run(g);

    return g;
  }
}

更多关于Flutter图形布局插件dart_dagre的使用的实战教程也可以访问 https://www.itying.com/category-92-b0.html

1 回复

更多关于Flutter图形布局插件dart_dagre的使用的实战系列教程也可以访问 https://www.itying.com/category-92-b0.html


dart_dagre 是一个用于在 Flutter 中绘制有向无环图（DAG）的插件。它基于 dagre 库，允许你创建和布局复杂的图形结构，并在 Flutter 中渲染它们。dart_dagre 提供了节点和边的布局功能，并且可以与 Flutter 的 CustomPaint 或 Canvas 结合使用来绘制图形。

安装 dart_dagre

首先，你需要在 pubspec.yaml 文件中添加 dart_dagre 依赖：

dependencies:
  flutter:
    sdk: flutter
  dart_dagre: ^0.1.0

然后运行 flutter pub get 来安装依赖。

使用 dart_dagre

以下是一个简单的示例，展示如何使用 dart_dagre 来创建和布局一个简单的有向无环图，并在 Flutter 中绘制它。

import 'package:flutter/material.dart';
import 'package:dart_dagre/dart_dagre.dart';

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

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Dart Dagre Example')),
        body: DagreGraph(),
      ),
    );
  }
}

class DagreGraph extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    // 创建一个有向无环图
    final graph = Graph()
      ..setGraph({})
      ..setDefaultEdgeLabel(() => {});

    // 添加节点
    graph.setNode('A', {'label': 'Node A', 'width': 100, 'height': 50});
    graph.setNode('B', {'label': 'Node B', 'width': 100, 'height': 50});
    graph.setNode('C', {'label': 'Node C', 'width': 100, 'height': 50});

    // 添加边
    graph.setEdge('A', 'B');
    graph.setEdge('B', 'C');

    // 布局图形
    final layout = Layout()..run(graph);

    // 获取节点和边的布局信息
    final nodes = graph.nodes.map((node) => graph.node(node)).toList();
    final edges = graph.edges.map((edge) => graph.edge(edge)).toList();

    return CustomPaint(
      size: Size(300, 300),
      painter: DagrePainter(nodes: nodes, edges: edges),
    );
  }
}

class DagrePainter extends CustomPainter {
  final List<Node> nodes;
  final List<Edge> edges;

  DagrePainter({required this.nodes, required this.edges});

  [@override](/user/override)
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = Colors.blue
      ..style = PaintingStyle.fill;

    // 绘制节点
    for (final node in nodes) {
      final rect = Rect.fromLTWH(node.x, node.y, node.width, node.height);
      canvas.drawRect(rect, paint);

      // 绘制节点标签
      final textPainter = TextPainter(
        text: TextSpan(
          text: node.label,
          style: TextStyle(color: Colors.white, fontSize: 14),
        ),
        textDirection: TextDirection.ltr,
      );
      textPainter.layout();
      textPainter.paint(
        canvas,
        Offset(node.x + (node.width - textPainter.width) / 2,
            node.y + (node.height - textPainter.height) / 2),
      );
    }

    // 绘制边
    final linePaint = Paint()
      ..color = Colors.black
      ..strokeWidth = 2
      ..style = PaintingStyle.stroke;

    for (final edge in edges) {
      final points = edge.points;
      if (points.isNotEmpty) {
        final path = Path();
        path.moveTo(points[0].x, points[0].y);
        for (var i = 1; i < points.length; i++) {
          path.lineTo(points[i].x, points[i].y);
        }
        canvas.drawPath(path, linePaint);
      }
    }
  }

  [@override](/user/override)
  bool shouldRepaint(covariant CustomPainter oldDelegate) {
    return false;
  }
}
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