如何只向 d3 力定向图添加新节点？

Question

我使用 d3 创建了一个力导向图，它使用 useEffect 挂钩在 react 组件中呈现。该图最初呈现正确，但如果它是 re-rendered/updated 通过输入表单提交的新节点，则现有节点将被复制。

我原以为 .enter() 之后会保留现有节点，只会创建新节点，这显然不会发生。对我出错的地方有帮助吗？

编辑 1：这是输入的数据示例

var nodesData = [
{"id": "Do Something", "type": "activity"},
{"id": "My Document", "type": "object"}
]

这是图表的代码：

import React, { useRef, useEffect } from 'react';
import * as d3 from 'd3';
import '../../custom_styles/bpForceDirected.css';

interface IProps {
    data?: string;
    linkData?: string;
}

/* Component */
export const BpForceDirectedGraph = (props: IProps) => {

    const d3Container = useRef(null);

    /* The useEffect Hook is for running side effects outside of React,
       for instance inserting elements into the DOM using D3 */
    useEffect(
        () => {
            if (props.data && d3Container.current) {
                var w=500;
                var h=500;
                const svg = d3.select(d3Container.current)
                            .attr("viewBox", "0 0 " + w + " " + h )
                            .attr("preserveAspectRatio", "xMidYMid meet");

                var simulation = d3.forceSimulation()
                    .nodes(props.data);
                simulation
                    .force("charge_force", d3.forceManyBody())
                    .force("center_force", d3.forceCenter(w / 2, h / 2));

                function circleColor(d){
                    if(d.type ==="activity"){
                        return "blue";
                    } else {
                        return "pink";
                    }
                }

                function linkColor(d){
                    console.log(d); 
                    if(d.type === "Activity Output"){
                        return "green";
                    } else {
                        return "red";
                    }
                }

                //Create a node that will contain an object and text label      
                var node = svg.append("g")
                  .attr("class", "nodes")
                  .selectAll("g")
                  .data(props.data)
                  .enter()
                  .append("g");

                node.append("circle")
                        .attr("r", 10)
                        .attr("fill", circleColor);

                node.append("text")
                    .attr("class", "nodelabel")
                    .attr("dx", 12)
                    .attr("dy", ".35em")
                    .text(function(d) { return d.activityname });

                // The complete tickActions() function    
                function tickActions() {
                //update circle positions each tick of the simulation 
                    node.attr('transform', d => `translate(${d.x},${d.y})`);

                //update link positions 
                //simply tells one end of the line to follow one node around
                //and the other end of the line to follow the other node around
                    link
                        .attr("x1", function(d) { return d.source.x; })
                        .attr("y1", function(d) { return d.source.y; })
                        .attr("x2", function(d) { return d.target.x; })
                        .attr("y2", function(d) { return d.target.y; });
                }  

                  simulation.on("tick", tickActions );

                //Create the link force 
                //We need the id accessor to use named sources and targets 
                var link_force =  d3.forceLink(props.linkData)
                    .id(function(d) { return d.id; })

                simulation.force("links",link_force)

                //draw lines for the links 
                var link = svg.append("g")
                    .attr("class", "links")
                    .selectAll("line")
                    .data(props.linkData)
                    .enter().append("line")
                        .attr("stroke-width", 2)
                        .style("stroke", linkColor);

                // Remove old D3 elements
                node.exit()
                    .remove();
            }
        },

        [props.data, props.linkData, /*d3Container.current*/])

    return (
        <svg
            className="d3-component"
            ref={d3Container}
        />
    );
}

export default BpForceDirectedGraph;

编辑 2： Reproducible code example

Answer 1

出现这个问题是因为生成图表的函数在每次更新时被调用，并且没有考虑现有的内容。

这是解决问题的一种方法：

当（重新）定义变量 svg 时，在每次执行 useEffect 开始时清空 SVG。如下图，.html('')清空已有的SVG节点。

  const svg = d3
    .select(d3Container.current)
    .html("")
    .attr("viewBox", "0 0 " + w + " " + h)
    .attr("preserveAspectRatio", "xMidYMid meet");

一种更优雅的方法是更新代码，以便一个函数初始化图表，第二个函数（重新）生成图表，我对 React 的理解是，这是使用 componentDidMount 和componentDidUpdate.

如何只向 d3 力定向图添加新节点？

How to add only new nodes to d3 force directed graph?

d3.js

reactjs

d3-force-directed

use-effect