uniapp封装小程序雷达图组件实现

效果图：

view

<canvas id="radar-canvas" class="radar-canvas" type="2d"></canvas>

style

.radar-canvas
    width 550rpx
    height 550rpx
    margin 0 auto

script

<script>
    import { toRpx } from "@/utils/common"

    const numCount = 5  //元素个数
    const numSlot = 4  //一条线上的总节点数
    const mW = toRpx(275) //Canvas的宽度
    const mCenter = mW / 2 //中心点
    const mAngle = Math.PI * 2 / numCount //角度
    const mRadius = mCenter - toRpx(43) //半径(减去的值用于给绘制的文本留空间)

    let canvas = null // canvas
    let canvasCtx = null // canvas context

    export default {
        name: 'RadarChart',
        props: {
        },
        methods: {
            // 初始化雷达图，在组件挂载的时候执行
            initDrawRadar() {
                console.log('init')
                const query = uni.createSelectorQuery().in(this)
                query.select('#radar-canvas').fields({ node: true, size: true }).exec((res) => {
                    canvas = res[0].node
                    canvasCtx = canvas.getContext('2d')
                    const dpr = uni.getSystemInfoSync().pixelRatio
                    canvas.width = res[0].width * dpr
                    canvas.height = res[0].height * dpr
                    canvasCtx.scale(dpr, dpr)
                })
            },
            // 开始执行绘制
            handleDraw(radarData) {
                this.drawEdge()
                this.drawLinePoint()
                this.drawText(radarData)
                this.drawSubText(radarData)
                this.drawEdgeDot()
                this.drawRegion(radarData, 'rgba(255, 105, 81, 0.4)')
            },
            // 绘制圆边
            drawEdge() {
                canvasCtx.strokeStyle = '#EEEEEE'
                for (let i = 0; i < numSlot; i++) {
                    // 计算半径
                    let radius = mRadius / numSlot * (i + 1)
                    if (i === 3) {
                        canvasCtx.lineWidth = toRpx(4)  // 设置线宽
                        canvasCtx.beginPath()
                        canvasCtx.arc(mCenter, mCenter, radius, 0, 2 * Math.PI,) // 开始画圆
                        canvasCtx.stroke()
                    } else {
                        canvasCtx.lineWidth = toRpx(1)
                        const space = 60 + 10 * (i+1)
                        this.drawDashCircle(mCenter, mCenter, radius, space)
                    }
                }
            },
            // 绘制外边框圆点
            drawEdgeDot(x, y) {
                canvasCtx.fillStyle = '#EEEEEF'
                canvasCtx.beginPath()
                for (let k = 0; k < numCount; k++) {
                    let x = mCenter + mRadius * Math.cos(mAngle * k - Math.PI / 2)
                    let y = mCenter + mRadius * Math.sin(mAngle * k - Math.PI / 2)
                    canvasCtx.arc(x, y, toRpx(5), Math.PI * 2, 0, true)
                    canvasCtx.closePath()
                }
                canvasCtx.fill()
            },
            // 绘制虚线圆
            drawDashCircle(x, y, radius, space = 100) {
                const gap = 2 * Math.PI / space
                canvasCtx.lineCap ='square'

                let start = 0; //从原点开始画
                while (start <= 2 * Math.PI) {
                    let end = start + gap
                    canvasCtx.beginPath() //开始一个新的路径
                    canvasCtx.arc(x, y, radius, start, end, false)
                    start = gap + end
                    canvasCtx.stroke() //对当前路径进行描边
                }
            },
            // 绘制连接点
            drawLinePoint() {
                canvasCtx.lineWidth = toRpx(1)
                canvasCtx.beginPath()
                for (let k = 0; k < numCount; k++) {
                    let x = mCenter + mRadius * Math.cos(mAngle * k - Math.PI / 2)
                    let y = mCenter + mRadius * Math.sin(mAngle * k - Math.PI / 2)
                    canvasCtx.moveTo(mCenter, mCenter)
                    canvasCtx.lineTo(x, y)
                }
                canvasCtx.stroke()
            },
            // 绘制文本信息
            drawText(mData) {
                canvasCtx.fillStyle = '#222325'
                canvasCtx.font = `bold ${toRpx(14)}px PingFangSC-Medium, PingFang SC`  //设置字体
                for (let n = 0; n < numCount; n++) {
                    let x = mCenter + mRadius * Math.cos(mAngle * n -  Math.PI / 2)
                    let y = mCenter + mRadius * Math.sin(mAngle * n -  Math.PI / 2)
                    //通过不同的位置，调整文本的显示位置
                    const text = mData[n][0]
                    if (n === 0) {
                        canvasCtx.fillText(text, x - toRpx(12), y - toRpx(30))
                    }
                    if (n === 1) {
                        canvasCtx.fillText(text, x + toRpx(12), y)
                    }
                    if (n === 2) {
                        canvasCtx.fillText(text, x + toRpx(12), y + toRpx(20))
                    }
                    if (n === 3) {
                        canvasCtx.fillText(text, x - toRpx(36), y + toRpx(20))
                    }
                    if (n === 4) {
                        canvasCtx.fillText(text, x - toRpx(40), y)
                    }
                }
            },
            // 绘制文本信息
            drawSubText(mData) {
                canvasCtx.fillStyle = '#8D949B'
                canvasCtx.font = `${toRpx(11)}px PingFangSC-Medium, PingFang SC`  //设置字体
                for (let n = 0; n < numCount; n++) {
                    const x = mCenter + mRadius * Math.cos(mAngle * n -  Math.PI / 2)
                    const y = mCenter + mRadius * Math.sin(mAngle * n -  Math.PI / 2)
                    //通过不同的位置，调整文本的显示位置
                    const text = `(${mData[n][1]})`
                    if (n === 0) {
                        canvasCtx.fillText(text, x - canvasCtx.measureText(text).width / 2, y - toRpx(10))
                    }
                    if (n === 1) {
                        canvasCtx.fillText(text, x + canvasCtx.measureText(text).width, y + toRpx(16))
                    }
                    if (n === 2) {
                        canvasCtx.fillText(text, x + canvasCtx.measureText(text).width - toRpx(4), y + toRpx(40))
                    }
                    if (n === 3) {
                        canvasCtx.fillText(text, x - canvasCtx.measureText(text).width - toRpx(12), y + toRpx(40))
                    }
                    if (n === 4) {
                        canvasCtx.fillText(text, x - canvasCtx.measureText(text).width - toRpx(16), y + toRpx(16))
                    }
                }
            },
            //绘制红色数据区域(数据和填充颜色)
            drawRegion(mData, color){
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            },
        },
        mounted() {
            this.initDrawRadar()
        }
    }
</script>

要注意的点是，这里是封装成组件调用，在初始化的时候，const query = uni.createSelectorQuery().in(this)，要加上in(this)，否则会报找不到node节点的错误信息

toRpx方法是将数字大小转化为rpx响应式单位大小，方法如下：

export function toRpx(val) {
    const res = uni.getSystemInfoSync()
    const scaleRate = res.windowWidth / 375
    return val * scaleRate
}

在页面中调用

<template>
    <!--雷达图-->
    <radar-chart :radarData="radarData" ref="radarRef"></radar-chart>
</template>

import RadarChart from './components/radar' 

export default {
    components: {
        RadarChart,
    },
    data() {
        return {
            radarData:[["听力", 0], ["口语",0], ["语法",0], ["词汇",0], ["阅读",0]],
        }
    },
    methods: {
        getData() {
            // 请求数据返回后，调用组件方法渲染
            this.$refs.radarRef.handleDraw(this.radarData)
        }
    }
}

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