wepy绘制雷达图

代码如下：

<style lang='less'>
  .radar-canvas2 {
    width: 690rpx;
    height: 420rpx;
  }
</style>
<template>
  <canvas class='radar-canvas2' canvas-id='radar-canvas'></canvas>
</template>
<script>
import wepy from 'wepy'
var windowW = wx.getSystemInfoSync().windowWidth

export default class RadarCanvas extends wepy.component {
  props = {
    source: {
      default: [
        {desc: '综合', value: 0},
        {desc: '思修法基', value: 0},
        {desc: '史纲', value: 0},
        {desc: '马原', value: 0},
        {desc: '毛中特', value: 0}
      ],
      type: Array
    }
  }
  data = {
    ctx: null,
    sideNum: 5,
    angle: 1.26,
    centerPointX: 345,
    centerPointY: 210,
    radius: 120
  }
  methods = {
    drawCanvas: () => {
      let ctx = wx.createCanvasContext('radar-canvas')
      this.sideNum = this.source.length
      this.angle = Math.PI * 2 / this.sideNum
      this.centerPointX = this.rpx(690 / 2)
      this.centerPointY = this.rpx(420 / 2)
      this.radius = this.rpx(120)
      this.$apply()
      this.drawPolygon(ctx)
      this.drawRib(ctx)
      this.addDataPoint(ctx)
      this.linePoint(ctx)
      ctx.draw(false)
    }
  }
  drawPolygon(ctx) {
    ctx.setLineDash([2, 2])
    ctx.setStrokeStyle('#E3E2E2')
    let r = this.rpx(30)
    for (let i = 1; i < 5; i++) {
      ctx.beginPath()
      let currR = r * i // 当前半径
      ctx.setFontSize(this.rpx(20))
      ctx.setFillStyle('#8E8C8B')
      ctx.setTextAlign('right')
      ctx.fillText(25 * (i - 1), this.centerPointX - 5, this.centerPointY - r * (i - 1) + this.rpx(10))
      //  最外面的是实线
      if (i === 4) {
        ctx.setLineDash()
      }
      for (let j = 0; j < this.sideNum; j++) {
        let x = this.centerPointX + currR * Math.cos(this.angle * j + Math.PI / 3.3)
        let y = this.centerPointY + currR * Math.sin(this.angle * j + Math.PI / 3.3)
        ctx.lineTo(x, y)
      }
      ctx.closePath()
      ctx.stroke()
    }
  }
  drawRib(ctx) {
    ctx.setLineDash([2, 2])  // 虚线
    ctx.setStrokeStyle('#E3E2E2')
    ctx.beginPath()
    for (let i = 0; i < this.sideNum; i++) {
      let x = this.centerPointX + this.radius * Math.cos(this.angle * i + Math.PI / 3.3)
      let y = this.centerPointY + this.radius * Math.sin(this.angle * i + Math.PI / 3.3)
      ctx.moveTo(this.centerPointX, this.centerPointY)
      ctx.lineTo(x, y)
      ctx.setFontSize(this.rpx(28))
      ctx.setFillStyle('#8E8C8B')
      switch (i) {
        case 0:
          ctx.setTextAlign('left')
          ctx.fillText(this.source[i].desc, x, y + 20)
          break
        case 1:
          ctx.setTextAlign('right')
          ctx.fillText(this.source[i].desc, x, y + 20)
          break
        case 2:
          ctx.setTextAlign('right')
          ctx.fillText(this.source[i].desc, x - 10, y)
          break
        case 3:
          ctx.setTextAlign('center')
          ctx.fillText(this.source[i].desc, x, y - 10)
          break
        case 4:
          ctx.setTextAlign('left')
          ctx.fillText(this.source[i].desc, x + 10, y)
          break
        default:
          break
      }
    }
    ctx.closePath()
    ctx.stroke()
  }
  addDataPoint(ctx) {
    ctx.setLineDash()
    for (let i = 0; i < this.sideNum; i++) {
      let x = this.centerPointX + this.radius * Math.cos(this.angle * i + Math.PI / 3.3) * this.source[i].value
      let y = this.centerPointY + this.radius * Math.sin(this.angle * i + Math.PI / 3.3) * this.source[i].value
      ctx.beginPath()
      ctx.arc(x, y, this.rpx(4), 0, 2 * Math.PI)
      ctx.setFillStyle('#47D891')
      ctx.fill()
      ctx.closePath()
    }
  }
  linePoint(ctx) {
    ctx.setStrokeStyle('#47D891')
    ctx.beginPath()
    for (var i = 0; i < this.sideNum; i++) {
      var x = this.centerPointX + this.radius * Math.cos(this.angle * i + Math.PI / 3.3) * this.source[i].value
      var y = this.centerPointY + this.radius * Math.sin(this.angle * i + Math.PI / 3.3) * this.source[i].value
      ctx.lineTo(x, y)
    }
    ctx.closePath()
    ctx.setFillStyle('rgba(37,212,129,0.25)')
    ctx.fill()
    ctx.stroke()
  }
  rpx(param) {
    return Number((windowW / 750 * param).toFixed(2))
  }
}
</script>

效果图如下：