uniapp 微信小程序使用echarts

本文目的：通过分包的方式，尽可能在微信小程序中使用最新的echarts。
当然你也可以直接使用现成的uchart或者市场里别人封好的echarts.

准备工作
- 下载echarts-for-weixin源码。
  - 复制ec-canvas文件夹以及下属文件，在uniapp项目中与pages同级的地方创建wxcomponents文件夹，将复制的文件夹放于该文件夹下。wxcomponents文件名不可更改,参考：Uniapp小程序自定义组件支持
  - 修改pages.json文件，往globalStyle中添加"usingComponents": {"ec-canvas": "/wxcomponents/ec-canvas/ec-canvas"}。
  - 跑一下项目，这样会在ec-canvas下生成一个ec-canvas.vue，我自己试过来跑在浏览器上(h5)会生成，直接跑微信小程序不会生成。
  - 因ec-canvas下已经包含echarts文件，但版本可能不是最新的，想换新的可以去echarts github下载，至此准备工作完成。
修改ec-canvas.vue中的代码
- 替换两个canvas标签中所绑定的事件,视methods中的方法名而定
  - @touchstart=“touchStart”
  - @touchmove=“touchMove”
  - @touchend=“touchEnd”
- 去除import上的两行代码:global['__wxVueOptions'] = {components:{}}和global['__wxRoute'] = 'ec-canvas/ec-canvas'
- 确保echart.js文件的路径与名称是否引用正确,下载过来没改名可能是echarts.min.js
- 将export default global['__wxComponents']['ec-canvas/ec-canvas']改为export default {},然后将Component中的键按Vue的原本语法一一复制:
  - properties => props, 其中的value改为default
  - data => data() { return {} }
  - ready => mounted() {}
  - methods => 直接复制即可
  - compareVersion和wrapTouch这两个方法至于export default上即可,无需放在methods中
- 给methods的init方法加上async,在if (isUseNewCanvas)上加上await this.$nextTick()，否则具体的init方法中获取node会变成null。
- 在当前文件搜索this.data替换为this.
- 在当前文件搜索setData,将唯一一条this.setData({ isUseNewCanvas })改为this.isUseNewCanvas = isUseNewCanvas
- 改完后的ec-canvas.vue参考:

<template><uni-shadow-root class="ec-canvas-ec-canvas"><canvasv-if="isUseNewCanvas"type="2d"class="ec-canvas":canvas-id="canvasId"@init="init"@touchstart="touchStart"@touchmove="touchMove"@touchend="touchEnd"></canvas><canvasv-elseclass="ec-canvas":canvas-id="canvasId"@init="init"@touchstart="touchStart"@touchmove="touchMove"@touchend="touchEnd"></canvas></uni-shadow-root>
</template><script>
import WxCanvas from './wx-canvas'
import * as echarts from './echarts'let ctxfunction compareVersion(v1, v2) {v1 = v1.split('.')v2 = v2.split('.')const len = Math.max(v1.length, v2.length)while (v1.length < len) {v1.push('0')}while (v2.length < len) {v2.push('0')}for (let i = 0; i < len; i++) {const num1 = parseInt(v1[i])const num2 = parseInt(v2[i])if (num1 > num2) {return 1} else if (num1 < num2) {return -1}}return 0
}function wrapTouch(event) {for (let i = 0; i < event.touches.length; ++i) {const touch = event.touches[i]touch.offsetX = touch.xtouch.offsetY = touch.y}return event
}
export default {props: {canvasId: {type: String,value: 'ec-canvas',},ec: {type: Object,},forceUseOldCanvas: {type: Boolean,value: false,},},data() {return {isUseNewCanvas: false,}},onReady: function () {// Disable prograssive because drawImage doesn't support DOM as parameter// See https://developers.weixin.qq.com/miniprogram/dev/api/canvas/CanvasContext.drawImage.htmlecharts.registerPreprocessor((option) => {if (option && option.series) {if (option.series.length > 0) {option.series.forEach((series) => {series.progressive = 0})} else if (typeof option.series === 'object') {option.series.progressive = 0}}})if (!this.ec) {console.warn('组件需绑定 ec 变量，例：<ec-canvas id="mychart-dom-bar" ' +'canvas-id="mychart-bar" ec="{{ ec }}"></ec-canvas>')return}if (!this.ec.lazyLoad) {this.init()}},methods: {init: async function (callback) {const version = wx.getSystemInfoSync().SDKVersionconst canUseNewCanvas = compareVersion(version, '2.9.0') >= 0const forceUseOldCanvas = this.forceUseOldCanvasconst isUseNewCanvas = canUseNewCanvas && !forceUseOldCanvasthis.isUseNewCanvas = isUseNewCanvasif (forceUseOldCanvas && canUseNewCanvas) {console.warn('开发者强制使用旧canvas,建议关闭')}await this.$nextTick()if (isUseNewCanvas) {// console.log('微信基础库版本大于2.9.0，开始使用<canvas type="2d"/>');// 2.9.0 可以使用 <canvas type="2d"></canvas>this.initByNewWay(callback)} else {const isValid = compareVersion(version, '1.9.91') >= 0if (!isValid) {console.error('微信基础库版本过低，需大于等于 1.9.91。' +'参见：https://github.com/ecomfe/echarts-for-weixin' +'#%E5%BE%AE%E4%BF%A1%E7%89%88%E6%9C%AC%E8%A6%81%E6%B1%82')return} else {console.warn('建议将微信基础库调整大于等于2.9.0版本。升级后绘图将有更好性能')this.initByOldWay(callback)}}},initByOldWay(callback) {// 1.9.91 <= version < 2.9.0：原来的方式初始化ctx = wx.createCanvasContext(this.canvasId, this)const canvas = new WxCanvas(ctx, this.canvasId, false)echarts.setCanvasCreator(() => {return canvas})// const canvasDpr = wx.getSystemInfoSync().pixelRatio // 微信旧的canvas不能传入dprconst canvasDpr = 1var query = wx.createSelectorQuery().in(this)query.select('.ec-canvas').boundingClientRect((res) => {if (typeof callback === 'function') {this.chart = callback(canvas, res.width, res.height, canvasDpr)} else if (this.ec &&typeof this.ec.onInit === 'function') {this.chart = this.ec.onInit(canvas,res.width,res.height,canvasDpr)} else {this.triggerEvent('init', {canvas: canvas,width: res.width,height: res.height,canvasDpr: canvasDpr, // 增加了dpr，可方便外面echarts.init})}}).exec()},initByNewWay(callback) {// version >= 2.9.0：使用新的方式初始化const query = wx.createSelectorQuery().in(this)query.select('.ec-canvas').fields({ node: true, size: true }).exec((res) => {const canvasNode = res[0].nodethis.canvasNode = canvasNodeconst canvasDpr = wx.getSystemInfoSync().pixelRatioconst canvasWidth = res[0].widthconst canvasHeight = res[0].heightconst ctx = canvasNode.getContext('2d')const canvas = new WxCanvas(ctx, this.canvasId, true, canvasNode)echarts.setCanvasCreator(() => {return canvas})if (typeof callback === 'function') {this.chart = callback(canvas, canvasWidth, canvasHeight, canvasDpr)} else if (this.ec &&typeof this.ec.onInit === 'function') {this.chart = this.ec.onInit(canvas,canvasWidth,canvasHeight,canvasDpr)} else {this.triggerEvent('init', {canvas: canvas,width: canvasWidth,height: canvasHeight,dpr: canvasDpr,})}})},canvasToTempFilePath(opt) {if (this.isUseNewCanvas) {// 新版const query = wx.createSelectorQuery().in(this)query.select('.ec-canvas').fields({ node: true, size: true }).exec((res) => {const canvasNode = res[0].nodeopt.canvas = canvasNodewx.canvasToTempFilePath(opt)})} else {// 旧的if (!opt.canvasId) {opt.canvasId = this.canvasId}ctx.draw(true, () => {wx.canvasToTempFilePath(opt, this)})}},touchStart(e) {if (this.chart && e.touches.length > 0) {var touch = e.touches[0]var handler = this.chart.getZr().handlerhandler.dispatch('mousedown', {zrX: touch.x,zrY: touch.y,preventDefault: () => {},stopImmediatePropagation: () => {},stopPropagation: () => {},})handler.dispatch('mousemove', {zrX: touch.x,zrY: touch.y,preventDefault: () => {},stopImmediatePropagation: () => {},stopPropagation: () => {},})handler.processGesture(wrapTouch(e), 'start')}},touchMove(e) {if (this.chart && e.touches.length > 0) {var touch = e.touches[0]var handler = this.chart.getZr().handlerhandler.dispatch('mousemove', {zrX: touch.x,zrY: touch.y,preventDefault: () => {},stopImmediatePropagation: () => {},stopPropagation: () => {},})handler.processGesture(wrapTouch(e), 'change')}},touchEnd(e) {if (this.chart) {const touch = e.changedTouches ? e.changedTouches[0] : {}var handler = this.chart.getZr().handlerhandler.dispatch('mouseup', {zrX: touch.x,zrY: touch.y,preventDefault: () => {},stopImmediatePropagation: () => {},stopPropagation: () => {},})handler.dispatch('click', {zrX: touch.x,zrY: touch.y,preventDefault: () => {},stopImmediatePropagation: () => {},stopPropagation: () => {},})handler.processGesture(wrapTouch(e), 'end')}},},
}
</script>
<style scoped>
.ec-canvas {width: 100%;height: 100%;
}
</style>

将ec-canvas.vue、wx-canvas.js、echarts.js复制到需要使用的分包中，三个文件需在同一目录下，再在组件中引用即可，注意引用组件与echarts的路径：
- 复制完后，注意将wxcomponents 文件夹删除以及pages中对应的地方，否则主包体积会变大。
示例

<template><view style="height: 500rpx"><ec-canvasref="canvasRef"style="height:100%;width:100%;"canvas-id="mychart-bar":ec="{ onInit: initChart }"/></view>
</template><script>
import * as echarts from './components/echarts.min.js'
import EcCanvas from './components/ec-canvas'
let chartInstance
export default {components: {EcCanvas,},data() {return {}},mounted() {setTimeout(() => {this.setOption({series: [{data: [12, 20, 15, 8, 7, 11, 13],type: 'bar',},],})},3000)},methods: {initChart(canvas, width, height, dpr) {chartInstance = echarts.init(canvas, null, {width,height,devicePixelRatio: dpr, // 像素})canvas.setChart(chartInstance)chartInstance.setOption({xAxis: {type: 'category',data: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'],},yAxis: {type: 'value',},series: [{data: [120, 200, 150, 80, 70, 110, 130],type: 'bar',},],})return chartInstance},// 需要更新图表数据时调用setOption(data) {if(!chartInstance) returnchartInstance.setOption(data)}},
}
</script>