Vue利用canvas实现移动端手写板的方法

<template> <div> <!--touchstart,touchmove,touchend,touchcancel 这--> <button type="" v-on:click="clear">清除</button> <button v-on:click="save">保存</button> <canvas>Canvas画板</canvas> <img v-bind:src="url" alt=""> </div> </template> <script> var draw; var preHandler = function(e){e.preventDefault();} class Draw { constructor(el) { this.el = el this.canvas = document.getElementById(this.el) this.cxt = this.canvas.getContext('2d') this.stage_info = canvas.getBoundingClientRect() this.path = { beginX: 0, beginY: 0, endX: 0, endY: 0 } } init(btn) { var that = this; this.canvas.addEventListener('touchstart', function(event) { document.addEventListener('touchstart', preHandler, false); that.drawBegin(event) }) this.canvas.addEventListener('touchend', function(event) { document.addEventListener('touchend', preHandler, false); that.drawEnd() }) this.clear(btn) } drawBegin(e) { var that = this; window.getSelection() ? window.getSelection().removeAllRanges() : document.selection.empty() this.cxt.strokeStyle = "#000" this.cxt.beginPath() this.cxt.moveTo( e.changedTouches[0].clientX - this.stage_info.left, e.changedTouches[0].clientY - this.stage_info.top ) this.path.beginX = e.changedTouches[0].clientX - this.stage_info.left this.path.beginY = e.changedTouches[0].clientY - this.stage_info.top canvas.addEventListener("touchmove",function(){ that.drawing(event) }) } drawing(e) { this.cxt.lineTo( e.changedTouches[0].clientX - this.stage_info.left, e.changedTouches[0].clientY - this.stage_info.top ) this.path.endX = e.changedTouches[0].clientX - this.stage_info.left this.path.endY = e.changedTouches[0].clientY - this.stage_info.top this.cxt.stroke() } drawEnd() { document.removeEventListener('touchstart', preHandler, false); document.removeEventListener('touchend', preHandler, false); document.removeEventListener('touchmove', preHandler, false); //canvas.ontouchmove = canvas.ontouchend = null } clear(btn) { this.cxt.clearRect(0, 0, 300, 600) } save(){ return canvas.toDataURL("image/png") } } export default { data () { return { msg: 'Welcome to Your Vue.js App', val:true, url:"" } }, mounted() { draw=new Draw('canvas'); draw.init(); }, methods:{ clear:function(){ draw.clear(); }, save:function(){ var data=draw.save(); this.url = data; console.log(data) }, 　　　mutate(word) { this.$emit("input", word); }, } } </script> <!-- Add "scoped" attribute to limit CSS to this component only --> <style scoped> h1, h2 { font-weight: normal; } ul { list-style-type: none; padding: 0; } li { display: inline-block; margin: 0 10px; } a { color: #42b983; } #canvas { background: pink; cursor: default; } #keyword-box { margin: 10px 0; } </style>