This time I will show you how to use Vue canvas to implement the mobile handwriting pad function, and what are the precautions for using Vue canvas to implement the mobile handwriting pad function. The following is a practical case, let’s take a look. .
<template> <p class="hello"> <!--touchstart,touchmove,touchend,touchcancel 这--> <button type="" v-on:click="clear">清除</button> <button v-on:click="save">保存</button> <canvas id="canvas" width="300" height="600" style="border:1px solid black">Canvas画板</canvas> <img v-bind:src="url" alt=""> </p> </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>
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