前端将html导出pdf文件解决分页问题-编程知识

这是借鉴了qq_251025116大佬的解决方案并优化升级完成的，原文链接

1.安装依赖

    npm install jspdf html2canvas

2.使用方法

    import htmlToPdffrom './index.js'const suc = () => {message.success('success');};//记得在需要打印的div上面添加 idlet dom = document.querySelector('#testPdf');let pdf = new htmlToPdf(dom, '测试', 'splitPages', ',', suc, 2);pdf.outPutPdfFn('测试');

3.使用说明

 //splitPages 是需要添加的类名，需要再那个地方分页就在那个地方添加类名 splitPages//如：<SpeciesIdentification class="splitPages" :baseData="baseData" /><SpeciesIdentificationSecond class="splitPages" :baseData="baseData" /><RepetPic class="splitPages" :baseData="baseData" /><RepetTable class="splitPages" :baseData="baseData" /><GeneralAnnotation class="splitPages" :baseData="baseData" />

导出效果：

在这里插入图片描述

具体代码：

import jsPDF from "jspdf";
import html2canvas from "html2canvas";/*
* 使用说明
* ele:需要导出pdf的容器元素(dom节点 不是id)
* pdfFileName: 导出文件的名字 通过调用outPutPdfFn方法也可传参数改变
* splitClassName: 避免分段截断的类名 当pdf有多页时需要传入此参数 , 避免pdf分页时截断元素  如表格<tr class="itemClass"></tr>
* breakClassName:自定义分页符类名，默认为break_page,添加改类名的标签被自动分页到下一页
* sucCallback：成功回调函数
* scale：增强图片清晰度 数字也打越清晰
* 调用方式 先 let pdf = new htmlToPdf(ele, 'pdf' ,'itemClass');
* 若想改变pdf名称 pdf.outPutPdfFn(fileName);  outPutPdfFn方法返回一个promise 可以使用then方法处理pdf生成后的逻辑
* */class htmlToPdf {constructor(ele, pdfFileName, splitClassName = "itemClass", breakClassName = "break_page", sucCallback = () => { }, scale = 2) {this.ele = ele;this.pdfFileName = pdfFileName;this.splitClassName = splitClassName;this.breakClassName = breakClassName;this.sucCallback = sucCallback;this.scale = scale;this.A4_WIDTH = 595;this.A4_HEIGHT = 842;this.pageHeight = 0this.pageNum = 1};async getPDF(resolve) {let ele = this.ele;let pdfFileName = this.pdfFileNamelet eleW = ele.offsetWidth // 获得该容器的宽let eleH = ele.scrollHeight // 获得该容器的高let eleOffsetTop = ele.offsetTop // 获得该容器到文档顶部的距离let eleOffsetLeft = ele.offsetLeft // 获得该容器到文档最左的距离let canvas = document.createElement("canvas")let abs = 0let win_in = document.documentElement.clientWidth || document.body.clientWidth // 获得当前可视窗口的宽度（不包含滚动条）let win_out = window.innerWidth // 获得当前窗口的宽度（包含滚动条）if (win_out > win_in) {abs = (win_out - win_in) / 2 // 获得滚动条宽度的一半} canvas.width = eleW * 2 // 将画布宽&&高放大两倍canvas.height = eleH * 2let context = canvas.getContext("2d")context.scale(this.scale, this.scale) // 增强图片清晰度context.translate(- eleOffsetLeft - abs, - eleOffsetTop)html2canvas(ele, {useCORS: true // 允许canvas画布内可以跨域请求外部链接图片, 允许跨域请求。}).then(async canvas => {let contentWidth = canvas.widthlet contentHeight = canvas.height// 一页pdf显示html页面生成的canvas高度;this.pageHeight = (contentWidth / this.A4_WIDTH) * this.A4_HEIGHT// 这样写的目的在于保持宽高比例一致 this.pageHeight/canvas.width = a4纸高度/a4纸宽度// 宽度和canvas.width保持一致// 未生成pdf的html页面高度let leftHeight = contentHeight// 页面偏移let position = 0// a4纸的尺寸[595,842],单位像素，html页面生成的canvas在pdf中图片的宽高let imgWidth = this.A4_WIDTH - 10 // -10为了页面有右边距let imgHeight = (this.A4_WIDTH / contentWidth) * contentHeightlet pageData = canvas.toDataURL("image/jpeg", 1.0)let pdf = jsPDF("", "pt", "a4");// 有两个高度需要区分，一个是html页面的实际高度，和生成pdf的页面高度(841.89)// 当内容未超过pdf一页显示的范围，无需分页if (leftHeight < this.pageHeight) { // 在pdf.addImage(pageData, 'JPEG', 左，上，宽度，高度)设置在pdf中显示；// pdf.addImage(pageData, "JPEG", 5, 0, imgWidth, imgHeight)pdf.addImage(pageData, 'JPEG', 6, 40, imgWidth - 12, imgHeight - 80);} else { // 分页while (leftHeight > 0) {pdf.addImage(pageData, "JPEG", 6, position + 40, imgWidth - 12, imgHeight - 80)leftHeight -= this.pageHeightposition -= this.A4_HEIGHT// 避免添加空白页if (leftHeight > 0) {pdf.addPage()}}} pdf.save(pdfFileName + ".pdf", { returnPromise: true }).then(() => { // 去除添加的空div 防止页面混乱let doms = document.querySelectorAll('.emptyDiv')for (let i = 0; i < doms.length; i++) {doms[i].remove();}});this.ele.style.height = '';this.sucCallback()resolve();})};// 输出pdfasync outPutPdfFn(pdfFileName) {return new Promise((resolve, reject) => { // 进行分割操作，当dom内容已超出a4的高度，则将该dom前插入一个空dom，把他挤下去，分割let target = this.ele;this.pageHeight = target.scrollWidth / this.A4_WIDTH * this.A4_HEIGHT;this.ele.style.height = 'initial';pdfFileName ? this.pdfFileName = pdfFileName : null;this.pageNum = 1; // pdf页数this.domEach(this.ele)// 异步函数，导出成功后处理交互this.getPDF(resolve, reject);})};domEach(dom) {let childNodes = dom.childNodeschildNodes.forEach((childDom, index) => {if (this.hasClass(childDom, this.splitClassName)) {let node = childDom;let eleBounding = this.ele.getBoundingClientRect();let bound = node.getBoundingClientRect();let offset2Ele = bound.top - eleBounding.toplet currentPage = Math.ceil((bound.bottom - eleBounding.top) / this.pageHeight); // 当前元素应该在哪一页if (this.pageNum < currentPage) {this.pageNum++let divParent = childDom.parentNode; // 获取该div的父节点let newNode = document.createElement('div');newNode.className = 'emptyDiv';newNode.style.background = 'white';newNode.style.height = (this.pageHeight * (this.pageNum - 1) - offset2Ele + 30) + 'px'; // +30为了在换下一页时有顶部的边距newNode.style.width = '100%';let next = childDom.nextSibling;// 获取div的下一个兄弟节点// 判断兄弟节点是否存在if (next) { // 存在则将新节点插入到div的下一个兄弟节点之前，即div之后divParent.insertBefore(newNode, node);} else { // 不存在则直接添加到最后,appendChild默认添加到divParent的最后divParent.appendChild(newNode);}}}if (this.hasClass(childDom, this.breakClassName)) {this.pageNum++console.log('break_page');let eleBounding = this.ele.getBoundingClientRect();let bound = childDom.getBoundingClientRect();let offset2Ele = bound.top - eleBounding.top// 剩余高度let alreadyHeight = offset2Ele % this.pageHeightlet remainingHeight = this.pageHeight - alreadyHeight + 20childDom.style.height = remainingHeight + 'px'}if (childDom.childNodes.length) {this.domEach(childDom)}})}hasClass(element, cls) {return (`` + element.className + ``).indexOf(`` + cls + ``) > -1;}
}export default htmlToPdf;