vue2+html2canvas+js PDF实现试卷导出和打印功能

1.首先安装

import html2canvas from 'html2canvas';

import { jsPDF } from 'jspdf';

2.引入打印插件print.js

import Print from "@/assets/js/print";

Vue.use(Print)

// 打印类属性、方法定义
/* eslint-disable */
const Print = function (dom, options) {
    if (!(this instanceof Print)) return new Print(dom, options);

    this.options = this.extend({
        'noPrint': '.no-print'
    }, options);

    if ((typeof dom) === "string") {
        this.dom = document.querySelector(dom);
    } else {
        this.isDOM(dom)
        this.dom = this.isDOM(dom) ? dom : dom.$el;
    }

    this.init();
};
Print.prototype = {
    init: function () {
        var content = this.getStyle() + this.getHtml();
        this.writeIframe(content);
    },
    extend: function (obj, obj2) {
        for (var k in obj2) {
            obj[k] = obj2[k];
        }
        return obj;
    },

    getStyle: function () {
        var str = "",
            styles = document.querySelectorAll('style,link');
        for (var i = 0; i < styles.length; i++) {
            str += styles[i].outerHTML;
        }
        str += "<style>" + (this.options.noPrint ? this.options.noPrint : '.no-print') + "{display:none;}</style>";
        // str += "<style>html,body,div{height: auto!important;font-size:14px}</style>";
        return str;
    },

    getHtml: function () {
        var inputs = document.querySelectorAll('input');
        var textareas = document.querySelectorAll('textarea');
        var selects = document.querySelectorAll('select');

        for (var k = 0; k < inputs.length; k++) {
            if (inputs[k].type == "checkbox" || inputs[k].type == "radio") {
                if (inputs[k].checked == true) {
                    inputs[k].setAttribute('checked', "checked")
                } else {
                    inputs[k].removeAttribute('checked')
                }
            } else if (inputs[k].type == "text") {
                inputs[k].setAttribute('value', inputs[k].value)
            } else {
                inputs[k].setAttribute('value', inputs[k].value)
            }
        }

        for (var k2 = 0; k2 < textareas.length; k2++) {
            if (textareas[k2].type == 'textarea') {
                textareas[k2].innerHTML = textareas[k2].value
            }
        }

        for (var k3 = 0; k3 < selects.length; k3++) {
            if (selects[k3].type == 'select-one') {
                var child = selects[k3].children;
                for (var i in child) {
                    if (child[i].tagName == 'OPTION') {
                        if (child[i].selected == true) {
                            child[i].setAttribute('selected', "selected")
                        } else {
                            child[i].removeAttribute('selected')
                        }
                    }
                }
            }
        }
        return this.dom.outerHTML;
    },

    writeIframe: function (content) {
        var w, doc, iframe = document.createElement('iframe'),
            f = document.body.appendChild(iframe);
        iframe.id = "myIframe";
        //iframe.style = "position:absolute;width:0;height:0;top:-10px;left:-10px;";
        iframe.setAttribute('style', 'position:absolute;width:0;height:0;top:-10px;left:-10px;');
        w = f.contentWindow || f.contentDocument;
        doc = f.contentDocument || f.contentWindow.document;
        doc.open();
        doc.write(content);
        doc.close();
        var _this = this
        iframe.onload = function () {
            _this.toPrint(w);
            setTimeout(function () {
                document.body.removeChild(iframe)
            }, 100)
        }
    },

    toPrint: function (frameWindow) {
        try {
            setTimeout(function () {
                frameWindow.focus();
                try {
                    if (!frameWindow.document.execCommand('print', false, null)) {
                        frameWindow.print();
                    }
                } catch (e) {
                    frameWindow.print();
                }
                frameWindow.close();
            }, 10);
        } catch (err) {
            console.log('err', err);
        }
    },
    isDOM: (typeof HTMLElement === 'object') ?
        function (obj) {
            return obj instanceof HTMLElement;
        } :
        function (obj) {
            return obj && typeof obj === 'object' && obj.nodeType === 1 && typeof obj.nodeName === 'string';
        }
};
const MyPlugin = {}
MyPlugin.install = function (Vue, options) {
    // 4. 添加实例方法
    Vue.prototype.$print = Print
}
export default MyPlugin

3.执行函数

 // loding等待
    toLoding() {
      this.loading = this.$loading({
        lock: true,
        text: 'Loading',
        spinner: 'el-icon-loading',
        background: 'rgba(0, 0, 0, 0.7)'
      });
      // 导出按钮显示状态
      this.pdfIsShowData = false;
      // 展开所有节点
      let activeNames = [];
      for (let i = 0; i < Object.keys(this.dataAll).length; i++) {
        activeNames.push((i));
      }
      this.activeNames = activeNames;
      // 展开所有子节点
      if (this.$refs.collapse && this.$refs.collapse.length > 0) {
        this.$refs.collapse.forEach((item, index) => {
          item.activeNames = ['0'];
        })
      }
      // 关闭滚动条
      this.isMaxHeight = false;
    },
    // 打印试卷
    printPaper() {
      // 等待节点全部展开
      this.toLoding();
      setTimeout(() => {
        this.$nextTick(() => {
          this.$print(this.$refs.printContent);
          setTimeout(() => {
            this.loading.close();
            this.pdfIsShowData = true;
          }, 1000)
        });
      }, 2000)
    },
    // 导出试卷
    exportPaper() {
      // 等待节点全部展开
      this.toLoding()
      setTimeout(() => {
        this.$nextTick(() => {
          // 获取目标元素
          const element = document.querySelector('.toPdf');
          // 使用 html2canvas 捕获快照
          html2canvas(element).then(canvas => {
            // 将 canvas 转换为图片数据
            const imgData = canvas.toDataURL('image/png');
            // 创建一个 jsPDF 实例
            const pdf = new jsPDF('p', 'mm', 'a4');
            const imgWidth = 210; // A4纸宽
            const pageHeight = 297; // A4纸高
            let imgHeight = canvas.height * imgWidth / canvas.width;
            let heightLeft = imgHeight;

            // 添加图像到 PDF 第一页
            let position = 0;
            pdf.addImage(imgData, 'PNG', 0, position, imgWidth, imgHeight);
            heightLeft -= pageHeight;

            // 如果内容超过一页，则添加更多页
            while (heightLeft >= 0) {
              position = heightLeft - imgHeight;
              pdf.addPage();
              pdf.addImage(imgData, 'PNG', 0, position, imgWidth, imgHeight);
              heightLeft -= pageHeight;
            }
            // 下载 PDF 文件
            pdf.save(`${this.testName}.pdf`);
            this.pdfIsShowData = true
            this.loading.close();
            this.$message({
              message: '导出成功',
              type: 'success'
            });
            // 关闭滚动条
            this.isMaxHeight = false;
          }).catch(error => console.error('Error capturing the snapshot:', error));
        });
      }, 2000)
    },

4.样式问题

打印时候把所有字体颜色改为黑色

.toPdf-black * {
  color: #000 !important;
}

<div :class="{ 'toPdf': true, 'toPdf-black': !pdfIsShowData }" ref="printContent"