记一次react-hooks项目获取图表图片集合并生成pdf的需求

需求: 获取子组件中所有图片的dom元素并生成图片,再把生成的图片转化为pdf下载

• 难点

  1. 众所周知,react是单向数据流,倡导f(data)⇒ UI的哲学, 并不建议过多直接操作dom,但是生成图片的base64格式时使用的ant design charts 要求必须获取ref才可以

  2. 逻辑流转如下图, 兄弟组件b发出按钮click事件后告知a组件去收集自身组件内图标的ref,由于是兄弟组件通信,此处借助了react-redux

     

  3. a组件获取所有图标ref

     const myRef = useRef()
     
     //每个组件类似于此:
     <BoxPlot ref={handleRefCallback}/>
     
     const handleRefCallback = React.useCallback((dom) => {
           handleRefs(dom)
     }, [])   //此处通过回调来获取ref
     				// 之前,每个charts子组件通过memo浅比较,但是使用了ref之后,memo不再生效,所有此处要通过useCallback来缓存回调函数来实现memo的效果
     // charts子组件: 
     const child = React.forwardRef((props,ref) =>{
     		<Box {...config} chartRef={ref} />
     })
     

  4. a通过react-redux获得b组件点击指令后,开始按照3步骤收集dom到ref的current中,存在storage中,由于生成base64的过程是异步的,所以在PageB中无法获取实时的storage. 所以需要在PageB中通过状态锁让页面在跳转的过程中只刷新一次

     兄弟组件b点击时同时生成一个同步的sessionStorage的标记作为在PageB中执行状态锁的依据
     

  5. 生成pdf的代码: html2canvas 和 jspdf
     1.

  import html2canvas from 'html2canvas'
  import {jsPDF} from 'jspdf'
  
  const printDocument = async () => {
          await html2canvas(pdfRef.current, {
              allowTaint: true,
              scrollY: 0,
              scrollX: 0,
              useCORS: true,
              width: 1040,
              height: pdfRef.current.offsetHeight,
          }).then(function (canvas) {
              var contentWidth = 900
              var contentHeight = 5060
              var pageHeight = (contentWidth / 592.28) * 841.89
              var leftHeight = contentHeight
              var position = 0
              var imgWidth = 595.28
              var imgHeight = 3400
              var pageData = canvas.toDataURL('image/jpeg', 1.0)
              var pdf = new jsPDF('', 'pt', 'a4')
              if (leftHeight < pageHeight) {
                  pdf.addImage(pageData, 'JPEG', 0, 0, imgWidth, imgHeight)
              } else {
                  while (leftHeight > 0) {
                      pdf.addImage(pageData, 'JPEG', 0, position, imgWidth, imgHeight)
                      leftHeight -= pageHeight
                      position -= 841.89
                      if (leftHeight > 0) {
                          pdf.addPage()
                      }
                  }
              }
              window.open(pdf.output('bloburl', {filename: 'new_file.pdf'}), '_blank')
          })
      }
  
  

  2. 
  

  import html2canvas from 'html2canvas'
  import {jsPDF} from 'jspdf'
  
  const printDocument = async () => {
           await html2canvas(pdfRef.current, {scrollY: -window.scrollY, scale: 1}).then((canvas) => {
               const contentDataURL = canvas.toDataURL('image/png', 1.0)
               let pdf = new jsPDF('l', 'mm', 'a4')
               let imgWidth = 300
               let pageHeight = pdf.internal.pageSize.height
               let imgHeight = (canvas.height * imgWidth) / canvas.width
               let heightLeft = imgHeight
               let position = 0
  
               pdf.addImage(contentDataURL, 'PNG', 0, position, imgWidth, imgHeight)
               heightLeft -= pageHeight
  
               while (heightLeft >= 0) {
                   position = heightLeft - imgHeight
                   pdf.addPage()
                   pdf.addImage(contentDataURL, 'PNG', 0, position, imgWidth, imgHeight)
                   heightLeft -= pageHeight
               }
            //直接保存   // pdf.save('download.pdf') 
            //在线预览  // window.open(pdf.output('bloburl', {filename: 'new_file.pdf'}), '_blank')
           })
  
      }