SpringCloud学习(1)-consul

   "react": "^17.0.2" 

1.react去预览pdf文件，并且这个组件可以在移动端展示，但要注意安装版本

 "react-pdf": "^5.7.2"

直接上代码了，做了一个两页的分页，因为放在移动端有个问题，有个文件全部加载手机就卡死了，但这个分页也没解决问题，换了个文件就是好的，代码能优化的地方比较多，自行优化：

import React, { useState, useEffect, useCallback } from 'react';
import { Page, pdfjs } from "react-pdf";
import { Document } from 'react-pdf/dist/esm/entry.webpack';

pdfjs.GlobalWorkerOptions.workerSrc = `//cdnjs.cloudflare.com/ajax/libs/pdf.js/${pdfjs.version}/pdf.worker.js`;

const PdfViewer = ({ file }: any) => {
    const [page_jsx, set_page_jsx]: [any[], React.Dispatch<React.SetStateAction<any[]>>] = useState<any[]>([]);
    const [totalPages, setTotalPages]: [number, React.Dispatch<React.SetStateAction<number>>] = useState(0);
    const [end_num, set_end_num]: [any, React.Dispatch<React.SetStateAction<any>>] = useState(6);

    const viewMore = useCallback(() => {
            let current_end_num = end_num + 5 <= totalPages ? end_num + 5: totalPages;
            set_end_num(current_end_num);
            const array = [];
            for (let i = current_end_num - 6; i < current_end_num; i++) {
                array.push(i);
            }
            let pageJsx = array?.map((a: any) => <Page scale={.5} key={`page_${a}`} pageNumber={a + 1}/>);
            set_page_jsx((jsx_arr: any[]) => [...jsx_arr, ...pageJsx]);
    }, [end_num, totalPages, set_end_num, set_page_jsx])

    useEffect(() => {
      const array = [];
      if (end_num === 6) {
        for (let i = totalPages < 6 ? 0: end_num - 6; i < (totalPages < 6 ? totalPages: end_num); i++) {
            array.push(i);
        }
        let pageJsx = array?.map((a: any) => <Page scale={.5} key={`page_${a}`} pageNumber={a + 1}/>);
        set_page_jsx((jsx_arr: any[]) => [...jsx_arr, ...pageJsx]);
      }
    }, [end_num, set_page_jsx, totalPages])

  return (
    <div style={{ width: '100%', height: '100vh', overflow: 'auto' }}>
        <Document
            className={"pdf-content"}
            file={file}
            onLoadSuccess={({ numPages }: any) => setTotalPages(numPages)}
        >
            {page_jsx?.map((page: any) => page)}
            {totalPages > end_num && <div style={{height: '40px', lineHeight: '40px', textAlign: 'center'}} onClick={() => viewMore()}>View more</div>}
        </Document>
    </div>
  );
};

export default PdfViewer;

2.   pdfjs-dist

"pdfjs-dist": "^2.5.207"，这个插件的版本尤其要记录下，网上查了好多，只把代码放上去，如果版本不对，引入文件路径是不存在的，那么还是直接放代码吧，如第一种方法自行优化下：

import React, { useCallback, useEffect, useRef, useState } from 'react';
const pdfjsLib = require('pdfjs-dist/es5/build/pdf.js');

pdfjsLib.GlobalWorkerOptions.workerSrc = `//cdnjs.cloudflare.com/ajax/libs/pdf.js/${pdfjsLib.version}/pdf.worker.js`;

const PdfViewer = ({ file }: any) => {
  const [totalPages, setTotalPages]: [number, React.Dispatch<React.SetStateAction<number>>] = useState(0);
  const [end_num, set_end_num]: [any, React.Dispatch<React.SetStateAction<any>>] = useState(6);
  const canvasRefs: any = useRef([]);
  const pageNums: any = useRef([]);

  const renderPage = useCallback(async (pdf: any, endNum: any) => {
    pageNums.current = new Array(endNum)?.fill(0).map((_, i) => i + 1);
    
    // 渲染每一页
    for (let i = totalPages < 6 ? 1: endNum - 5; i <= (totalPages < 6 ? totalPages: endNum); i++) {
      const page = await pdf.getPage(i);
      const viewport = page.getViewport({ scale: 1.5 });

      // 创建canvas元素
      const canvas = document.createElement('canvas');
      const context = canvas.getContext('2d');
      canvas.height = viewport.height;
      canvas.width = viewport.width;

      // 将canvas添加到DOM中
      const canvasContainer: any = document.getElementById('pdf-container');
      canvasContainer.appendChild(canvas);

      // 存储canvas的引用以便后续操作
      canvasRefs.current[i - 1] = canvas;

      // 渲染页面
      const renderContext = {
        canvasContext: context,
        viewport: viewport
      };
      await page.render(renderContext);
    }
  }, [totalPages])

  useEffect(() => {
    async function loadPdf() {
      const loadingTask = pdfjsLib.getDocument(file);
      const pdf: any = await loadingTask.promise;
      // 获取总页数
      const numPages: any = pdf.numPages;
      setTotalPages(numPages);
      renderPage(pdf, end_num);
    }

    if (file && end_num === 6) {
      loadPdf();
    }
  }, [file, end_num, renderPage])

  return (
    <>
      <div id="pdf-container">
        {/* 在这里，canvas元素将被动态添加到这个容器中 */}
      </div>
      {totalPages > end_num && <div onClick={async () => {
        if (end_num < totalPages) {
          let current_end_num = end_num + 5 <= totalPages ? end_num + 5: totalPages;
          set_end_num(current_end_num);
          const loadingTask = pdfjsLib.getDocument(file);
          const pdf: any = await loadingTask.promise;
          renderPage(pdf, current_end_num);
        }
      }} style={{height: '40px', lineHeight: '40px', textAlign: 'center'}}>View more</div>}
    </>
    
  );
};

export default PdfViewer;