What should I do if uniapp cannot browse the web page when previewing pdf?

With the rapid development of mobile Internet, more and more applications are beginning to involve file preview issues. As a common document type, the preview of PDF files has also received more and more attention. Recently, I encountered some PDF file preview problems when using the uniapp framework. Today I want to share my experience to help everyone solve this problem.

When using the uniapp framework, in order to preview and print PDF files, we usually use third-party plug-ins. Among them, the most commonly used plug-in is the pdf.js plug-in. This plug-in is an open source JavaScript library developed by the Mozilla Foundation and can be used to render PDF files on the Web. At the same time, the pdf.js plug-in also provides many convenient API interfaces, which allow us to implement more functions.

However, when using the pdf.js plug-in, we may encounter a problem: PDF files cannot be previewed in the uniapp application. The reason is that when opening a PDF file, you need to jump to a new page, but the uniapp framework is a single-page application by default and cannot browse the web. This makes previewing PDF files a very difficult problem.

In order to solve this problem, we can use "routing page" to implement PDF file preview. Specifically, we need to first define a new routing page in the pages.json file of the uniapp application. The code is as follows:

{
  "pages": [
    {
      "path": "pages/index/index",
      "style": {
        "navigationBarTitleText": "uni-app"
      }
    },
    {
      "path": "pages/pdf/preview",
      "style": {
        "navigationBarTitleText": "PDF预览"
      }
    }
  ]
}

In this code, we define a page named "PDF Preview", and the path of this page is "pages/pdf/preview". At the same time, we also need to implement the preview and printing functions of PDF files in the Vue component of this page.

Specifically, we need to perform the following processing in the JavaScript code of the Vue component:

1. First, define a pdf variable in the data attribute of the component to save the PDF document.
2. In the mounted life cycle function of the Vue component, we need to call the pdf.js plug-in after the page is loaded to open and read the PDF file.
3. Next, we need to use the rendering method provided by the pdf.js plug-in in the mounted function to render the PDF file onto the page.
4. Finally, we add an HTML tag element to the template of the Vue component to display the PDF file. The code is as follows:

<template>
  <div>
    <canvas id="pdfViewer"></canvas>
  </div>
</template>

<script>
  import PDFJS from 'pdfjs-dist'
  import 'pdfjs-dist/web/pdf_viewer.css'
  import 'pdfjs-dist/web/pdf_viewer.js'
  
  export default {
    data() {
      return {
        pdf: null,
      }
    },
    mounted() {
      let _this = this
      PDFJS.workerSrc = 'static/js/pdf.worker.js'
      PDFJS.getDocument('static/pdf/sample.pdf').then(function (pdf) {
        _this.pdf = pdf
        let container = document.getElementById('pdfViewer')
        let viewer = new PDFJS.PDFViewer({ container: container })
        viewer.setDocument(_this.pdf)
      })
    }
  }
</script>

Through these processes, we can implement the preview and print functions of PDF files in the uniapp application. It should be noted that when we implement PDF file preview, we need to use a higher version of the pdf.js plug-in. Many tutorials on the Internet use the old version of the pdf.js plug-in, which cannot be used normally in the uniapp application. Therefore, we need to download the latest version of the pdf.js plugin and reference it in the Vue component. At the same time, when calling the pdf.js plug-in, we also need to register it as a global variable in the Vue component to use it correctly.

In short, using the uniapp framework to preview and print PDF files is a very difficult problem. However, with appropriate processing, we can still achieve this function. I hope what I shared today will be helpful to everyone.

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