Example to explain how UniApp implements local file preview function

UniApp is a cross-platform development framework developed based on Vue.js and the native API of WeChat mini programs. It supports simultaneous release to multiple platforms such as iOS, Android, H5, and mini programs. This article will introduce how to use UniApp to implement the local file preview function.

1. Requirements Analysis

In the actual development process, we often need to preview some local files, such as PDF files, word documents, pictures, etc. In mini programs or H5, we can implement this function through the API or third-party plug-ins provided by the open platform. So how to implement it in UniApp?

2. Implementation plan

The uni-app-plus plug-in provided by UniApp can meet our needs. The uni-app-plus plug-in is an extension plug-in of UniApp, which provides some more advanced APIs and functions such as file system, file preview, voice call, etc. This includes the local file preview API.

The steps are as follows:

1. Add the uni-app-plus plug-in in the manifest.json file of the uni-app project, as follows:

{
  "name": "myApp",
  "version": "1.0.0",
  // 添加uni-app-plus插件
  "plus": {
    "plugins": {
      "io": {
        "version": "1.4.4",
        "provider": "uni.plus.io"
      }
    }
  }
}

2. Reference the plug-in on the page that needs to preview the file, and define the preview function, as follows:

<template>
  <view>
    <button @click="previewFile">预览文件</button>
  </view>
</template>

<script>
import io from '@/js_sdk/uni-app-plus/io/io.js'

export default {
  methods: {
    previewFile() {
      // 获取本地文件路径
      const filePath = 'file:///absolute/path/to/file'
      // 获取文件扩展名
      const fileExt = filePath.substring(filePath.lastIndexOf('.') + 1)
      // 定义支持预览的文件类型数组
      const previewableFileTypes = ['pdf', 'doc', 'docx', 'ppt', 'pptx', 'txt', 'jpg', 'jpeg', 'png', 'gif', 'bmp']
      // 判断文件是否支持预览
      if (previewableFileTypes.indexOf(fileExt.toLowerCase()) === -1) {
        uni.showToast({
          title: '该文件类型不支持预览',
          icon: 'none'
        })
        return
      }
      // 调用插件预览文件
      io.previewFile({
        url: filePath,
        fail: (res) => {
          uni.showToast({
            title: '预览文件失败',
            icon: 'none'
          })
        }
      })
    }
  }
}
</script>

3. Implement the effect

Through the implementation of the above code, we can use UniApp Preview local files in the following formats (only some are listed):

• PDF file
• word document (doc and docx)
• ppt document (ppt and pptx)
• Text file (txt)
• Image file (jpg, jpeg, png, gif, bmp)

IV. Summary

Introduction to this article Learn how to use UniApp to implement local file preview function. We can preview local files by using the uni-app-plus plug-in and calling the API provided by it. I hope this article can be helpful to developers who need to implement local file preview.

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