Design and development practice of UniApp to implement file upload and download functions

UniApp is a cross-platform application development framework that can quickly build multi-terminal applications. In actual project development, file upload and download functions are very common requirements. This article will focus on the design and development practices of how to use UniApp to implement file upload and download functions, with code examples attached.

Design and development practice of file upload function:

First, you need to create a file selector in the page to select the file to be uploaded.

<template>
  <div>
    <input type="file" @change="chooseFile">
    <button @click="uploadFile">上传文件</button>
  </div>
</template>

<script>
export default {
  data() {
    return {
      selectedFile: null
    }
  },
  methods: {
    chooseFile(e) {
      this.selectedFile = e.target.files[0]
    },
    uploadFile() {
      // 创建FormData对象，用于封装要上传的文件
      let formData = new FormData()
      formData.append('file', this.selectedFile)
      
      // 发送POST请求，将文件上传至服务器
      uni.request({
        url: 'http://example.com/upload',
        method: 'POST',
        header: {
          'Content-Type': 'multipart/form-data'
        },
        data: formData,
        success(res) {
          console.log(res)
        },
        fail(error) {
          console.log(error)
        }
      })
    }
  }
}
</script>

In the above code, first select the file to be uploaded through the file selector and save it in the selectedFile attribute. Then, the file is encapsulated through the FormData object and used to send the POST request. The requested URL, request method, request header, etc. need to be configured according to the actual situation. Finally, send the request via uni.request and handle success and failure callbacks.

Design and development practice of file download function:

Similar to file upload, file download function also needs to be triggered by providing a download button on the page.

<template>
  <div>
    <button @click="downloadFile">下载文件</button>
  </div>
</template>

<script>
export default {
  methods: {
    downloadFile() {
      // 发送GET请求，下载文件
      uni.downloadFile({
        url: 'http://example.com/download',
        success(res) {
          // 下载成功后，可以通过res.tempFilePath获取文件的临时路径
          console.log(res)
        },
        fail(error) {
          console.log(error)
        }
      })
    }
  }
}
</script>

In the above code, a GET request is sent through the uni.downloadFile method to download the file locally. The requested URL needs to be configured according to the actual situation. After the download is successful, you can obtain the temporary path of the file through res.tempFilePath in the callback function. You can use this path to display or perform other operations.

In actual project development, the file upload and download functions often cooperate with the server-side API interface, and the interface needs to be called and configured accordingly. In addition, you need to note that when uploading files, you need to set the request header Content-Type to multipart/form-data, and use FormData for file encapsulation.

Summary:

This article introduces the design and development practice of UniApp to implement file upload and download functions through sample code. Through learning and practice, we can better understand and master the implementation principles and methods of file uploading and downloading in UniApp, so that we can apply it efficiently in actual projects.

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