How to implement file download function in uniapp

How to implement file download function in uniapp

Uniapp is a cross-platform framework that can easily develop and publish applications to multiple platforms. In some application scenarios, we need to implement file download functions, such as downloading music, pictures and other files. This article will introduce how to implement the file download function in uniapp, with code examples.

1. Use uniapp's network request API

Uniapp provides the network request API uni.request to send network requests. We can use this API to download files.

Code example:

uni.request({
  url: 'http://example.com/fileUrl',  // 文件的下载链接
  success: (res) => {
    // 下载成功后将文件保存到本地
    uni.saveFile({
      tempFilePath: res.tempFilePath,  // 下载的临时文件路径
      success: (res) => {
        console.log('保存成功', res.savedFilePath)
      },
      fail: (err) => {
        console.log('保存失败', err)
      }
    })
  },
  fail: (err) => {
    console.log('下载失败', err)
  }
})

In the above code, we use uni.request to send a GET request to download the file to a temporary folder. Then use uni.saveFile to save the temporary file locally. After successful saving, we can obtain the saved file path through res.savedFilePath.

2. Display download progress

If you need to display the progress of file download, you can use the uni.downloadFile API. This API will return a downloadTask object through which the download progress can be monitored.

Code example:

const downloadTask = uni.downloadFile({
  url: 'http://example.com/fileUrl',  // 文件的下载链接
  success: (res) => {
    // 下载成功后将文件保存到本地
    uni.saveFile({
      tempFilePath: res.tempFilePath,  // 下载的临时文件路径
      success: (res) => {
        console.log('保存成功', res.savedFilePath)
      },
      fail: (err) => {
        console.log('保存失败', err)
      }
    })
  },
  fail: (err) => {
    console.log('下载失败', err)
  }
})

// 监听下载进度
downloadTask.onProgressUpdate((res) => {
  console.log('下载进度', res.progress)
  console.log('已经下载的数据长度', res.totalBytesWritten)
  console.log('预期需要下载的数据总长度', res.totalBytesExpectedToWrite)
})

In the above code, we use uni.downloadFile to send a GET request and monitor the download progress through the downloadTask object. The progress will be returned in real time. We can obtain the download progress through res.progress, and obtain the downloaded data length and expected needs through res.totalBytesWritten and res.totalBytesExpectedToWrite The total length of downloaded data.

It should be noted that uni.downloadFile downloads a temporary file, and you need to use uni.saveFile to save the file locally.

3. File download permission

In uniapp, downloading a file requires obtaining permission to write the file. Permissions can be configured in the manifest.json file:

"permission": {
  "scope.userLocation": {
    "desc": "下载文件"
  }
}

At the same time, uni.getSetting# needs to be called in the onLaunch life cycle of the App.vue file. ## Method to obtain the corresponding permissions of the user:

onLaunch: function() {
  uni.getSetting({
    success: (res) => {
      if (!res.authSetting['scope.writePhotosAlbum']) {
        uni.authorize({
          scope: 'scope.writePhotosAlbum',
          success: () => {
            console.log('用户已授权')
          },
          fail: () => {
            console.log('用户拒绝授权')
          }
        })
      }
    }
  })
}

In the above code, if the user has not authorized permissions, you can call the

uni.authorize method to obtain authorization.

Summary:

Through the network request API provided by the uniapp framework, we can easily implement the file download function. At the same time, you can also monitor the download progress through

uni.downloadFile. It should be noted that downloading files requires permission to write files. I hope the code examples in this article can help you implement the file download function in uniapp.

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