Saving Downloaded File Excel to Internal Storage in React Native using Expo

Are you tired of dealing with the nuances of file management in React Native? Do you want to learn how to save downloaded Excel files to internal storage using Expo? Look no further! In this comprehensive guide, we’ll take you through the step-by-step process of downloading an Excel file and saving it to internal storage in your React Native app using Expo.

Why Save Files to Internal Storage?

Before we dive into the tutorial, let’s discuss why saving files to internal storage is important. When you download a file in a React Native app, it’s typically stored in the app’s temporary directory. However, this directory is cleared whenever the app is updated or reinstalled, which means your downloaded files are lost forever! By saving files to internal storage, you can ensure that your users’ data is preserved even after app updates or reinstalls.

Prerequisites

Before we begin, make sure you have the following installed on your development machine:

• Node.js (version 14 or higher)
• npm (version 6 or higher)
• Expo CLI (version 4 or higher)
• A code editor or IDE of your choice

Step 1: Create a New React Native Project using Expo

Open your terminal and run the following command to create a new React Native project using Expo:

npx expo init myapp

Follow the prompts to choose a template and set up your project. Once the installation is complete, navigate to the project directory:

cd myapp

Step 2: Install Required Dependencies

In your project directory, install the required dependencies using the following commands:

npm install expo-file-system expo-document-picker

The expo-file-system library allows you to interact with the file system on the user’s device, while expo-document-picker enables you to access the device’s document picker.

Step 3: Create a Download Function

Create a new JavaScript file called downloadFile.js in your project directory:

touch downloadFile.js

In this file, add the following code:

import { FileSystem } from 'expo-file-system';
import { DocumentPicker } from 'expo-document-picker';

const downloadFile = async (url) => {
  const { uri } = await FileSystem.downloadAsync(url, FileSystem.documentDirectory + 'example.xlsx');
  return uri;
};

export default downloadFile;

This function takes a URL as an argument, downloads the file using FileSystem.downloadAsync(), and returns the URI of the downloaded file.

Step 4: Create a Save Function

Create another JavaScript file called saveFile.js in your project directory:

touch saveFile.js

In this file, add the following code:

import { FileSystem } from 'expo-file-system';

const saveFile = async (uri) => {
  const info = await FileSystem.getInfoAsync(uri);
  if (!info.exists) {
    throw new Error(`File ${uri} does not exist`);
  }
  await FileSystem.moveAsync(uri, FileSystem.documentDirectory + 'example.xlsx');
  console.log('File saved to internal storage!');
};

export default saveFile;

This function takes the URI of the downloaded file as an argument, checks if the file exists, and then moves it to the internal storage using FileSystem.moveAsync().

Step 5: Integrate Download and Save Functions

In your app’s main component file (e.g., App.js), add the following code:

import React, { useState } from 'react';
import { View, Button, Text } from 'react-native';
import downloadFile from './downloadFile';
import saveFile from './saveFile';

const App = () => {
  const [downloads, setDownloads] = useState([]);
  const [saved, setSaved] = useState(false);

  const handleDownload = async () => {
    const url = 'https://example.com/example.xlsx'; // Replace with your Excel file URL
    const uri = await downloadFile(url);
    setDownloads([...downloads, { uri, name: 'example.xlsx' }]);
  };

  const handleSave = async () => {
    if (downloads.length > 0) {
      await saveFile(downloads[0].uri);
      setSaved(true);
    } else {
      console.log('No files to save!');
    }
  };

  return (
    <View>
      <Button title="Download Excel File" onPress={handleDownload} />
      <Button title="Save to Internal Storage" onPress={handleSave} />
      {saved ? (
        <Text>File saved to internal storage!</Text>
      ) : (
        <Text>No file saved yet...</Text>
      )}
    </View>
  );
};

export default App;

This code creates a simple React Native app with two buttons: “Download Excel File” and “Save to Internal Storage”. When the user presses the download button, the app downloads the Excel file using the downloadFile function. When the user presses the save button, the app saves the downloaded file to internal storage using the saveFile function.

Step 6: Run the App

Finally, run the app using the following command:

npx expo start

Open the app in a simulator or physical device, press the “Download Excel File” button, and then press the “Save to Internal Storage” button. If everything is set up correctly, you should see a success message indicating that the file has been saved to internal storage!

Conclusion

In this article, we’ve covered the step-by-step process of saving downloaded Excel files to internal storage in a React Native app using Expo. By following these instructions, you can ensure that your users’ data is preserved even after app updates or reinstalls.

Remember to replace the sample Excel file URL with your own file URL, and adjust the file name and directory paths as needed.

If you encounter any issues or have questions, feel free to ask in the comments below!

File	Description
downloadFile.js	Downloads a file from a URL and returns the URI of the downloaded file
saveFile.js	Saves a file to internal storage using the provided URI
App.js	The main app component that integrates the download and save functions

Happy coding!

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