How can I retrieve a file from the file system using React Native, for conversion to base64 and http posting as JSON?

Question

I am using the react native template from this article. The code is all available on Github here.

You can use the app to record audio and save to the file system. I figured out how to retrieve the file URIs, but I'm finding it impossible to get the actual contents of the file itself. All I want to do is retrieve the actual file contents as a binary or ascii or hex string or whatever (it's a .m4a file), so I can convert it to base64 encoding and then post it as JSON to my server. Here's what my code looks like:

/src/screens/RecordAudioScreen/RecordAudioScreenContainer.js

onEndRecording: props => async () => {
  try {
    // here is the URI
    console.log("HERE IS THE URI!!");
    const audio_data = "URI: " + props.recording._uri;

    // Help needed here
    // retrieve file contents from the Android/iOS file system
    // Encode as base64
    audio_data = ... // ???????

    // this works already, posts to the server
    fetch("https://myserver.com/accept_file",
    {
        headers: {
          'Accept': 'application/json',
          'Content-Type': 'application/json'
        },
        method: "POST",
        body: JSON.stringify({user_id: 1, audio_data: audio_data})
    })
    .then(function(res){ console.log(res) })
    .catch(function(res){ console.log(res) });
    console.log("FINISHED POST REQUEST!!!")

    await props.recording.stopAndUnloadAsync();
    await props.setAudioMode({ allowsRecordingIOS: false });

  } catch (error) {
    console.log(error); // eslint-disable-line
  }

  if (props.recording) {
    const fileUrl = props.recording.getURI();
    props.recording.setOnRecordingStatusUpdate(null);
    props.setState({ recording: null, fileUrl });
  }
},

I've already tried a bunch of stuff with no success. Ideally I just get the file contents from the File system, convert to base64 and post it off all in this method just in javascript, but this is seemingly very difficult for what should be a pretty standard thing to do in an app based framework.

Here's some stack overflow questions on React Native Fetch Blob which I couldn't make work Fetch Blob 1 Fetch Blob 2

I've tried using React Native Fs, but I can't get it to load properly, I got super bogged down in stuff I didn't understand after trying to eject the app. I'd prefer a plain React Native solution if possible.

I've also tried some code using FormData but couldn't get that to work either.

Maybe the answer is kind of like this question about retrieving images from firebase? I don't know, this is my first attempt at doing anything in React.

It might also have something to do with the "file://" prefix in the URI that gets generated because there's a lot of questions discussing removing that (only for Android, or only for iOS I'm not too clear).

Converting to base64 will be done with something like this, but I need the actual file contents first:

Very appreciative of any help.

Answer 1

Some time ago I wrote a simple example of a record voice app.

To get the files I used this method:

  import RNFS from 'react-native-fs';

  (...)

  getFiles() {
    RNFS.readDir(AudioUtils.DocumentDirectoryPath)
    .then((result) => {
       this.setState({recordedFiles: result});
       return Promise.all([RNFS.stat(result[0].path), result[0].path]);
    })
    .catch((err) => {
      console.log(err.message, err.code);
    });
  }

It worked just fine.

Here's the full example https://github.com/soutot/react-native-voice-record-app

Let me know if it helped. Otherwise we can try a different approach