Upload a file to your server using react native / expo.

react-native-file-upload.js

/*

   IF YOU WANT TO UPLOAD ONE FILE, USE THE CODE BELOW. 
   SEE THE BOTTOM OF THE GIST TO SEE HOW TO UPLOAD MULTIPLE FILES.
        
   HERE'S AN EXAMPLE SOMEONE MADE USING CLOUDINARY: https://gist.github.com/jamielob/5c1a5dc84e50e4507b71299d993dffec

*/


// 1. initialize request
const xhr = new XMLHttpRequest();
// 2. open request
xhr.open('POST', uploadUrl);
// 3. set up callback for request
xhr.onload = () => {
	const response = JSON.parse(xhr.response);

	console.log(response);
	// ... do something with the successful response
};
// 4. catch for request error
xhr.onerror = e => {
	console.log(e, 'upload failed');
};
// 4. catch for request timeout
xhr.ontimeout = e => {
	console.log(e, 'upload timeout');
};
// 4. create formData to upload
const formData = new FormData();

formData.append('file', {
	uri: 'some-file-path', 			// this is the path to your file. see Expo ImagePicker or React Native ImagePicker
	type: `${type}/${fileEnding}`,  // example: image/jpg
	name: `upload.${fileEnding}`    // example: upload.jpg
});
// 6. upload the request
xhr.send(formData);
// 7. track upload progress
if (xhr.upload) {
	// track the upload progress
	xhr.upload.onprogress = ({ total, loaded }) => {
		const uploadProgress = (loaded / total);
		console.log(uploadProgress);
	};
}


// REPLACE #4 WITH THE CODE BELOW IF YOU'RE UPLOADING AN ARRAY OF MULTIPLE FILES
// 4. create formData to upload
const arrayOfFilesToUpload = [
	// ...
];
const formData = new FormData();

arrayOfFilesToUpload.forEach(file => {
	formData.append('file', {
		uri: file.uri, 					// this is the path to your file. see Expo ImagePicker or React Native ImagePicker
		type: `${type}/${fileEnding}`,  // example: image/jpg
		name: `upload.${fileEnding}`    // example: upload.jpg
	});
})

Hello again, I've figured this out. Just in case this helps someone else:

The issue was occurring when running a development bundle on a metro server - axios/xhr was reporting on the status of the upload of the file to the metro proxy rather than to it's final destination on the net.

When I created an apk build everything worked correctly.