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Android webview - how to fetch a file from external storage

I have a mobile app that wraps around the web-app, using webview.
The web-app has a button to open a large .zip file (e.g. 100 MB).
The user clicks a button, and selects a .zip file.
This triggers an onChange function with a variable of type File (Blob), which includes attributes like:
file name
file size
file type (application/zip)
The javascript code then parses the .zip file, extracts specific data within it and uses it within the web-app.
This works well within the web-app, when the app is called via the Chrome browser.
For example when operated in chrome browser on an Android phone, I can pull the .zip file and open it in the web-app.
I want to do the same but using the mobile app.
I am able to pick up the .zip file using a File Chooser, and pass it to Webview but I have problems to fetch the file from the Javascript code.
For reference, I am able to pass an image, by creating a data_uri using stringBuilder and passing the content (as data:image/jpeg;base64).
But the zip file is much larger.
When calling fetch(fileUri) from the Javascript side I'm getting errors.
I'm using the following uri
/storage/emulated/0/Android/data/com.example/files/Download/file2.zip
The fetch succeeds but returns a blob with size of 165 (i.e. not the actual size of the file) which hosts the error message:
{
"error": "Not Found",
"message": "The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again."
}
The program flow is like so:
I select a .zip file via FileChooser.
In onActivityResult, the uri value is /document/msf:12858 (seen via uri = intent.getData();)
The uri needs to be mapped into a real path file url, such that the fileUrl will be passed to webview.
Webview will then fetch the file using the fileUrl.
I searched how to get the real path file url when selecting a file with FileChooser, and found
this, and this links.
I wasn't able to get the real file path, so I decided to read the file and write it to another location, so I can get a file path. (this is not efficient and done just to check the functionality).
I create the new file using the following code:
InputStream stream = context.getContentResolver().openInputStream(uri);
File file2 = new File(context.getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS), "file2.zip");
writeBytesToFile(stream, file2);
I don't see any errors when creating the file, and when creating the file, the number of bytes that are read and written to the new file are as expected.
For file2, I get a value of:
/storage/emulated/0/Android/data/com.example/files/Download/file2.zip
Then, within the Javascript code I fetch this file path.
But I'm getting a Blob with the "file-not-found" content as above.
So:
How can I verify that the file is indeed created and that the path can be fetched from webview?
How can I get the real file path of the original selected file, so I don't have to read and write the original file to new location just to get the file path?
Thanks

I was able to get the file from external storage by doing the following steps:
create an initial uri (uri1)
The uri is created by:
creating a temporary file (file1) in the storage dir via
context.getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS)
I'm not sure why a temporary file need to be created but if I don't create a file I cannot get the uri.
createFile3
get the uri via
Uri uri1 = FileProvider.getUriForFile(context, "com.example.android.fileprovider", file1);
create an intent with the following attributes:
Intent.ACTION_OPEN_DOCUMENT
category: Intent.CATEGORY_OPENABLE
type: "application/zip"
extra attribute: fileIntent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, uri1);
this opens a dialog box for selecting openable zip files in the Downloads directory,
after the file is selected, a new uri (uri2) is created that includes the name of the selected file.
extract the name of the file via
String fileName = getFileName(context, uri2);
create the dirPath by appending the filename
dirPath = "/data/user/0/com.example/" + fileName;
if the dirPath does not exist (first time), write the file to its dirPath location.
on successive ocassions dirPath exists, so there is no need to re-write the file.
open the file with regular Java means, e.g. via
ZipFile zip = new ZipFile(dirPath);

Partial download of mp4 file with rn-fetch-blob, react-native-video throwing unrecognized error

I'm trying to implement local video caching into my video-streaming application.
I'm using:
react-native-video for video playback
rn-fetch-blob for downloading files
I've managed to start the download at the beginning, replace the original URL with the local one and continue with the playback from my local file (it works as expected) - even with partial file (as long as I start from 0).
The main problem is seek function. If a user wants to start watching at e.g. 120s - download will still start at 0B. I've implemented Range header in the Fetch API looking something like this:
"Range": "bytes: {oneSecondInBytes * whereYouWantToStartWatchingInSeconds}-{fileSizeInBytes}"
to overcome this problem. Now download starts at desired Bytes and downloads only desired part of the video file.
The download works normally but video playback throws Unrecognized media format error. Also tried adding some bytes for headers at the beginning (0-10000B) - to try and recognize the video file, no luck.
So I'm wondering if it's possible to implement partial video file download with rn-fetch-blob and be able to play the file back using react-native-video (not starting at the beginning of the file), later also add other pieces to the file (until the whole download is complete). How could I convince react-native-video that my partial download is indeed proper mp4 file?
UPDATE
I've messed around with HTTP GET headers for a while and actually got somewhere. Not a complete solution but might help someone:
"Content-Type": "video/mp4",
"Range": `bytes=0-1000, 45111150-`,
"Accept-Ranges": "bytes",
"Content-Length": "89024062"
^^ these are my test headers. Had to add two value to Range. The first one just downloads the first part of the file to get headers and to recognize the file type. The second one is from the "seek point" owards. Video now plays and file type is recognized.

Questions about extract.autodesk.io - taking a file path instead of choosing with the file chooser

I'm trying to modify the project so I could plug in a file path or a file as a variable instead of the user choosing the model file. So I'm looking for where the actual upload happens.
In submitProject():
https://github.com/cyrillef/extract.autodesk.io/blob/master/www/js/app.js#L129
I see that it just sends (with an ajax request) an object that holds the file name and unique identifier but not the actual binary file.
In here:
https://github.com/cyrillef/extract.autodesk.io/blob/master/www/js/upload-flow.js#L34
there's r.upload(), is this the actual upload of the model?
Does it start to upload the file right as you press ok in the file chooser?
Is there a way to give it a file path to upload instead of uploading with the form and file chooser?

The author of this sample should be on Christmas vacation, I just downloaded and setup the extractor sample on my machine, with a little debug into the code, let me try to answer as much as I can.
In general, I think some of your understanding is correct, but let me explain a little more:
For a local file to be uploaded and translated, there are actually 2 steps of actual “upload”.
As you mentioned, when you press ok in the file chooser, yes, the file will be first uploaded to the "extractor" server as you noticed by some methods like r.upload(), it’s actually using a JavaScript library call “flow.js", which provides multiple simultaneous, stable, fault-tolerant and resumable/restartable file uploads via the HTML5 File API. I am not expert on this, but you can check that module about how to use it to upload a file.
By now, your file is uploaded from client to the "extractor" server, but if you want to translate the file to "svf", the file is required to be uploaded to Autodesk Server(OSS), that is done by clicking “submit my project” buton, when you click this button, as you mentioned, from client, it will call the method submitProject() in https://github.com/cyrillef/extract.autodesk.io/blob/master/www/js/app.js, this method will send a post request of “/api/projects” to the "extractor" server, if you check the code at server side https://github.com/cyrillef/extract.autodesk.io/blob/master/server/projects.js , you can see the extractor server actually upload the file to Autodesk OSS, and then triggers the translation service.

This feature (passing a URL string vs a file binary) is already implemented. You can use the uri: edit box and paste your file URL there. It supports http(s) or S3 uri with access token.
The physical upload happens in this file, whereas the SubmitProject() code sends only information as JSON. The JSON object only contains a reference to the file which was uploaded using flow.js. But would contain the uri string if you had choose that method.

Downloading a file to the file system in WinJS

We are developing an app that is to download files from HTTP URLs, the extensions/file types of which we will not know until runtime. We've been following this tutorial as a starting point, but since we aren't dealing with images, it hasn't helped us.
The issue is that the code in the tutorial will get you a Blob object and I can't find any code that will allow us to either:
Convert the Blob to a byte array.
Save the Blob straight to the file system.
The ultimate goal is to seamlessly save the file at the given URL to the file system and launch it with the default application, or to just launch it from the URL directly (without the save prompt you get if you just call Windows.System.Launcher.launchUriAsync(uri);).
Any insight anyone might have is greatly appreciated.

Regarding downloading content into byte array:
Using WinJS.xhr with the responseType option as 'arraybuffer' will return the contents in ArrayBuffer. A javascript typed array can be instantiated from the ArrayBuffer for example UInt8Array. This way contents can be read into byte array. code should look something like this:
// todo add other options reqd
var options = { url: url, responseType: 'arraybuffer' };
WinJS.xhr(options).then(function onxhr(ab)
{
var bytes = new Uint8Array(ab, 0, ab.byteLength);
}, function onerror()
{
// handle error
});
Once you take care of permissions to save the file to file system either by user explicitly picking the save file location using SaveFilePicker or pick folder using folder picker - file can be saved on local file system. Also, file can be saved to app data folder.
AFAIK, html/js/css files from local file system or the app data cannot be loaded for security reasons. Although DOM can be manipulated under constraints, to add content. I am not sure of your application requirements. You might need to consider alternatives instead of launching downloaded html files.

Fetch geotag from uploaded images with Google Apps Script?

The idea: at the moment I have a script which watch for new images uploaded (from smartphone or tab) to a specific folder. The script moves image to some subfolder depending on image's name and append a row with corresponding data to specific spreadsheet.
Is it possible to fetch geo information from uploaded to Google Drive images (using smartphone) to put them to the spreadsheet? Searched over the API, but look there is no native function for that. Any 3rd-party solutions?

It is possible to accomplish your task (to get geo-data of uploaded images) using GAS. There is no GAS service performing it and I am almost sure now there is no a 3rd-party solution for your task. A brief scheme for the task is the following
to traverse all files in the image folder.
to open every file by using the DocsList.getFileById method
to check if the file data has required MIME-type. I assume, that JPEG files are most wanted to you. They have the image/jpeg MIME-type. The getContentType method of the BLOB class returns the data type.
for filtered files, to get the data by using the BLOB.getBytes method, find in the data the EXIF-matadata (see bellow), parse it and get the geotags. The geo-info stored as metada inside of image file and usually has EXIF format. There is a number of Javascript libraries which are able to read EXIF of JPEG files, for instance, this one. You can either write your own code which will perform this step or modify the exist library (if the library license permits it). The exist library modification should not be a problem.
to publish the retrieved geo-information to a spreadsheet.