Develop Reference

How do I open and display a base64 pdf from inside my Cordova App?

I am creating an App for Android using Cordova, and I would like to open and display a file (PDF or image) that is served from the server as Base64-encoded binary data.
Of course I have read the multiple other posts on the subject that already exist on this website, but none of the proposed solutions have worked for me, more details below.
To be more precise, the server sends a JSON-file to the app, which among many other things contains a string consisting of the base64-encoded contents of a PDF file. I want to convert this data back into the represented PDF and display it to the user.
If this were a pure browser page, I would simply package my base64 data into a data-URL, attach this as the href of some anchor, and add a download-attribute. Optionally I could wrap all of my data into a blob and create an object url for that first.
In Cordova, this does not work. Clicking the <a> does nothing. Here is what I have attempted so far:
Using the file plugin, I can write the binary data to a file on the device. This works, and using a terminal I can see that the file was downloaded correctly, but into an app-private directory which I cannot access normally (e.g. through the file explorer).
Accessing the user's "downloads" folder is blocked by the file system
Using window.open with the file path as the first argument and "_system" as the target does nothing. There is no error but also nothing happens. Setting the target to "_blank" instead, I get an error saying ACCESS_DENIED.
Using cordova.InAppBrowser behaves the same was as window.open
With the plugin file-opener2 installed, the app will not compile, because the plugin is looking for an android4 toolchain, and I am building for android 9 and up
The plugin document-viewer (restricting to PDFs for the time being) suffers the same problem and does not compile.
Passing the data-URI to window.open (or cordova.InAppBrowser) directly loads for a very long time and eventually tells me that the desired page could not be loaded.
The PDF file I am using for testing is roughly 17kb after converting to base64. I know this is technically above the spec for how long data-URIs can be, but Chrome in the browser has no trouble with it whatsoever, and using a much shorter URI (only a few dozen bytes) produces the same behavior.
Ideally, what I would like to do, is download the file and then trigger the user's standard browser to open the file itself. That was, I would not have to deal with MIME types and also it would look exactly how the user expected from their own device.
Alternatively, if that doesn't work, I would be ok with downloading the file into a system-wide directory and prompting the user to open it themselves. This is not optimal, but I would be able to swallow that pill.
And lastly, if there is a plugin or some other solution that solves the problem amazingly, but for PDFs only, then I can also work out something else for images (e.g. embedding a new into my app and assigning the URI to that).
I would be thankful for any suggestion you might have on how to solve this problem. The code I use to download the file currently is shown below.
Thank you for your time.
var filePath = cordova.file.externalDataDirectory; // Note: documentsDirectory is set to "" by Cordova, so I cannot use that
var fileName = "someFileName.pdf";
var mime = "application/pdf";
var dataBlob = /* some blob containing the binary data for a PDF */
function writeFile(fileEntry, dataBlob) {
// Create a FileWriter object for our FileEntry.
// This code is taken directly from the cordova-plugin-file documentation
fileEntry.createWriter(function (fileWriter) {
fileWriter.onwriteend = function() {
console.log("Successful file write...");
readFile(fileEntry);
};
fileWriter.onerror = function (e) {
console.log("Failed file write: " + e.toString());
};
fileWriter.write(dataBlob);
});
}
window.resolveLocalFileSystemURL(
filePath,
function onResolveSuccess (dirEntry) {
dirEntry.getFile(
fileName,
{ create: true },
function onGetFileSuccess (file) (
writeFile(file, dataBlob);
// At this point, the file has been downloaded successfully
window.open(file.toURL(), "_system"); // This line does nothing, and I don't understand why.
}
);
}
);

I managed to solve the problem.
As per the documentation of the file-opener2 plugin, you need to also add the androidx-adapter plugin to correct for the outdated (android 4) packages. With the plugins file, file-opener2 and androidx-adapter installed, the complete code is the following:
var filePath = cordova.file.externalDataDirectory; // Note: documentsDirectory is set to "" by Cordova, so I cannot use that
var fileName = "someFileName.pdf";
var mime = "application/pdf";
var dataBlob = /* some blob containing the binary data for a PDF */
function writeFile(fileEntry, dataBlob) {
// Create a FileWriter object for our FileEntry.
// This code is taken directly from the cordova-plugin-file documentation
fileEntry.createWriter(function (fileWriter) {
fileWriter.onwriteend = function() {
console.log("Successful file write...");
readFile(fileEntry);
};
fileWriter.onerror = function (e) {
console.log("Failed file write: " + e.toString());
};
fileWriter.write(dataBlob);
});
}
window.resolveLocalFileSystemURL(
filePath,
function onResolveSuccess (dirEntry) {
dirEntry.getFile(
fileName,
{ create: true },
function onGetFileSuccess (file) (
writeFile(file, dataBlob);
// At this point, the file has been downloaded successfully
cordova.plugins.fileOpener2.open(
    filepath + filename,
    mime,
    {
     error : function(){ },
success : function(){ }
    }
);
}
);
}
);

Write image file to Firebase Storage from HTTP function

I am trying to write an image Firebase Storage via a Cloud Function (for more suitable write access).
My current attempt is to read the file object on the client, send it (the data) to an http firebase function, and then save it to storage from there. After saving the file successfully, I try using the download url as an img src value, but the file does not display. I also see an error in the Storage console (Error loading preview) when attempting to view the file.
If I save the data in Storage as base64, I can copy the contents of the file into the img src attribute, and it displays fine. However, I'd like to simply use the download URL as I could do if I just uploaded the image via the client SDK or directly via the console.
In the client, I'm simply using FileReader to read the uploaded file for sending. I've tried all the ways of reading it (readAsText,readAsBinaryString, readAsDataURL, readAsArrayBuffer), but none seem to solve the issue.
Here is how I am uploading the file via the Firebase Function:
import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';
import * as path from 'path';
import * as os from 'os';
import * as fs from 'fs-extra';
export default functions.https.onCall(async(req, context) => {
const filename = req.filename;
const bucket = admin.storage().bucket(environment.bucket)
const temp_filename = filename;
const temp_filepath = path.join(os.tmpdir(), temp_filename);
await fs.outputFile(temp_filepath, req.data, {});
// Upload.
await bucket.upload(temp_filepath, {destination: 'logos'})
.then((val) => {})
.catch((err) => {});
});
This uploads the file successfully, however, the Download URL does not work when used as the img src attribute.
One thing I have noticed is that when using the client SDK to send a file (via AngularFireStorage), the payload is the raw png contents. E.g. a snippet of the file:
PNG
IHDRÈÈ­X®¤IDATx^í]
Eµ¾·{&1,!dù»*yVQ#PTEDPA>ÊâC\P"ÈÄ"
F}òIW÷üCL#BÉL÷}
....
However, reading the file as text does not yield this encoding. I have tried several other encodings.
Any help would be immensely appreciated.
Edit
Here is what I mean about using the download URL:
<img alt='logo' src='https://firebasestorage.googleapis.com/v0/b/y<project-name>/o/logos%2FAnM65PlBGluoIzdgN9F5%2Fuser.png?alt=media&token=<token>' />
The above src url is the one provided in the Firebase Storage console when clicking on the file. It is labeled as 'Download URL' (I believe this is the one retrieved by calling getDownloadUrl() via the sdk).
When using AngularFireStorage to put the file in storage, the Download URL will work. When I say it 'will work', I mean the image will display properly. When using FileReader to pass the data to an http cloud function to upload (as seen above), the image will not display. In other words, after uploading the file via the backend, the download url does in fact provide what was uploaded, it's just not in a format that an img tag can display.
One possible issue may be that I am not getting the encoding correct when using FileReader readAsText. Here is what I am doing with FileReader:
const reader = new FileReader();
reader.onloadend = () => {
firebase.functions().httpsCallable('http_put_logo')(reader.result);
};
// Have tried various encodings here, as well as all reader methods.
reader.readAsText(file);
Edit 2
All of the discussion on this question so far seems to be around correctly getting the download URL. I'm not sure if Firebase docs have this information, but the download URL is available in the Storage console. I'm simply copying and pasting that URL to for testing purposes at the moment.
The reason why I am doing this is because I plan to save these image URLs in the DB since they are going to be frequently used and publicly readable. So, I'm not going to use the getDownLoadURL() method to fetch these images, I'm simply just going to link to them directly in img tags.
Here is an image of my console to see what I mean (bottom right):
You just have to click it and copy it. You can then open it in a browser tab, download it, use it as a src value, etc.
Edit 3
Here is an image of what the request payload looks like when using the client sdk:
Here is when I read the file as text and send to backend for upload:
Notice there are differences in the payloads. That's why I'm uncertain if I'm properly reading the file or encoding it incorrectly.

What part of your code is taking care of getting the URL? I recently used a similar approach to uploading images to Firebase Storage using cloud functions. What worked best for me was to execute a different function to get the URL after the upload is complete. Something like this:
const bucket = admin.storage().bucket(environment.bucket)
const temp_filename = filename;
const temp_filepath = path.join(os.tmpdir(), temp_filename);
await fs.outputFile(temp_filepath, req.data, {});
// Upload.
await bucket.upload(temp_filepath, {destination: 'images'})
.then((val) => {retrieveUrl(temp_filename)})
.catch((err) => {});
retrieveUrl = (imageName) => {
const storage = firebase.storage();
storage.ref(`/images/${imageName}.jpg`).getDownloadURL()
.then( url => {
/*Save the url to a variable or attach it directly to the src of your image, depending on the structure of your project*/
})
.catch(err => console.log(err));
}
Keep in mind that you need to install firebase in your project in order to call firebase.storage.

Blob name issue with new tab in chrome and firefox [duplicate]

In my Vue app I receive a PDF as a blob, and want to display it using the browser's PDF viewer.
I convert it to a file, and generate an object url:
const blobFile = new File([blob], `my-file-name.pdf`, { type: 'application/pdf' })
this.invoiceUrl = window.URL.createObjectURL(blobFile)
Then I display it by setting that URL as the data attribute of an object element.
<object
:data="invoiceUrl"
type="application/pdf"
width="100%"
style="height: 100vh;">
</object>
The browser then displays the PDF using the PDF viewer. However, in Chrome, the file name that I provide (here, my-file-name.pdf) is not used: I see a hash in the title bar of the PDF viewer, and when I download the file using either 'right click -> Save as...' or the viewer's controls, it saves the file with the blob's hash (cda675a6-10af-42f3-aa68-8795aa8c377d or similar).
The viewer and file name work as I'd hoped in Firefox; it's only Chrome in which the file name is not used.
Is there any way, using native Javascript (including ES6, but no 3rd party dependencies other than Vue), to set the filename for a blob / object element in Chrome?
[edit] If it helps, the response has the following relevant headers:
Content-Type: application/pdf; charset=utf-8
Transfer-Encoding: chunked
Content-Disposition: attachment; filename*=utf-8''Invoice%2016246.pdf;
Content-Description: File Transfer
Content-Encoding: gzip

Chrome's extension seems to rely on the resource name set in the URI, i.e the file.ext in protocol://domain/path/file.ext.
So if your original URI contains that filename, the easiest might be to simply make your <object>'s data to the URI you fetched the pdf from directly, instead of going the Blob's way.
Now, there are cases it can't be done, and for these, there is a convoluted way, which might not work in future versions of Chrome, and probably not in other browsers, requiring to set up a Service Worker.
As we first said, Chrome parses the URI in search of a filename, so what we have to do, is to have an URI, with this filename, pointing to our blob:// URI.
To do so, we can use the Cache API, store our File as Request in there using our URL, and then retrieve that File from the Cache in the ServiceWorker.
Or in code,
From the main page
// register our ServiceWorker
navigator.serviceWorker.register('/sw.js')
.then(...
...
async function displayRenamedPDF(file, filename) {
// we use an hard-coded fake path
// to not interfere with legit requests
const reg_path = "/name-forcer/";
const url = reg_path + filename;
// store our File in the Cache
const store = await caches.open( "name-forcer" );
await store.put( url, new Response( file ) );
const frame = document.createElement( "iframe" );
frame.width = 400
frame.height = 500;
document.body.append( frame );
// makes the request to the File we just cached
frame.src = url;
// not needed anymore
frame.onload = (evt) => store.delete( url );
}
In the ServiceWorker sw.js
self.addEventListener('fetch', (event) => {
event.respondWith( (async () => {
const store = await caches.open("name-forcer");
const req = event.request;
const cached = await store.match( req );
return cached || fetch( req );
})() );
});
Live example (source)
Edit: This actually doesn't work in Chrome...
While it does set correctly the filename in the dialog, they seem to be unable to retrieve the file when saving it to the disk...
They don't seem to perform a Network request (and thus our SW isn't catching anything), and I don't really know where to look now.
Still this may be a good ground for future work on this.
And an other solution, I didn't took the time to check by myself, would be to run your own pdf viewer.
Mozilla has made its js based plugin pdf.js available, so from there we should be able to set the filename (even though once again I didn't dug there yet).
And as final note, Firefox is able to use the name property of a File Object a blobURI points to.
So even though it's not what OP asked for, in FF all it requires is
const file = new File([blob], filename);
const url = URL.createObjectURL(file);
object.data = url;

In Chrome, the filename is derived from the URL, so as long as you are using a blob URL, the short answer is "No, you cannot set the filename of a PDF object displayed in Chrome." You have no control over the UUID assigned to the blob URL and no way to override that as the name of the page using the object element. It is possible that inside the PDF a title is specified, and that will appear in the PDF viewer as the document name, but you still get the hash name when downloading.
This appears to be a security precaution, but I cannot say for sure.
Of course, if you have control over the URL, you can easily set the PDF filename by changing the URL.

I believe Kaiido's answer expresses, briefly, the best solution here:
"if your original URI contains that filename, the easiest might be to simply make your object's data to the URI you fetched the pdf from directly"
Especially for those coming from this similar question, it would have helped me to have more description of a specific implementation (working for pdfs) that allows the best user experience, especially when serving files that are generated on the fly.
The trick here is using a two-step process that perfectly mimics a normal link or button click. The client must (step 1) request the file be generated and stored server-side long enough for the client to (step 2) request the file itself. This requires you have some mechanism supporting unique identification of the file on disk or in a cache.
Without this process, the user will just see a blank tab while file-generation is in-progress and if it fails, then they'll just get the browser's ERR_TIMED_OUT page. Even if it succeeds, they'll have a hash in the title bar of the PDF viewer tab, and the save dialog will have the same hash as the suggested filename.
Here's the play-by-play to do better:
You can use an anchor tag or a button for the "download" or "view in browser" elements
Step 1 of 2 on the client: that element's click event can make a request for the file to be generated only (not transmitted).
Step 1 of 2 on the server: generate the file and hold on to it. Return only the filename to the client.
Step 2 of 2 on the client:
If viewing the file in the browser, use the filename returned from the generate request to then invoke window.open('view_file/<filename>?fileId=1'). That is the only way to indirectly control the name of the file as shown in the tab title and in any subsequent save dialog.
If downloading, just invoke window.open('download_file?fileId=1').
Step 2 of 2 on the server:
view_file(filename, fileId) handler just needs to serve the file using the fileId and ignore the filename parameter. In .NET, you can use a FileContentResult like File(bytes, contentType);
download_file(fileId) must set the filename via the Content-Disposition header as shown here. In .NET, that's return File(bytes, contentType, desiredFilename);
client-side download example:
download_link_clicked() {
// show spinner
ajaxGet(generate_file_url,
{},
(response) => {
// success!
// the server-side is responsible for setting the name
// of the file when it is being downloaded
window.open('download_file?fileId=1', "_blank");
// hide spinner
},
() => { // failure
// hide spinner
// proglem, notify pattern
},
null
);
client-side view example:
view_link_clicked() {
// show spinner
ajaxGet(generate_file_url,
{},
(response) => {
// success!
let filename = response.filename;
// simplest, reliable method I know of for controlling
// the filename of the PDF when viewed in the browser
window.open('view_file/'+filename+'?fileId=1')
// hide spinner
},
() => { // failure
// hide spinner
// proglem, notify pattern
},
null
);

I'm using the library pdf-lib, you can click here to learn more about the library.
I solved part of this problem by using api Document.setTitle("Some title text you want"),
Browser displayed my title correctly, but when click the download button, file name is still previous UUID. Perhaps there is other api in the library that allows you to modify download file name.

Error 756 Too long request String when using onedrive file picker

i am using the onedrive filepicker for javascript
i developed a website where you can save a file directly
1. using the input element
2. changing the file to dataURI format and saving it to onedrive.
using the input element is working perfectly fine
but when i want to change to dataURI and save i get this error from the browser
Error 756 Too long request String
basically i uploading a .docx file and converting to dataURI and requesting save using the filepicker the dataURI is passed to the url request String which becomes very long
but upon some research based on this question
What is the maximum possible length of a query string?
the limit for chrome is 64k characters but when i counted the length of my request url it was 20,102
here is how the one drive file picker works you pass the parameters to an object and pass the function to onedrive.save function which takes care of everything including the calls and authentication also
var odOptions = {
clientId: "1fd8b6bd-4585-4491-a802-7bc9f0fde5da",
action: "save",
// sourceInputElementId: "",
sourceUri: data,
fileName: "fil.txt",
openInNewWindow: true,
advanced: {},
success: function(files) { console.log('success');},
progress: function(p) { console.log("2"); },
cancel: function() {console.log("3"); },
error: function(e) { console.log(e); }
};
console.log("6");
OneDrive.save(odOptions);
can you help me why this is happening and how to solve this problem ?
my final aim is that in my other application i get the files from a server in the form of dataURIs and i want to save these to one drive
is there any other solution ?
you can test the website here https://bandrevu-akhil.github.io/

How to get full path to user's type="file" using jQuery Fileupload

Im trying to build file preview feature before file being uploaded to the server.
Im stucked with the problem of reading file from the user's computer, not a server
Im usuing jquery Fileupload which fires the file processing on the change function
return $('#new_order_file').fileupload({
change: function(e, data) {
return $.each(data.files, function(index, file) {
read_file(file);
console.log(file)
});
},
});
Log gives File - name, size, type, proto and LastmodifiedDate
Than, this part is tricky for me, I know that I have to use FileReader() but Im not sure how to
function read_file(f){
var reader = new FileReader();
reader.onload = function(e) {
$('#CO-show-model').css('display', 'block');
loaded(f.name, e.target.result);
};
reader.readAsArrayBuffer(f);
}
Next, loaded function is for displaying the file model using three.js
function loaded(file) {
var uploaded_file = file // gives 404
// var uploaded_file = './stl/test-file.stl' // ASCII test
}
The fucntion itself is good, I tested it with an hardcoded path to some test file. But the problem is that it was on a server. Now, script gives an 404 for http://example.com/filename.stl which is true, because I pass file.name there. If I just pass file, it gives 404 for http://example.com/[object%20File]
Edit 1:
I tried suggest ReadAsDataUrl, but seems to be that it's not supported by three.js. Also, the FileReader() seems to be ok

Your file is an object so you have to get the right attribute from it.
Take a look here Filereader Mozilla documentation

It's a security feature. Browsers will not give you the actual local url to the file you are uploading.
See How to get full path of selected file on change of <input type=‘file’> using javascript, jquery-ajax?
Edit: Maybe what you are looking for is this question instead? What is the preferred method for loading STL files in Three.js