Writing files to publicly accessible documents folder in Android Q - Scoped Storage

Question

Background

After migrating to Android Q I can no longer find a suitable way to gain write access to the documents folder (/storage/emulated/0/Documents)

And before anyone mentions the many other questions on scoped storage I've read through many of them and from what I've seen so far all of the solutions use a app specific directory or accessing a media directory only (not documents folder access).

From what I understand in Android Q I can either choose:

• Use a app specific directory that is only accessible by my app (or apps I give permission to)
• Allow the user to select where they want the file stored (I think this can be a public location) ACTION_OPEN_DOCUMENT_TREE

Problem

The applications I develop are used to conduct tests on subjects, the data from the tests automatically gets stored in the publicly accessible Documents folder somewhat like: /storage/emulated/0/Documents/myAppName/subjectName/testData-todaysDate.pdf

When the user wants to access the test data they plug their smartphone into a computer and navigate to the documents folder and the rest is pretty obvious. For this reason I have to use publicly accessible storage. Also imagine they want to open the test data on their phone via another app, Same deal!

The solution I'm looking for

So the solution I'm looking for needs to be able to do the following:

• Doesn't ask for permission multiple times (once is ok)
• Automatically saves test data without user prompt (as hundreds of tests will be conducted)
• Saves to public documents folder e.g. /storage/emulated/0/Documents/
• Doesn't involve the user selecting the directory so NOT ACTION_OPEN_DOCUMENT_TREE
• Ideally the data is persistent so uninstalling the app doesn't cause data lose

I get that these changes in Android Q are to bring users more "into the loop" with how apps are accessing their data but once they understand how your app is using your data there shouldn't be a problem.

Melindamelinde

AFAIK, there is no solution meeting your requirements. If you switch from Documents/ to Downloads/, you can use MediaStore.Downloads. "but once they understand how your app is using your data there shouldn't be a problem" -- by that argument, you should not have a problem with ACTION_OPEN_DOCUMENT_TREE. The user needs to handle that exactly once, after which you can write as many documents into that tree as you like. – Abednego

With ACTION_OPEN_DOCUMENT_TREE can they select a public location when they setup the app for example and then we reuse that forever? That might be the best solution then, still dangerous as the user can choose a bad location but better then nothing. – Melindamelinde

When the user wants to access the test data they plug their smartphone into a computer and navigate to the documents folder. Is this still possible with an Android Q device? Please report as i have no such device. – Langouste

You can let the MediaStore write your files to /storage/emulated/0/Documents and /storage/emulated/0/Download and /storage/emulated/0/Pictures and /storage/emulated/0/DCIM without any permission needed. – Langouste

"With ACTION_OPEN_DOCUMENT_TREE can they select a public location when they setup the app for example and then we reuse that forever?" -- yes. – Abednego

Check out https://mcmap.net/q/1008707/-how-to-save-pdf-in-scoped-storage – Overglaze

Answer 1

For Android Q only.

String collection = "content://media/1c11-2404/file"; // One can even write to micro SD card
String relative_path = "Documents/MyFolder";

Uri collectionUri = Uri.parse(collection);

ContentValues contentValues = new ContentValues();

contentValues.put(MediaStore.MediaColumns.DISPLAY_NAME, displayName);
contentValues.put(MediaStore.MediaColumns.MIME_TYPE, mimeType);
contentValues.put(MediaStore.MediaColumns.SIZE, filesize);
contentValues.put(MediaStore.MediaColumns.DATE_MODIFIED, modified );
contentValues.put(MediaStore.MediaColumns.RELATIVE_PATH, relative_path);
contentValues.put(MediaStore.MediaColumns.IS_PENDING, 1)

Uri fileUri = context.getContentResolver().insert(collectionUri, contentValues);

Having an uri one can open an output stream to write the content for the file.

Langouste

@blackapps: OK, I can confirm that this works. For external storage, you would use content://media/external/file (also available via MediaStore.Files.getContentUri("external")). For removable storage, you would need the storage ID (1c11-2404 in your code snippet). I am skeptical that this is intended to work, so I would not be shocked if there are problems with this technique in future versions of Android. But, this is an excellent find -- thanks for sharing it! – Abednego

Ok I'm slightly confused, before I was using FileOutputStream like so outputStream = new FileOutputStream(filePath, false); then I would simply outputStream.write(dataToWrite.getBytes()); and then .flush() and .close() This only works with File of course, so I am not sure how you open an outputstream with a uri as you suggest? – Melindamelinde

OutputStream is = getContentResolver().openOutputStream(fileUri);. – Langouste

Ok between @Langouste and @Abednego I was able to piece together enough to get something working. This is absolutely brilliant but as others have said I'm not sure how intended this was.Also worth noting android:requestLegacyExternalStorage="true" will persist (even if removed) unless you clear the data/cache on your app. – Melindamelinde

regarding the UUID of an SD card, I found out it should be lowercase, contrary to what's returned from StorageVolume getUuid() – Dhow

Answer 2

try to put this line in your manifest file for android Q:

    android:requestLegacyExternalStorage="true"

in application tag.

Dight

That is a hack that will not work with versions after Q. – Langouste