How to save file to Uri path in Android

Question

I have a Uri path that the user has granted through ACTION_OPEN_DOCUMENT_TREE.

I save this Uri as string representation to SharedPreferences. Now I want to copy an internal file to a sub folder of that folder and give it the same file name as the internal file.

I use this to get a DocumentFile to the uriTree:

Uri folder = Uri.parse(<getmysaveduristring>);
DocumentFile file = DocumentFile.fromTreeUri(c, folder);

How do I edit the DocumentFile to include a subfolder and a file name?

Uris and DocumentFiles are confusing me a lot at the moment.

Answer 1

Got it like this:

DocumentFile subDirFile = file.createDirectory(subDir);
DocumentFile actualFile = subDirFile.createFile("*/*", dst.getName());

Then use

OutputStream out = c.getContentResolver().openOutputStream(actualFile.getUri());

to open the file.

Took me a while to figure out that using DocumentFiles was essential.