onActivityResult Uri - create subfolder and get DocumentUri of new subfolder

I take the result of my file chooer in onActivityResult an build a DocumentUriUsingTree. Now I take this DocumentUri, build a DocumentFile to create a new folder.

onActivityResult:

if (resultCode  == RESULT_OK) {
                    
                    uri = data.getData();

                    int takeFlags = data.getFlags();
                    takeFlags &= (Intent.FLAG_GRANT_READ_URI_PERMISSION |
                            Intent.FLAG_GRANT_WRITE_URI_PERMISSION );

                    if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.O_MR1) {
                        getContext().getContentResolver().takePersistableUriPermission(uri,
                                Intent.FLAG_GRANT_READ_URI_PERMISSION |
                                        Intent.FLAG_GRANT_WRITE_URI_PERMISSION
                        );
                    }

                    DocumentFile subfolderDf = DocumentFile.fromTreeUri(this,uri);
                    subfolderDf.createDirectory("TestFolder");

                    uriDirFolder = uri.toString();
                    editor = getSharedPreferences(PREFS_NAME, MODE_PRIVATE).edit();
                    editor.putString(PREF_FILE_OBSERVER, uriDirFolder);
                    editor.apply();
}

resultUri == uriDirFolder get from SharedPreference get-Methode

Uri docUriTree = DocumentsContract.buildDocumentUriUsingTree(Uri.parse(resultUri), DocumentsContract.getTreeDocumentId(Uri.parse(resultUri)));

docTreeUri = content://com.android.externalstorage.documents/tree/3339-6133%3AStorage%20Card%2FMusic%....

DocumentFile df = DocumentFile.fromTreeUri(this, docUriTree);
DocumentFile dirDf = df.createDirectory(dirName);

dirDf looks like content://com.android.externalstorage.documents/tree/3339-6133%3AStorage%....dirName

df = DocumentFile.fromTreeUri(this,dirDf.getUri());

df returns the parent folder and not the new created folder

I need the DocumentFileUri from the new folder to use an OutputStreamon it for saving files into it.

What I'm doing wrong here?

Thanks, Alejandro

DocumentFile subfolderDf = DocumentFile.fromTreeUri(this,uri); subfolderDf.createDirectory("TestFolder");

Change to:

            DocumentFile folder = DocumentFile.fromTreeUri(this, uri);
            DocumentFile subfolder = folder.createDirectory("TestFolder");

            if ( subfolder == null )
            {
                Toast.makeText(context, "Sorry, could not create a subfolder with name TestFolder", Toast.LENGTH_LONG).show();

                return;
            }

            Toast.makeText(context, "Created a subfolder with name TestFolder: " + subfolder.getUri().toString(), Toast.LENGTH_LONG).show();