How can I create a new folder in the internal memory to save my file?

[Anke]

To create the folder without an extension on all Android versions (in the ASD):

See also here:

Save a text file or an image (Canvas) in the ASD & share it on all Android versions

How to save a file (text, Canvas: image) read and share it on all Android versions. [grafik] Note: You cannot share a text file from the → Private dir (internal storage): /data/user/0/<packageName>/files/