Develop Reference

How can I rename a folder I created in the shared storage?

My app creates folders in the shared storage (DCIM/ and Pictures/ directories), which I want to be able to rename afterwards.
I save the images using MediaStore, the folders are created automatically.
Android Q (and above) already takes care of creating the folders if
they don’t exist. The example is hard-coded to output into the
DCIM folder. If you need a sub-folder then append the sub-folder name as next:
final String relativeLocation = Environment.DIRECTORY_DCIM + File.separator + “YourSubforderName”;
https://stackoverflow.com/a/56990305/10226383
I just can't seem to figure out how to do it, is that even possible with scoped storage, do I need to use MediaStore or SAF?
I know before the change to scoped storage you could do it this way:
File oldfolder = new File("path of the old folder","old name");
File newfolder = new File("path of the new folder","new name");
oldfolder.renameTo(newfolder);
If someone could point me in the right direction I would be really grateful!

How could I create a file in the "Internal Storage" Directory?

I have a Samsung Galaxy S6. I'm currently working on a test application where I would like quick access to a folder with my files.
Using the provided "My Files" Application, it specifies that all those folders are in the "Internal Storage" folder.
I know that internal storage is private, but I want to create a folder in the default folder that windows accesses when the phone is plugged in.
For example, the following code does not create the directory in the correct location.
File storage = new File("/testappplication");
if(!storage.exists()) {
storage.mkdir();
System.out.println("Folder Created");
}
I just want to know the path where to create the folder. Many other applications have storage here, so I know its possible.

You can't create a directory inside the internal storage of the device. Except you've a root access for the app.
So, the following code won't work:
File storage = new File("/testappplication");
Because it tell the app to create a testappplication in the root folder.
You can only create the directory inside your app private folder within the following path:
String path = getFilesDir().getAbsolutePath();
And make the folder using the path.
Or you can use something like this:
File folder = new File(context.getFilesDir(), "testappplication");
if (!folder.exists()) {
folder.mkdirs();
} else {
// folder is exist.
}
Read more at Saving Files

First just for trial make runtime permmision and then try the following code
private void createInternalFile() {
File mediaStorageDir = new File(Environment.getExternalStorageDirectory()+"/"+getApplicationContext()
.getPackageName()+"/File/profile");
if (!mediaStorageDir.exists()) {
mediaStorageDir.mkdirs();
} }
then check your internal storage in which you will find a folder whose name is your package name

After a while later I found the answer to this question.
public void createDirectory() {
File file = new File(Environment.getExternalStorageDirectory(), "/test");
if (!file.exists()) {
file.mkdirs();
Log.w("DEBUG", "Created default directory.");
}
}
This is how you create it code wise. The reason it wasn't creating was due to Samsungs weird permissions.
Make sure you have the storage permission enabled in Settings -> Apps -> App Name -> Permissions. I needed to turn it on so it would create the folder.

Where should I choose to save text file in android?

I hope to export my data as a text file and save it to disk in Android, so I need to choose which folder I will save the file to.
I hope that a normal user can find the folder easily and the app does not need special permission to create the folder.
I have read some document, it seems that there are 3 ways: Context.getFilesDir().getAbsolutePath(), Environment.getExternalStorageDirectory().getAbsolutePath() and Context.getExternalFilesDir(null).
You know some android users don't install SD card, so it seems that Environment.getExternalStorageDirectory().getAbsolutePath() and Context.getExternalFilesDir(null) are be excluded.
Am I only to choose Context.getFilesDir().getAbsolutePath()? or is there a better way? Thanks!
BTW, From the document Android - Where to save text files to?
Save it in internal phone storage, here no users and applications can access these files(unless if phone is rooted). But these files will be deleted one's the user selectes clear data from Settings -> Apps -> .
It seems that normal users can't access the saved text files if I use Context.getFilesDir().getAbsolutePath(), is it right?

Use this if you want a path that the user can modify and can have access
getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS).getAbsolutePath();
More documentation here.
EDIT:
This is how use in case error in some devices:
File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS);
String fname = "TEXT.txt";
File file = new File(path, fname);
if (!path.exists()) {
//noinspection ResultOfMethodCallIgnored
path.mkdir();
}
// YOUR CODE FOR COPY OR CREATE THE FILE TXT in PATH WITH THE VARIABLE file ABOVE

android data save directories

My application is mostly c++ (using NDK) so I use fopen, fwrite, etc. standard functions to create and game save files and write into them.
When I use fopen("game.sav", "wb"), it appears that it's being created at path
/data/user/10/com.my.game/files/game.sav.
My app is multi-user. So I want to have a separated folders where users store their save-files. And instead of the path above I'd like to have paths like
/data/user/10/com.my.game/files/user0/game.sav,
/data/user/10/com.my.game/files/user1/game.sav, etc
My app's frontend is in Java, and when new user is being registered, I want to create a folder /data/user/10/com.my.game/files/user0/. But I don't know how to do it, because
final File newDir = context.getDir("user0", Context.MODE_PRIVATE);
results in path being created at /data/user/10/com.my.game/app_user0 that's a different path.
It is possible to create folders at /data/user/10/com.my.game/files/ and how ?

Simple way to do it, this code you can change it suit many conditions. If you know that your path is different from what getFilesDir() gets you then you can create a File first of all by using a path that you know and the last 2 lines of code will still be same.
File file = this.getFilesDir(); // this will get you internal directory path
Log.d("BLA BLA", file.getAbsolutePath());
File newfile = new File(file.getAbsolutePath() + "/foo"); // foo is the directory 2 create
newfile.mkdir();
And if you know the path to "files" directory:
File newfile2 = new File("/data/data/com.example.stackoverflow/files" + "/foo2");
newfile2.mkdir();
Both code works.
Proof of Working:

Make directories in files internal storage

How do i make directories in internal storage?
I tried this:
File file = getFilesDir();
this makes me goes to folder "/data/data/com.mypackages/files/"
Then i want to make a folder again in that directories, let's say i want to make "myfiles" folder in there so it becomes, "/data/data/com.mypackages/files/myfiles/".
Can anyone tell me how?
I also tried this:
File file = getDir("myfiles", MODE_PRIVATE);
It makes the folder, but it was created with "app_", so the directories becomes "/data/data/com.mypackages/app_myfiles". I don't want that because i can't read the folder if it has "app_" in there.

The solution is under your eyes :D
m_applicationDir = new File(this.getFilesDir() + "");
m_picturesDir = new File(m_applicationDir + "/pictures");
With this code, i save in m_applicationDir the dir of the package (in your case the dir saved in file).
Then simply create a sub-directory named pictures.
So m_picturesDir points to:
/data/data/com.mypackages/files/pictures