Develop Reference

Hiding a folder in android not using "." extension

How can I hide a folder in android? I am downloading some data from the app which must be accessible only through my application. Currently, I am hiding folders by putting "." extension to the folder name and saving it in the app directory. But it will get visible when switching on "show hidden option" in file managers and enter the particular app data. Kindly suggest some methods by which we can hide data similar to what we see in amazon prime application and all.

Unless the user roots their device all internal files are accessible only to your app. Beyond that, there is no use case and no acceptable reason to hide files from the person who actually owns the device.

Hiding a folder in android not using “.” extension
you can use internal storage as an alternative to hide the folder, if the device is rooted don't allow the app to be installed, if the user roots the device after app install no matter what you do things will be accessible.
//Create internal dir;
File mydir = context.getDir("DIR_NAME", Context.MODE_PRIVATE);

Currently solved my issue by saving files to Internal Storage.
We can use either
File file = new File(context.getFilesDir(), filename);
or
File mydir = context.getDir("DIR_NAME", Context.MODE_PRIVATE);
for saving it in internal directory.
But if rooted device the issue will persist

Android folder to store media files and access them via an absolute path

I'm working on an Android application that needs to store media (document files like pdf or so for later reading) but the main requirement is that all media files have to be accesible through an absolute path (a physical path on filesystem).
I'd like to avoid copying files to external storage (like sdcard or phone internal memory) so to prevent that if application is uninstalled those files remain in phone (and of course to avoid duplicating the size in kb for each file) and instead to keep files in iny App internal resources folder, but tried "file:///asset_folder" whith no success. As far as I know "file:///asset_folder" only Works for a webview to Access www folder but not for regular files.
I'm not sure if there is any app internal data folder which I can access through an absolute path or if not which is the best way to store App resource files.
Thanks in advance!!
Edit: To make it more clear, the resource files are already bundled with the App, and not written during runtime, and what I'd like to know is where to put them so I can later Access them via absolute path for Reading.

To retrive your app specific data
openFileInput(file_name)
To save your app specific data
openFileOutput(file_name, Activity.MODE_PRIVATE)
Update : Read from asset folder. (InputStream)
getAssets().open(fileName);
getAssets().open(fileName, accessMode);
check the image to where to put asset files
now to make other app readable your files from private data/data directory use content providers.

You can not write data inside asset_folder because it is packed on apk file. You can use sd card or location where your app is installed inside internal memory.

Record and playback a sound on Android without storing a temporary file

In my app I want to record a 2-second long sound and play it back to the user. All examples I've found so far require that the audio data for playback either comes from a file or from a URL.
Both MediaPlayer and SoundPool classes accept only files, file descriptors, resource id's or URLs as input and not just, say, a byte array.
Since one can only write files to the SD card and NOT internal storage (is this so?), the app would require that an SD card is mounted and writable. But my app should also work if no SD card is present.
Is there a way to achieve this?
Thanks

Yes, an App can write to internal storage (where it is installed). Every Installed app is provided a Data folder to write its internal files. Also there is a cache storage provided.
These methods of Context can get you these directories:
getCacheDir() : Returns the absolute path to the application specific cache directory on the filesystem (Note: System may delete cache if its low on storage)
getDir(String name, int mode) : Retrieve, creating if needed, a new directory in which the application can place its own custom data files.
Also there is a method for External storage: getExternalCacheDir() but is unreliable since external storage might not be always there.
Also, if you just need to write files in App's internal data directory, there is a very simple method:
openFileOutput (String name, int mode)

You can use
'getApplicationContext().getFilesDir().getAbsolutePath()'
to get the path of the directory where the app is installed.
One limitation is, 'getFilesDir()' gives you the path to the directory on the file system where files created with openFileOutput(String, int) are stored.

How to create private folder in sdcard

My application is used for security purpose. so, from my application user captures photos that all photos are stored in a folder that folder should not access from any other application and should not give access when devices connect to computer system. If user wants to view these images he should access only from my application.

According to this guide, you can save files directly on the device's internal storage. By default, files saved to the internal storage are private to your application and other applications cannot access them (nor can the user). When the user uninstalls your application, these files are removed.
For example:
String FILENAME = "hello_file";
String string = "hello world!";
FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
fos.write(string.getBytes());
fos.close();
MODE_PRIVATE will create the file (or replace a file of the same name) and make it private to your application. Other modes available are: MODE_APPEND, MODE_WORLD_READABLE, and MODE_WORLD_WRITEABLE.

The only way, AFAIK is to encrypt the files that you store. There is no way to prevent users mount the sdcard to access every file stored in it.

according to this related question, you can only create protected files in internal storage (not on the SD)...
Create Folder that can not accessible by any other application

Try following solution:
How to store a file in Hidden mode
Although it is not exactly what you want and I doubt whether it is possible or not. The best option would be to make it hidden but that also works with constraint (works for linux and not for Windows, still other applications can access the folder)
How to hide the folder of sdcard in android
How to make a file hidden in android sd card?

Its not possible to give no access to that folder when device connected to pc.. Also its not possible on sdcard also,
But you can use different format for images that can be opened only from your application, or you can encrypt images.
Or if you want to hide images from showing them into gallery, you can put a blank file with name as ".nomedia" in your folder.
But its not possible cause if u read docs about WRITE_EXTERNEL_STORAGE permission you will understand what I am saying. :)

Android: Delete app associated files from external storage on Uninstall?

It'd be convenient if an application I'm writing stored some files to external storage permanently (so they persist after the application has been exited[destroyed]), but on an uninstall I'd like to do the decent thing and have these files removed to free up the storage.
Is there any way I can have these files removed on an uninstall?
If there isn't (and I'm skeptical), then I'll have to create these files each time. I'm trying to save start-up time and also occupy required space by having them exist permanently.
Note: I need to use external storage, so both internal storage or a DB would be inappropriate.

actually it is possible .
android will automatically remove files of the app in the external storage , but the files must be inside a specific path of the app :
"...../Android/data/APP_PACKAGE_NAME/"
where APP_PACKAGE_NAME is the application's package name.
another path that is automatically being emptied is :
"...../Android/obb/APP_PACKAGE_NAME/"
where APP_PACKAGE_NAME is the application's package name.
the data is for anything you wish.
the obb folder is for huge files that are downloaded using the play-store and the apk extension library . you are not supposed to create files there .

No, I don't believe so. Only files that you write to internal storage will be removed when your application is uninstalled (or if the user presses the 'clear data' button in the Application settings app).
Your app can't receive its own PACKAGE_REMOVED broadcast intent either, so you essentially have no notification that you're being uninstalled.

Yes, this is possible. Simply write your files to the external files directory:
File dir = getExternalFilesDir(null);
This will create a folder at /Android/data/your.package/. Note that this is not External as in sdcard, but it is publicly accessible. If a user uninstalls your app, this directory will also be removed, along with all of its contents.

Quoting from the blog post of CommonsWare
Internal storage: your file is deleted
External storage: if you wrote your file to a location rooted at getExternalFilesDir() or getExternalCacheDir(), your file is deleted. If you wrote your file elsewhere (e.g., Environment.getExternalStoragePublicDirectory()), your file is not deleted
Removable storage, prior to Android 4.4: removable storage is not officially accessible; if your file winds up out there, it should not be deleted when your app is uninstalled
Removable storage, Android 4.4+: AFAIK, if you write to a supported location (getExternalFilesDirs() or getExternalCacheDirs()), your file is deleted if that particular bit of removable storage is in the device at the time of uninstall