Some basics on Android storage system

From an Android point of view there are an → Internal Storage and an → External Storage.

1. Internal Storage
The Internal Storage can only be accessed with a rooted device.

1.1 The app package is saved in

/data/data/<packageName>/

1.2. The Private directory is

/data/user/0/<packageName>/files/

This private directory can be used with the File component to save / read text (setting the path without a slash). It can only be accessed by your app and is automatically removed when the app is uninstalled.

2. External Storage
The root directory of the External Storage is:

/storage/emulated/0/  or
file:///mnt/sdcard/ or
file:///storage/emulated/0/ 

To access the external storage, READ_ or WRITE_EXTERNAL_STORAGE permission is needed.

2.1. App-specific directory
In addition, there may be an app-specific directory (ASD) which can be created with

• Taifun’s File extension App Inventor Extensions: File | Pura Vida Apps or the
• FileTools extension FileTools : Some tools to work with files or
• Get the path of → ASD (app-specific dir) & → private data dir (internal storage) - Extensions - MIT App Inventor Community.

Note: The ASD seems always automatically be created by Kodular (not with AI2).
The path of the ASD is:

 /storage/emulated/0/Android/data/<packageName>/files/

which is in the External (private) Storage, but does not require READ_ / WRITE_EXTERNAL_STORAGE permissions. The ASD can only be accessed by your app and is automatically removed when the app is uninstalled.

See: Manifest.permission  |  Android Developers

2.2. External (removable / micro) SD card
There may also be another External Storage: a removable (micro) SD card, eg:

/storage/82C3-E96C/

that can only be read (on devices with Android ≥ 4.4 / KitKat, API 19).

Note:
The root directory of the External Storage

/storage/emulated/0/

is displayed on the device as Internal Storage (unfortunately this is a bit ambiguous).

When targeting Android ≥ 10

Scoped storage
To give users more control over their files and to limit file clutter, apps that target Android 10 (API level 29) and higher are given scoped access into external storage, or scoped storage, by default. Such apps have access only to the app-specific directory on external storage , as well as specific types of media that the app has created.

See also here (when Kodular has to target → Android 11, → Aug 2021):

Conclusion: Remember in good time to adjust your file paths accordingly.

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I would like to introduce these three basic terms:

Absolute path │ relative path │ full path

1. This path is an → absolute path:
/storage/emulated/0/Android/data/packageName/files/

2. This path is a → relative path:
/Android/data/packageName/files

Some components need a relative and others an absolute path.

3. And on top of that, some components or Android versions require a → full path:
file:///storage/emulated/0/Android/data/packageName/files/

I recommend these terms to distinguish the paths, for example:

• relative path: /Download
• absolute path: /storage/emulated/0/Download
• full path: file:///storage/emulated/0/Download

Storage Permissions on Android 10 & 11 - EDIT (May 11, 2022)
Since Kodular & AI2 decided to declare requestLegacyExternalStorage=true in the Manifest (which is only ignored on Android 11+), storage permissions must also be requested on Android 10.

If you remove this from the Manifest, which I would recommend, no permission for the Shared folders would be required on Android 10 either. The storage permissions would then have to be declared as follows:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="28" />

I generally prefer to request as few permissions as possible.
I don’t like permissions and my users even less.

What is this internal storage?

And this?

I am confused
I need to learn from you.

For more details see here:

It is only accessible to apps and you can’t view it unless you root your device.

Except internal storage other storage(either phone storage or sdCard) spaces fall in this category.
There are two types of it:

• Primary External Storage :- It is the phone storage.
• Secondary External Storage :- It is the sdCard.

And what about the otg…

OTG also come in Secondary External Storage category but is managed by USB Manager.

If supose we direct the app to download a file ,so by default it gets stored in the phone storage.[ By using this directory file:///storage/emulated/0/ …]
But if the phone storage is full will the app automatically detect and change its directory to External SD Card or we have to manually write the blocks for that ??

See here:

Oh I see,
So we have to do it manually ?

Yes, before you can access the removable SD card, you first have to get the path.

ok thx! ! !

Note: I just updated this guide.

I couldn’t do it myself , but @Peter made this topic a → Wiki.

How can I download files to this directory.

15 posts were split to a new topic: How to secure download files?

As far as I know, that is not possible. Only the File component can write in this dir.

Maybe he can download files in asd and copy them to private dir.

Thanks all for good support, I am happy with App-Specific Directory.
I used this extension, https://community.kodular.io/t/extension-to-download-file-s-to-asd-app-specific-directory-without-write-permission/96891/
Thank you so much for this extension also.

I’ve added a full overview of the Android storage system - Scoped / Shared Storage (targetSdk=30, Aug 2021) - at the end of my guide.

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Please, can anyone add in a guide some examples of code to save and read the files In mobiles with sdk 29 and 30 in a conditional way?