Everything about storage on Android

Understanding Storage on Android

Overview of Android Storage Architecture

• Yacine Rezgui introduces the topic of storage on Android, focusing on APIs and best practices.

• The primary storage volume is where the OS and apps are located; it includes internal storage that is private to each app for confidential data like databases.

• External storage allows for app-specific files but can be limited by device capacity; sensitive information should not be stored here due to accessibility by other apps before Android 11.

• Shared storage is accessible by all apps, allowing users to see files in file managers and galleries; files remain after app uninstallation.

• MediaStore indexes shared storage content, providing efficient access to media file metadata.

Scoped Storage Changes

• Scoped storage was introduced in Android 10, restricting access to shared files based on file type (e.g., only media files without permissions).

• WRITE_EXTERNAL_STORAGE permission is deprecated; user consent is now required for modifying or deleting media files.

• Location metadata for media files is removed automatically; developers must request access separately if needed.

Common Use Cases for Storage

Downloading User Data

• For downloading confidential user data, OkHttp library is used to create HTTPS requests and save responses securely in internal storage.

• When downloading large non-confidential assets, check available space first in internal storage before using external options if necessary.

Adding Files to Shared Storage

• To add images or videos to shared storage, permissions were previously required up until Android 9; this changed with scoped storage from Android 10 onwards.

• Use environment constants (like DIRECTORY_PICTURES or DIRECTORY_MOVIES) when saving different types of files into appropriate folders within shared storage.

Scanning Files into MediaStore

Enhancements in File Access and Media Selection on Android

Utilizing the OpenDocument Intent

• The document picker is accessed via the action OpenDocument intent, requiring the addition of Jetpack Activity dependency to the project.

• Registration of the OpenDocument activity result is necessary to handle intent resolution logic for file selection.

• Upon user selection, a URI can be obtained to open files using the content resolver, specifically filtering for PDF MIME types.

• The action OpenDocument intent is compatible with devices running Android 4.4 (KitKat) and higher.

Transitioning from External Storage Permissions

• Prior to Android 13, accessing shared storage required read external storage permissions and custom UI implementations for item selection.

• A simpler and more privacy-friendly approach was sought for developers and users alike.

Introduction of Photo Picker in Android 13

• Android 13 introduced a photo picker that enhances user experience by allowing image and video selection without runtime permissions.

• This feature is maintenance-free, enabling developers to limit selectable items with minimal code integration; it’s backported to Android 11 and 12.

• Upcoming support for cloud media providers like Google Photos will allow access to backed-up photos/videos not stored locally on devices.

Implementing Visual Media Selection

• To utilize the photo picker, add Jetpack Activity dependency version 1.6 or higher; register PickVisualMedia activity result for handling intents.

• The implementation allows fallback to document picker on older devices while providing URIs for selected files through content resolver access.

New Permissions and Privacy Improvements in Android 13

• For persistent file access post-app closure, developers can use takePersistableUriPermission; this is useful for applications like gallery backups.

• New permissions targeting API level 33 provide specific access rights for media files including images, videos, or audio.