Android studio save file to downloads

Saving Files

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Android uses a file system that’s similar to disk-based file systems on other platforms. This lesson describes how to work with the Android file system to read and write files with the File APIs.

A File object is suited to reading or writing large amounts of data in start-to-finish order without skipping around. For example, it’s good for image files or anything exchanged over a network.

This lesson shows how to perform basic file-related tasks in your app. The lesson assumes that you are familiar with the basics of the Linux file system and the standard file input/output APIs in java.io .

Choose Internal or External Storage

All Android devices have two file storage areas: «internal» and «external» storage. These names come from the early days of Android, when most devices offered built-in non-volatile memory (internal storage), plus a removable storage medium such as a micro SD card (external storage). Some devices divide the permanent storage space into «internal» and «external» partitions, so even without a removable storage medium, there are always two storage spaces and the API behavior is the same whether the external storage is removable or not. The following lists summarize the facts about each storage space.

• It’s always available.
• Files saved here are accessible by only your app by default.
• When the user uninstalls your app, the system removes all your app’s files from internal storage.

Internal storage is best when you want to be sure that neither the user nor other apps can access your files.

• It’s not always available, because the user can mount the external storage as USB storage and in some cases remove it from the device.
• It’s world-readable, so files saved here may be read outside of your control.
• When the user uninstalls your app, the system removes your app’s files from here only if you save them in the directory from getExternalFilesDir() .

External storage is the best place for files that don’t require access restrictions and for files that you want to share with other apps or allow the user to access with a computer.

Tip: Although apps are installed onto the internal storage by default, you can specify the android:installLocation attribute in your manifest so your app may be installed on external storage. Users appreciate this option when the APK size is very large and they have an external storage space that’s larger than the internal storage. For more information, see App Install Location.

Obtain Permissions for External Storage

To write to the external storage, you must request the WRITE_EXTERNAL_STORAGE permission in your manifest file:

Caution: Currently, all apps have the ability to read the external storage without a special permission. However, this will change in a future release. If your app needs to read the external storage (but not write to it), then you will need to declare the READ_EXTERNAL_STORAGE permission. To ensure that your app continues to work as expected, you should declare this permission now, before the change takes effect.

However, if your app uses the WRITE_EXTERNAL_STORAGE permission, then it implicitly has permission to read the external storage as well.

You don’t need any permissions to save files on the internal storage. Your application always has permission to read and write files in its internal storage directory.

Save a File on Internal Storage

When saving a file to internal storage, you can acquire the appropriate directory as a File by calling one of two methods:

getFilesDir() Returns a File representing an internal directory for your app. getCacheDir() Returns a File representing an internal directory for your app’s temporary cache files. Be sure to delete each file once it is no longer needed and implement a reasonable size limit for the amount of memory you use at any given time, such as 1MB. If the system begins running low on storage, it may delete your cache files without warning.

To create a new file in one of these directories, you can use the File() constructor, passing the File provided by one of the above methods that specifies your internal storage directory. For example:

Alternatively, you can call openFileOutput() to get a FileOutputStream that writes to a file in your internal directory. For example, here’s how to write some text to a file:

Or, if you need to cache some files, you should instead use createTempFile() . For example, the following method extracts the file name from a URL and creates a file with that name in your app’s internal cache directory:

Note: Your app’s internal storage directory is specified by your app’s package name in a special location of the Android file system. Technically, another app can read your internal files if you set the file mode to be readable. However, the other app would also need to know your app package name and file names. Other apps cannot browse your internal directories and do not have read or write access unless you explicitly set the files to be readable or writable. So as long as you use MODE_PRIVATE for your files on the internal storage, they are never accessible to other apps.

Save a File on External Storage

Because the external storage may be unavailable—such as when the user has mounted the storage to a PC or has removed the SD card that provides the external storage—you should always verify that the volume is available before accessing it. You can query the external storage state by calling getExternalStorageState() . If the returned state is equal to MEDIA_MOUNTED , then you can read and write your files. For example, the following methods are useful to determine the storage availability:

Although the external storage is modifiable by the user and other apps, there are two categories of files you might save here:

Public files Files that should be freely available to other apps and to the user. When the user uninstalls your app, these files should remain available to the user.

For example, photos captured by your app or other downloaded files.

Private files Files that rightfully belong to your app and should be deleted when the user uninstalls your app. Although these files are technically accessible by the user and other apps because they are on the external storage, they are files that realistically don’t provide value to the user outside your app. When the user uninstalls your app, the system deletes all files in your app’s external private directory.

For example, additional resources downloaded by your app or temporary media files.

If you want to save public files on the external storage, use the getExternalStoragePublicDirectory() method to get a File representing the appropriate directory on the external storage. The method takes an argument specifying the type of file you want to save so that they can be logically organized with other public files, such as DIRECTORY_MUSIC or DIRECTORY_PICTURES . For example:

If you want to save files that are private to your app, you can acquire the appropriate directory by calling getExternalFilesDir() and passing it a name indicating the type of directory you’d like. Each directory created this way is added to a parent directory that encapsulates all your app’s external storage files, which the system deletes when the user uninstalls your app.

For example, here’s a method you can use to create a directory for an individual photo album:

If none of the pre-defined sub-directory names suit your files, you can instead call getExternalFilesDir() and pass null . This returns the root directory for your app’s private directory on the external storage.

Remember that getExternalFilesDir() creates a directory inside a directory that is deleted when the user uninstalls your app. If the files you’re saving should remain available after the user uninstalls your app—such as when your app is a camera and the user will want to keep the photos—you should instead use getExternalStoragePublicDirectory() .

Regardless of whether you use getExternalStoragePublicDirectory() for files that are shared or getExternalFilesDir() for files that are private to your app, it’s important that you use directory names provided by API constants like DIRECTORY_PICTURES . These directory names ensure that the files are treated properly by the system. For instance, files saved in DIRECTORY_RINGTONES are categorized by the system media scanner as ringtones instead of music.

Query Free Space

If you know ahead of time how much data you’re saving, you can find out whether sufficient space is available without causing an IOException by calling getFreeSpace() or getTotalSpace() . These methods provide the current available space and the total space in the storage volume, respectively. This information is also useful to avoid filling the storage volume above a certain threshold.

However, the system does not guarantee that you can write as many bytes as are indicated by getFreeSpace() . If the number returned is a few MB more than the size of the data you want to save, or if the file system is less than 90% full, then it’s probably safe to proceed. Otherwise, you probably shouldn’t write to storage.

Note: You aren’t required to check the amount of available space before you save your file. You can instead try writing the file right away, then catch an IOException if one occurs. You may need to do this if you don’t know exactly how much space you need. For example, if you change the file’s encoding before you save it by converting a PNG image to JPEG, you won’t know the file’s size beforehand.

Delete a File

You should always delete files that you no longer need. The most straightforward way to delete a file is to have the opened file reference call delete() on itself.

If the file is saved on internal storage, you can also ask the Context to locate and delete a file by calling deleteFile() :

Note: When the user uninstalls your app, the Android system deletes the following:

• All files you saved on internal storage
• All files you saved on external storage using getExternalFilesDir() .

However, you should manually delete all cached files created with getCacheDir() on a regular basis and also regularly delete other files you no longer need.

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Access media files from shared storage

To provide a more enriched user experience, many apps allow users to contribute and access media that’s available on an external storage volume. The framework provides an optimized index into media collections, called the media store, that allows for retrieving and updating these media files more easily. Even after your app is uninstalled, these files remain on the user’s device.

To interact with the media store abstraction, use a ContentResolver object that you retrieve from your app’s context:

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The system automatically scans an external storage volume and adds media files to the following well-defined collections:

• Images, including photographs and screenshots, which are stored in the DCIM/ and Pictures/ directories. The system adds these files to the MediaStore.Images table.
• Videos, which are stored in the DCIM/ , Movies/ , and Pictures/ directories. The system adds these files to the MediaStore.Video table.
• Audio files, which are stored in the Alarms/ , Audiobooks/ , Music/ , Notifications/ , Podcasts/ , and Ringtones/ directories. Additionally, the system recognizes audio playlists that are in the Music/ or Movies/ directories, as well as voice recordings that are in the Recordings/ directory. The system adds these files to the MediaStore.Audio table. The recordings directory isn’t available on Android 11 (API level 30) and lower.
• Downloaded files, which are stored in the Download/ directory. On devices that run Android 10 (API level 29) and higher, these files are stored in the MediaStore.Downloads table. This table isn’t available on Android 9 (API level 28) and lower.

The media store also includes a collection called MediaStore.Files . Its contents depend on whether your app uses scoped storage, available on apps that target Android 10 or higher:

• If scoped storage is enabled, the collection shows only the photos, videos, and audio files that your app has created. Most developers won’t need to use MediaStore.Files to view media files from other apps, but if you have a specific requirement to do so, you can declare the READ_EXTERNAL_STORAGE permission. It’s recommended, however, that you use the MediaStore APIs to open files that your app hasn’t created.
• If scoped storage is unavailable or not being used, the collection shows all types of media files.

Request necessary permissions

Before performing operations on media files, make sure your app has declared the permissions that it needs to access these files. Keep in mind, however, that your app shouldn’t declare permissions that it doesn’t need or use.

Storage permission

The permissions model for accessing media files in your app depends on whether your app uses scoped storage, available on apps that target Android 10 or higher.

Scoped storage enabled

If your app uses scoped storage, it should request storage-related permissions only for devices that run Android 9 (API level 28) or lower. You can apply this condition by adding the android:maxSdkVersion attribute to the permission declaration in your app’s manifest file:

Don’t unnecessarily request storage-related permissions for devices that run Android 10 or higher. Your app can contribute to well-defined media collections, including the MediaStore.Downloads collection, without requesting any storage-related permissions. If you’re developing a camera app, for example, you don’t need to request storage-related permissions because your app owns the images that you’re writing to the media store.

To access files that other apps have created, the following conditions must each be true:

If your app wants to access a file within the MediaStore.Downloads collection that your app didn’t create, you must use the Storage Access Framework. To learn more about how to use this framework, see the guide on how to access documents and other files.

Scoped storage unavailable

If your app is used on a device that runs Android 9 or lower, or if your app has temporarily opted out of scoped storage, you must request the READ_EXTERNAL_STORAGE permission to access media files. If you want to modify media files, you must request the WRITE_EXTERNAL_STORAGE permission, as well.

Media location permission

If your app targets Android 10 (API level 29) or higher, in order for your app to retrieve unredacted Exif metadata from photos, you need to declare the ACCESS_MEDIA_LOCATION permission in your app’s manifest, then request this permission at runtime.

Check for updates to the media store

To access media files more reliably, particularly if your app caches URIs or data from the media store, check whether the media store version has changed compared to when you last synced your media data. To perform this check for updates, call getVersion() . The returned version is a unique string that changes whenever the media store changes substantially. If the returned version is different from the last synced version, rescan and resync your app’s media cache.

Complete this check at app process startup time. There’s no need to check the version each time you query the media store.

Don’t assume any implementation details regarding the version number.

Query a media collection

To find media that satisfies a particular set of conditions, such as a duration of 5 minutes or longer, use an SQL-like selection statement similar to the one shown in the following code snippet:

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When performing such a query in your app, keep the following in mind:

• Call the query() method in a worker thread.
• Cache the column indices so that you don’t need to call getColumnIndexOrThrow() each time you process a row from the query result.
• Append the ID to the content URI, as shown in the code snippet.
• Devices that run Android 10 and higher require column names that are defined in the MediaStore API. If a dependent library within your app expects a column name that’s undefined in the API, such as «MimeType» , use CursorWrapper to dynamically translate the column name in your app’s process.

Load file thumbnails

If your app shows multiple media files and requests that the user choose one of these files, it’s more efficient to load preview versions—or thumbnails—of the files instead of the files themselves.

To load the thumbnail for a given media file, use loadThumbnail() and pass in the size of the thumbnail that you want to load, as shown in the following code snippet:

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Open a media file

The specific logic that you use to open a media file depends on whether the media content is best represented as a file descriptor, a file stream, or a direct file path:

File descriptor

To open a media file using a file descriptor, use logic similar to that shown in the following code snippet:

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File stream

To open a media file using a file stream, use logic similar to that shown in the following code snippet:

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Direct file paths

To help your app work more smoothly with third-party media libraries, Android 11 (API level 30) and higher allow you to use APIs other than the MediaStore API to access media files from shared storage. You can instead access media files directly using either of the following APIs:

• The File API.
• Native libraries, such as fopen() .

If you don’t have any storage-related permissions, you can access files in your app-specific directory, as well as media files that are attributed to your app, using the File API.

If your app tries to access a file using the File API and it doesn’t have the necessary permissions, a FileNotFoundException occurs.

To access other files in shared storage on a device that runs Android 10 (API level 29), it’s recommended that you temporarily opt out of scoped storage by setting requestLegacyExternalStorage to true in your app’s manifest file. In order to access media files using native files methods on Android 10, you must also request the READ_EXTERNAL_STORAGE permission.

Considerations when accessing media content

When accessing media content, keep in mind the considerations discussed in the following sections.

Cached data

If your app caches URIs or data from the media store, periodically check for updates to the media store. This check allows your app-side, cached data to stay in sync with the system-side, provider data.

Performance

When you perform sequential reads of media files using direct file paths, the performance is comparable to that of the MediaStore API.

When you perform random reads and writes of media files using direct file paths, however, the process can be up to twice as slow. In these situations, we recommend using the MediaStore API instead.

DATA column

When you access an existing media file, you can use the value of the DATA column in your logic. That’s because this value has a valid file path. However, don’t assume that the file is always available. Be prepared to handle any file-based I/O errors that could occur.

To create or update a media file, on the other hand, don’t use the value of the DATA column. Instead, use the values of the DISPLAY_NAME and RELATIVE_PATH columns.

Storage volumes

Apps that target Android 10 or higher can access the unique name that the system assigns to each external storage volume. This naming system helps you efficiently organize and index content, and it gives you control over where new media files are stored.

The following volumes are particularly useful to keep in mind:

• The VOLUME_EXTERNAL volume provides a view of all shared storage volumes on the device. You can read the contents of this synthetic volume, but you cannot modify the contents.
• The VOLUME_EXTERNAL_PRIMARY volume represents the primary shared storage volume on the device. You can read and modify the contents of this volume.

You can discover other volumes by calling MediaStore.getExternalVolumeNames() :

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Location where media was captured

Some photographs and videos contain location information in their metadata, which shows the place where a photograph was taken or where a video was recorded.

To access this location information in your app, use one API for photograph location information and another API for video location information.

Photographs

If your app uses scoped storage, the system hides location information by default. To access this information, complete the following steps:

Request the ACCESS_MEDIA_LOCATION permission in your app’s manifest.

From your MediaStore object, get the exact bytes of the photograph by calling setRequireOriginal() and pass in the URI of the photograph, as shown in the following code snippet:

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Videos

To access location information within a video’s metadata, use the MediaMetadataRetriever class, as shown in the following code snippet. Your app doesn’t need to request any additional permissions to use this class.

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Sharing

Some apps allow users to share media files with each other. For example, social media apps give users the ability to share photos and videos with friends.

To share media files, use a content:// URI, as recommended in the guide to creating a content provider.

App attribution of media files

When scoped storage is enabled for an app that targets Android 10 or higher, the system attributes an app to each media file, which determines the files that your app can access when it hasn’t requested any storage permissions. Each file can be attributed to only one app. Therefore, if your app creates a media file that’s stored in the photos, videos, or audio files media collection, your app has access to the file.

If the user uninstalls and reinstalls your app, however, you must request READ_EXTERNAL_STORAGE to access the files that your app originally created. This permission request is required because the system considers the file to be attributed to the previously-installed version of the app, rather than the newly-installed one.

Add an item

To add a media item to an existing collection, call code similar to the following. This code snippet accesses the VOLUME_EXTERNAL_PRIMARY volume on devices that run Android 10 or higher. That’s because, on these devices, you can only modify the contents of a volume if it’s the primary volume, as described in the storage volumes section.

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Toggle pending status for media files

If your app performs potentially time-consuming operations, such as writing to media files, it’s useful to have exclusive access to the file as it’s being processed. On devices that run Android 10 or higher, your app can get this exclusive access by setting the value of the IS_PENDING flag to 1. Only your app can view the file until your app changes the value of IS_PENDING back to 0.

The following code snippet builds upon the previous code snippet. The following snippet shows how to use the IS_PENDING flag when storing a long song in the directory corresponding to the MediaStore.Audio collection:

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Give a hint for file location

When your app stores media on a device running Android 10, the media is organized based on its type by default. For example, new image files are placed by default in the Environment.DIRECTORY_PICTURES directory, which corresponds to the MediaStore.Images collection.

If your app is aware of a specific location where files should be stored, such as a photo album called Pictures/MyVacationPictures, you can set MediaColumns.RELATIVE_PATH to provide the system a hint for where to store the newly-written files.

Update an item

To update a media file that your app owns, run code similar to the following:

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If scoped storage is unavailable or not enabled, the process shown in the preceding code snippet also works for files that your app doesn’t own.

Update in native code

If you need to write media files using native libraries, pass the file’s associated file descriptor from your Java-based or Kotlin-based code into your native code.

The following code snippet shows how to pass a media object’s file descriptor into your app’s native code:

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Update other apps’ media files

If your app uses scoped storage, it ordinarily cannot update a media file that a different app contributed to the media store.

It’s still possible to get user consent to modify the file, however, by catching the RecoverableSecurityException that the platform throws. You can then request that the user grant your app write access to that specific item, as shown in the following code snippet:

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Complete this process each time your app needs to modify a media file that it didn’t create.

Alternatively, if your app runs on Android 11 or higher, you can allow users to grant your app write access to a group of media files. Call the createWriteRequest() method, as described in the section on how to manage groups of media files.

If your app has another use case that isn’t covered by scoped storage, file a feature request and temporarily opt out of scoped storage.

Remove an item

To remove an item that your app no longer needs in the media store, use logic similar to what’s shown in the following code snippet:

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If scoped storage is unavailable or isn’t enabled, you can use the preceding code snippet to remove files that other apps own. If scoped storage is enabled, however, you need to catch a RecoverableSecurityException for each file that your app wants to remove, as described in the section on updating media items.

If your app runs on Android 11 or higher, you can allow users to choose a group of media files to remove. Call the createTrashRequest() method or the createDeleteRequest() method, as described in the section on how to manage groups of media files.

If your app has another use case that isn’t covered by scoped storage, file a feature request and temporarily opt out of scoped storage.

Detect updates to media files

Your app might need to identify storage volumes containing media files that apps added or modified, compared to a previous point in time. To detect these changes most reliably, pass the storage volume of interest into getGeneration() . As long as the media store version doesn’t change, the return value of this method monotonically increases over time.

In particular, getGeneration() is more robust than the dates in media columns, such as DATE_ADDED and DATE_MODIFIED . That’s because those media column values could change when an app calls setLastModified() , or when the user changes the system clock.

Manage groups of media files

On Android 11 and higher, you can ask the user to select a group of media files, then update these media files in a single operation. These methods offer better consistency across devices, and the methods make it easier for users to manage their media collections.

The methods that provide this «batch update» functionality include the following:

createWriteRequest() Request that the user grant your app write access to the specified group of media files. createFavoriteRequest() Request that the user marks the specified media files as some of their «favorite» media on the device. Any app that has read access to this file can see that the user has marked the file as a «favorite». createTrashRequest()

Request that the user place the specified media files in the device’s trash. Items in the trash are permanently deleted after a system-defined time period.

Request that the user permanently delete the specified media files immediately, without placing them in the trash beforehand.

After calling any of these methods, the system builds a PendingIntent object. After your app invokes this intent, users see a dialog that requests their consent for your app to update or delete the specified media files.

For example, here is how to structure a call to createWriteRequest() :

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Evaluate the user’s response. If the user provided consent, proceed with the media operation. Otherwise, explain to the user why your app needs the permission:

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Media management permission

Users might trust a particular app to perform media management, such as making frequent edits to media files. If your app targets Android 11 or higher and isn’t the device’s default gallery app, you must show a confirmation dialog to the user each time your app attempts to modify or delete a file.

If your app targets Android 12 (API level 31) or higher, you can request that users grant your app access to the Media management special permission. This permission allows your app to do each of the following without needing to prompt the user for each file operation:

To do so, complete the following steps:

Declare the MANAGE_MEDIA permission and the READ_EXTERNAL_STORAGE permission in your app’s manifest file.

In order to call createWriteRequest() without showing a confirmation dialog, declare the ACCESS_MEDIA_LOCATION permission as well.

In your app, show a UI to the user to explain why they might want to grant media management access to your app.

Invoke the ACTION_REQUEST_MANAGE_MEDIA intent action. This takes users to the Media management apps screen in system settings. From here, users can grant the special app access.

Use cases that require an alternative to media store

If your app primarily performs one of the following roles, consider an alternative to the MediaStore APIs.

Work with other types of files

If your app works with documents and files that don’t exclusively contain media content, such as files that use the EPUB or PDF file extension, use the ACTION_OPEN_DOCUMENT intent action, as described in the guide on how to store and access documents and other files.

File sharing in companion apps

In cases where you provide a suite of companion apps—such as a messaging app and a profile app—set up file sharing using content:// URIs. We also recommend this workflow as a security best practice.

Additional resources

For more information about how to store and access media, consult the following resources.

Samples

Videos

Content and code samples on this page are subject to the licenses described in the Content License. Java is a registered trademark of Oracle and/or its affiliates.

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