FileProvider

<init>

FileProvider()

FileProvider is a special subclass of ContentProvider that facilitates secure sharing of files associated with an app by creating a content://Uri for a file instead of a file:///Uri

A content URI allows you to grant read and write access using temporary access permissions. When you create an Intent containing a content URI, in order to send the content URI to a client app, you can also call Intent.setFlags() to add permissions. These permissions are available to the client app for as long as the stack for a receiving android.app.Activity is active. For an Intent going to a android.app.Service, the permissions are available as long as the android.app.Service is running.

In comparison, to control access to a file:/// Uri you have to modify the file system permissions of the underlying file. The permissions you provide become available to any app, and remain in effect until you change them. This level of access is fundamentally insecure.

The increased level of file access security offered by a content URI makes FileProvider a key part of Android's security infrastructure.

This overview of FileProvider includes the following topics:

1. Defining a FileProvider
2. Specifying Available Files
3. Retrieving the Content URI for a File
4. Granting Temporary Permissions to a URI
5. Serving a Content URI to Another App

Defining a FileProvider

Since the default functionality of FileProvider includes content URI generation for files, you don't need to define a subclass in code. Instead, you can include a FileProvider in your app by specifying it entirely in XML. To specify the FileProvider component itself, add a <provider> element to your app manifest. Set the android:name attribute to androidx.core.content.FileProvider. Set the android:authorities attribute to a URI authority based on a domain you control; for example, if you control the domain mydomain.com you should use the authority com.mydomain.fileprovider. Set the android:exported attribute to false; the FileProvider does not need to be public. Set the android:grantUriPermissions attribute to true, to allow you to grant temporary access to files. For example:

<manifest>
     ...
     <application>
         ...
         <provider
             android:name="androidx.core.content.FileProvider"
             android:authorities="com.mydomain.fileprovider"
             android:exported="false"
             android:grantUriPermissions="true">
             ...
         </provider>
         ...
     </application>
 </manifest>

If you want to override any of the default behavior of FileProvider methods, extend the FileProvider class and use the fully-qualified class name in the android:name attribute of the <provider> element.

Specifying Available Files

<paths xmlns:android="http://schemas.android.com/apk/res/android">
     <files-path name="my_images" path="images/"/>
     ...
 </paths>
 

The <paths> element must contain one or more of the following child elements:

<files-path name="<i>name</i>" path="<i>path</i>" />
 

Represents files in the files/ subdirectory of your app's internal storage area. This subdirectory is the same as the value returned by Context.getFilesDir().

<cache-path name="<i>name</i>" path="<i>path</i>" />
 

Represents files in the cache subdirectory of your app's internal storage area. The root path of this subdirectory is the same as the value returned by getCacheDir().

<external-path name="<i>name</i>" path="<i>path</i>" />
 

Represents files in the root of the external storage area. The root path of this subdirectory is the same as the value returned by Environment.getExternalStorageDirectory().

<external-files-path name="<i>name</i>" path="<i>path</i>" />
 

Represents files in the root of your app's external storage area. The root path of this subdirectory is the same as the value returned by Context#getExternalFilesDir(String) Context.getExternalFilesDir(null).

<external-cache-path name="<i>name</i>" path="<i>path</i>" />
 

Represents files in the root of your app's external cache area. The root path of this subdirectory is the same as the value returned by Context.getExternalCacheDir().

<external-media-path name="<i>name</i>" path="<i>path</i>" />
 

Represents files in the root of your app's external media area. The root path of this subdirectory is the same as the value returned by the first result of Context.getExternalMediaDirs().

Note: this directory is only available on API 21+ devices.

These child elements all use the same attributes:

name="name"

A URI path segment. To enforce security, this value hides the name of the subdirectory you're sharing. The subdirectory name for this value is contained in the path attribute.

path="path"

The subdirectory you're sharing. While the name attribute is a URI path segment, the path value is an actual subdirectory name. Notice that the value refers to a subdirectory, not an individual file or files. You can't share a single file by its file name, nor can you specify a subset of files using wildcards.

You must specify a child element of <paths> for each directory that contains files for which you want content URIs. For example, these XML elements specify two directories:

<paths xmlns:android="http://schemas.android.com/apk/res/android">
     <files-path name="my_images" path="images/"/>
     <files-path name="my_docs" path="docs/"/>
 </paths>
 

Put the <paths> element and its children in an XML file in your project. For example, you can add them to a new file called res/xml/file_paths.xml. To link this file to the FileProvider, add a <meta-data> element as a child of the <provider> element that defines the FileProvider. Set the <meta-data> element's "android:name" attribute to android.support.FILE_PROVIDER_PATHS. Set the element's "android:resource" attribute to @xml/file_paths (notice that you don't specify the .xml extension). For example:

<provider
     android:name="androidx.core.content.FileProvider"
     android:authorities="com.mydomain.fileprovider"
     android:exported="false"
     android:grantUriPermissions="true">
     <meta-data
         android:name="android.support.FILE_PROVIDER_PATHS"
         android:resource="@xml/file_paths" />
 </provider>
 

Generating the Content URI for a File

To share a file with another app using a content URI, your app has to generate the content URI. To generate the content URI, create a new File for the file, then pass the File to getUriForFile(). You can send the content URI returned by getUriForFile() to another app in an android.content.Intent. The client app that receives the content URI can open the file and access its contents by calling ContentResolver.openFileDescriptor to get a ParcelFileDescriptor.

For example, suppose your app is offering files to other apps with a FileProvider that has the authority com.mydomain.fileprovider. To get a content URI for the file default_image.jpg in the images/ subdirectory of your internal storage add the following code:

File imagePath = new File(Context.getFilesDir(), "images");
 File newFile = new File(imagePath, "default_image.jpg");
 Uri contentUri = getUriForFile(getContext(), "com.mydomain.fileprovider", newFile);
 

Granting Temporary Permissions to a URI

• Call the method Context.grantUriPermission(package, Uri, mode_flags) for the content:// Uri, using the desired mode flags. This grants temporary access permission for the content URI to the specified package, according to the value of the the mode_flags parameter, which you can set to Intent#FLAG_GRANT_READ_URI_PERMISSION, Intent#FLAG_GRANT_WRITE_URI_PERMISSION or both. The permission remains in effect until you revoke it by calling revokeUriPermission() or until the device reboots.
• Put the content URI in an Intent by calling setData().
• Next, call the method Intent.setFlags() with either Intent#FLAG_GRANT_READ_URI_PERMISSION or Intent#FLAG_GRANT_WRITE_URI_PERMISSION or both.
• Finally, send the Intent to another app. Most often, you do this by calling setResult().

  Permissions granted in an Intent remain in effect while the stack of the receiving android.app.Activity is active. When the stack finishes, the permissions are automatically removed. Permissions granted to one android.app.Activity in a client app are automatically extended to other components of that app.

Serving a Content URI to Another App

There are a variety of ways to serve the content URI for a file to a client app. One common way is for the client app to start your app by calling android.app.Activity#startActivityForResult(Intent, int, Bundle), which sends an Intent to your app to start an android.app.Activity in your app. In response, your app can immediately return a content URI to the client app or present a user interface that allows the user to pick a file. In the latter case, once the user picks the file your app can return its content URI. In both cases, your app returns the content URI in an Intent sent via setResult().

You can also put the content URI in a android.content.ClipData object and then add the object to an Intent you send to a client app. To do this, call Intent#setClipData(ClipData). When you use this approach, you can add multiple android.content.ClipData objects to the Intent, each with its own content URI. When you call Intent.setFlags() on the Intent to set temporary access permissions, the same permissions are applied to all of the content URIs.

Note: The Intent#setClipData(ClipData) method is only available in platform version 16 (Android 4.1) and later. If you want to maintain compatibility with previous versions, you should send one content URI at a time in the Intent. Set the action to Intent#ACTION_SEND and put the URI in data by calling setData().

More Information

To learn more about FileProvider, see the Android training class Sharing Files Securely with URIs.

attachInfo

open fun attachInfo(
    @NonNull context: Context, 
    @NonNull info: ProviderInfo
): Unit

After the FileProvider is instantiated, this method is called to provide the system with information about the provider.

delete

open fun delete(
    @NonNull uri: Uri, 
    @Nullable selection: String?, 
    @Nullable selectionArgs: Array<String!>?
): Int

Deletes the file associated with the specified content URI, as returned by getUriForFile(). Notice that this method does not throw an java.io.IOException; you must check its return value.

getType

open fun getType(@NonNull uri: Uri): String?

Returns the MIME type of a content URI returned by getUriForFile().

getUriForFile

open static fun getUriForFile(
    @NonNull context: Context, 
    @NonNull authority: String, 
    @NonNull file: File
): Uri!

Return a content URI for a given File. Specific temporary permissions for the content URI can be set with Context#grantUriPermission(String, Uri, int), or added to an Intent by calling setData() and then setFlags(); in both cases, the applicable flags are Intent#FLAG_GRANT_READ_URI_PERMISSION and Intent#FLAG_GRANT_WRITE_URI_PERMISSION. A FileProvider can only return a content Uri for file paths defined in their <paths> meta-data element. See the Class Overview for more information.

insert

open fun insert(
    @NonNull uri: Uri, 
    values: ContentValues?
): Uri?

By default, this method throws an java.lang.UnsupportedOperationException. You must subclass FileProvider if you want to provide different functionality.

onCreate

open fun onCreate(): Boolean

The default FileProvider implementation does not need to be initialized. If you want to override this method, you must provide your own subclass of FileProvider.

openFile

open fun openFile(
    @NonNull uri: Uri, 
    @NonNull mode: String
): ParcelFileDescriptor?

By default, FileProvider automatically returns the ParcelFileDescriptor for a file associated with a content:// Uri. To get the ParcelFileDescriptor, call ContentResolver.openFileDescriptor. To override this method, you must provide your own subclass of FileProvider.

query

open fun query(
    @NonNull uri: Uri, 
    @Nullable projection: Array<String!>?, 
    @Nullable selection: String?, 
    @Nullable selectionArgs: Array<String!>?, 
    @Nullable sortOrder: String?
): Cursor?

Use a content URI returned by getUriForFile() to get information about a file managed by the FileProvider. FileProvider reports the column names defined in android.provider.OpenableColumns:

• android.provider.OpenableColumns#DISPLAY_NAME
• android.provider.OpenableColumns#SIZE

update

open fun update(
    @NonNull uri: Uri, 
    values: ContentValues?, 
    @Nullable selection: String?, 
    @Nullable selectionArgs: Array<String!>?
): Int

By default, this method throws an java.lang.UnsupportedOperationException. You must subclass FileProvider if you want to provide different functionality.