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FileProvider

public class FileProvider
extends ContentProvider

java.lang.Object
   ↳ android.content.ContentProvider
     ↳ android.support.v4.content.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 Activity is active. For an Intent going to a Service, the permissions are available as long as the 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 android.support.v4.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="android.support.v4.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

A FileProvider can only generate a content URI for files in directories that you specify beforehand. To specify a directory, specify the its storage area and path in XML, using child elements of the <paths> element. For example, the following paths element tells FileProvider that you intend to request content URIs for the images/ subdirectory of your private file area.
<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="name" path="path" />
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="name" path="path" />
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="name" path="path" />
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="name" path="path" />
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="name" path="path" />
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().

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="android.support.v4.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 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);
As a result of the previous snippet, getUriForFile() returns the content URI content://com.mydomain.fileprovider/my_images/default_image.jpg.

Granting Temporary Permissions to a URI

To grant an access permission to a content URI returned from getUriForFile(), do one of the following:

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 startActivityResult(), which sends an Intent to your app to start an 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 ClipData object and then add the object to an Intent you send to a client app. To do this, call Intent.setClipData(). When you use this approach, you can add multiple 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() 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 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.

Summary

Inherited constants

From interface android.content.ComponentCallbacks2

Public constructors

FileProvider()

Public methods

void attachInfo(Context context, ProviderInfo info)

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

int delete(Uri uri, String selection, String[] selectionArgs)

Deletes the file associated with the specified content URI, as returned by getUriForFile().

String getType(Uri uri)

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

static Uri getUriForFile(Context context, String authority, File file)

Return a content URI for a given File.

Uri insert(Uri uri, ContentValues values)

By default, this method throws an UnsupportedOperationException.

boolean onCreate()

The default FileProvider implementation does not need to be initialized.

ParcelFileDescriptor openFile(Uri uri, String mode)

By default, FileProvider automatically returns the ParcelFileDescriptor for a file associated with a content:// Uri.

Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)

Use a content URI returned by getUriForFile() to get information about a file managed by the FileProvider.

int update(Uri uri, ContentValues values, String selection, String[] selectionArgs)

By default, this method throws an UnsupportedOperationException.

Inherited methods

From class android.content.ContentProvider
From class java.lang.Object
From interface android.content.ComponentCallbacks2
From interface android.content.ComponentCallbacks

Public constructors

FileProvider

FileProvider ()

Public methods

attachInfo

void attachInfo (Context context, 
                ProviderInfo info)

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

Parameters
context Context: A Context for the current component.
info ProviderInfo: A ProviderInfo for the new provider.

delete

int delete (Uri uri, 
                String selection, 
                String[] selectionArgs)

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

Parameters
uri Uri: A content URI for a file, as returned by getUriForFile().
selection String: Ignored. Set to null.
selectionArgs String: Ignored. Set to null.
Returns
int 1 if the delete succeeds; otherwise, 0.

getType

String getType (Uri uri)

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

Parameters
uri Uri: A content URI returned by getUriForFile().
Returns
String If the associated file has an extension, the MIME type associated with that extension; otherwise application/octet-stream.

getUriForFile

Uri getUriForFile (Context context, 
                String authority, 
                File file)

Return a content URI for a given File. Specific temporary permissions for the content URI can be set with grantUriPermission(String, Uri, int), or added to an Intent by calling setData() and then setFlags(); in both cases, the applicable flags are FLAG_GRANT_READ_URI_PERMISSION and 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.

Parameters
context Context: A Context for the current component.
authority String: The authority of a FileProvider defined in a <provider> element in your app's manifest.
file File: A File pointing to the filename for which you want a content Uri.
Returns
Uri A content URI for the file.
Throws
IllegalArgumentException When the given File is outside the paths supported by the provider.

insert

Uri insert (Uri uri, 
                ContentValues values)

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

Parameters
uri Uri: The content:// URI of the insertion request. This must not be null.
values ContentValues: A set of column_name/value pairs to add to the database. This must not be null.
Returns
Uri The URI for the newly inserted item.

onCreate

boolean onCreate ()

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.

Returns
boolean true if the provider was successfully loaded, false otherwise

openFile

ParcelFileDescriptor openFile (Uri uri, 
                String mode)

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.

Parameters
uri Uri: A content URI associated with a file, as returned by getUriForFile().
mode String: Access mode for the file. May be "r" for read-only access, "rw" for read and write access, or "rwt" for read and write access that truncates any existing file.
Returns
ParcelFileDescriptor A new ParcelFileDescriptor with which you can access the file.
Throws
FileNotFoundException

query

Cursor query (Uri uri, 
                String[] projection, 
                String selection, 
                String[] selectionArgs, 
                String sortOrder)

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

For more information, see ContentProvider.query().

Parameters
uri Uri: A content URI returned by getUriForFile(Context, String, File).
projection String: The list of columns to put into the Cursor. If null all columns are included.
selection String: Selection criteria to apply. If null then all data that matches the content URI is returned.
selectionArgs String: An array of String, containing arguments to bind to the selection parameter. The query method scans selection from left to right and iterates through selectionArgs, replacing the current "?" character in selection with the value at the current position in selectionArgs. The values are bound to selection as String values.
sortOrder String: A String containing the column name(s) on which to sort the resulting Cursor.
Returns
Cursor A Cursor containing the results of the query.

update

int update (Uri uri, 
                ContentValues values, 
                String selection, 
                String[] selectionArgs)

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

Parameters
uri Uri: The URI to query. This can potentially have a record ID if this is an update request for a specific record.
values ContentValues: A set of column_name/value pairs to update in the database. This must not be null.
selection String: An optional filter to match rows to update.
selectionArgs String
Returns
int the number of rows affected.
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