This lesson teaches you to
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To securely offer a file from your app to another app, you need to configure your app to offer
a secure handle to the file, in the form of a content URI. The Android
FileProvider
component generates content URIs for
files, based on specifications you provide in XML. This lesson shows you how to add the default
implementation of FileProvider
to your app, and how to
specify the files you want to offer to other apps.
Note: The FileProvider
class is part of the
v4 Support Library. For information
about including this library in your application, see
Support Library Setup.
Specify the FileProvider
Defining a FileProvider
for your app requires an entry in
your manifest. This entry specifies the authority to use in generating content URIs, as well as
the name of an XML file that specifies the directories your app can share.
The following snippet shows you how to add to your manifest the
<provider>
element that specifies the
FileProvider
class, the authority, and the
XML file name:
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.myapp"> <application ...> <provider android:name="android.support.v4.content.FileProvider" android:authorities="com.example.myapp.fileprovider" android:grantUriPermissions="true" android:exported="false"> <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/filepaths" /> </provider> ... </application> </manifest>
In this example, the android:authorities
attribute specifies the URI authority
that you want to use for content URIs generated by the
FileProvider
.
In the example, the authority is com.example.myapp.fileprovider
. For your own
app, specify an authority consisting of the app's
android:package
value with the string "fileprovider" appended to it. To learn more
about the authority value, see the topic
Content URIs and the documentation for the
android:authorities
attribute.
The <meta-data>
child element of the
<provider>
points to an XML file that specifies the directories you want to
share. The android:resource
attribute is the path and name of the file, without
the .xml
extension.The contents of this file are described in the next section.
Specify Sharable Directories
Once you have added the FileProvider
to your app manifest,
you need to specify the directories that contain the files you want to share. To specify the
directories, start by creating the file filepaths.xml
in the res/xml/
subdirectory of your project. In this file, specify the directories by adding an XML element for
each directory. The following snippet shows you an example of the contents of
res/xml/filepaths.xml
. The snippet also demonstrates how to share a subdirectory
of the files/
directory in your internal storage area:
<paths> <files-path path="images/" name="myimages" /> </paths>
In this example, the <files-path>
tag shares directories within the
files/
directory of your app's internal storage. The path
attribute
shares the images/
subdirectory of files/
. The name
attribute tells the FileProvider
to add the path segment
myimages
to content URIs for files in the files/images/
subdirectory.
The <paths>
element can have multiple children, each specifying a different
directory to share. In addition to the <files-path>
element, you can
use the <external-path>
element to share directories in external storage, and
the <cache-path>
element to share directories in your internal cache
directory. To learn more about the child elements that specify shared directories, see the
FileProvider
reference documentation.
Note: The XML file is the only way you can specify the directories you want to share; you can't programmatically add a directory.
You now have a complete specification of a FileProvider
that generates content URIs for files in the files/
directory of your app's
internal storage or for files in subdirectories of files/
. When your app generates
a content URI for a file, it contains the authority specified in the
<provider>
element (com.example.myapp.fileprovider
),
the path myimages/
, and the name of the file.
For example, if you define a FileProvider
according to the
snippets in this lesson, and you request a content URI for the file
default_image.jpg
, FileProvider
returns the
following URI:
content://com.example.myapp.fileprovider/myimages/default_image.jpg