FileProvider

public class FileProvider
extends ContentProvider

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

<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().

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

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="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);

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 FLAG_GRANT_READ_URI_PERMISSION, 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 FLAG_GRANT_READ_URI_PERMISSION or 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 Activity is active. When the stack finishes, the permissions are automatically removed. Permissions granted to one 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 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 int TRIM_MEMORY_BACKGROUND int TRIM_MEMORY_COMPLETE int TRIM_MEMORY_MODERATE int TRIM_MEMORY_RUNNING_CRITICAL int TRIM_MEMORY_RUNNING_LOW int TRIM_MEMORY_RUNNING_MODERATE int TRIM_MEMORY_UI_HIDDEN

Inherited methods
From class android.content.ContentProvider ContentProviderResult[] applyBatch(ArrayList<ContentProviderOperation> arg0) void attachInfo(Context arg0, ProviderInfo arg1) int bulkInsert(Uri arg0, ContentValues[] arg1) Bundle call(String arg0, String arg1, Bundle arg2) Uri canonicalize(Uri arg0) abstract int delete(Uri arg0, String arg1, String[] arg2) void dump(FileDescriptor arg0, PrintWriter arg1, String[] arg2) final String getCallingPackage() final Context getContext() final PathPermission[] getPathPermissions() final String getReadPermission() String[] getStreamTypes(Uri arg0, String arg1) abstract String getType(Uri arg0) final String getWritePermission() abstract Uri insert(Uri arg0, ContentValues arg1) boolean isTemporary() void onConfigurationChanged(Configuration arg0) abstract boolean onCreate() void onLowMemory() void onTrimMemory(int arg0) AssetFileDescriptor openAssetFile(Uri arg0, String arg1, CancellationSignal arg2) AssetFileDescriptor openAssetFile(Uri arg0, String arg1) ParcelFileDescriptor openFile(Uri arg0, String arg1, CancellationSignal arg2) ParcelFileDescriptor openFile(Uri arg0, String arg1) final ParcelFileDescriptor openFileHelper(Uri arg0, String arg1) <T> ParcelFileDescriptor openPipeHelper(Uri arg0, String arg1, Bundle arg2, T arg3, PipeDataWriter<T> arg4) AssetFileDescriptor openTypedAssetFile(Uri arg0, String arg1, Bundle arg2) AssetFileDescriptor openTypedAssetFile(Uri arg0, String arg1, Bundle arg2, CancellationSignal arg3) Cursor query(Uri arg0, String[] arg1, Bundle arg2, CancellationSignal arg3) Cursor query(Uri arg0, String[] arg1, String arg2, String[] arg3, String arg4, CancellationSignal arg5) abstract Cursor query(Uri arg0, String[] arg1, String arg2, String[] arg3, String arg4) boolean refresh(Uri arg0, Bundle arg1, CancellationSignal arg2) final void setPathPermissions(PathPermission[] arg0) final void setReadPermission(String arg0) final void setWritePermission(String arg0) void shutdown() Uri uncanonicalize(Uri arg0) abstract int update(Uri arg0, ContentValues arg1, String arg2, String[] arg3)
From class java.lang.Object Object clone() boolean equals(Object arg0) void finalize() final Class<?> getClass() int hashCode() final void notify() final void notifyAll() String toString() final void wait(long arg0, int arg1) final void wait(long arg0) final void wait()
From interface android.content.ComponentCallbacks2 abstract void onTrimMemory(int arg0)
From interface android.content.ComponentCallbacks abstract void onConfigurationChanged(Configuration arg0) abstract void onLowMemory()

Public constructors

FileProvider ()

Public methods

void attachInfo (Context context, 
                ProviderInfo info)

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

String getType (Uri uri)

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

Uri insert (Uri uri, 
                ContentValues values)

boolean onCreate ()

ParcelFileDescriptor openFile (Uri uri, 
                String mode)

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

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