使用FileProvider在Android用户之间共享文件

Question

I am looking to share a file with a service running with the android:singleUser attribute. The file is saved into the local data directory for the Android User. So this could be something like one of the follow:

• /data/user/0/com.example.fileshare/files/myfile.txt
• /data/user/10/com.example.fileshare/files/myfile.txt
• /data/user/11/com.example.fileshare/files/myfile.txt

I start the service to share this file like:

Uri fileUri = FileProvider.getUriForFile(getApplicationContext(), "com.example.fileshare.fileprovider", file);

Log.d(TAG, "Share File URI: " + fileUri.toString());

Intent shareFileIntent = new Intent(getApplicationContext(), FileSharingService.class);
shareFileIntent.setAction(Intent.ACTION_SEND);
shareFileIntent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
String mimeType = getContentResolver().getType(fileUri);
Log.d(TAG, "Share File MIME Type: " + mimeType);
shareFileIntent.setDataAndType(
     fileUri,
     mimeType);

startService(shareFileIntent);

But when I receive the intent that was sent from any user of than the UserHandle.USER_OWNER in my FileSharingService The ContentResolver cannot find the file because the file does not exists in the same users data directory that the service is running in because of the android:singleUser attribute.

@Override
protected void onHandleIntent(Intent intent) {
    Log.d(TAG, "onHandleIntent - " + intent.getAction());

    if (Intent.ACTION_SEND.equals(intent.getAction())) {
        Uri fileUri = intent.getData();

        // When I try and read the file it says that the file does not exist. 
        FileInputStream in = getContentResolver().openInputStream(fileUri);
    }
}

Here are the FileProvider and Service in the AndroidManifest.xml:

<provider
    android:name="android.support.v4.content.FileProvider"
    android:authorities="com.example.fileshare.fileprovider"
    android:grantUriPermissions="true" >
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/file_paths" />
</provider>

<service
    android:name="com.example.fileshare.FileSharingService"
    android:exported="true"
    android:singleUser="true" >
    <intent-filter>
        <action android:name="android.intent.action.SEND" />

        <category android:name="android.intent.category.DEFAULT" />

        <data android:mimeType="*/*" />
    </intent-filter>
</service>

Answer 1

I ended up using a DocumentsProvider with the android:singleUser="true" and android:exported="true" instead of FileProvider.

With a subclass of DocumentsProvider set up I could then use this piece of code to create a new document and write the contents of the file from the one user into the resolved Uri returned.

final ContentResolver resolver = getContentResolver();
Uri derivedUri = DocumentsContract.buildDocumentUri(
                        "com.example.documentsprovider.authority", "root");
client = acquireUnstableProviderOrThrow(
                        resolver, "com.example.documentsprovider.authority");
childUri = DocumentsContract.createDocument(
                        client, derivedUri, mimeType, displayName);


InputStream in = mContext.getContentResolver().openInputStream(myFileUri);
OutputStream os = mContext.getContentResolver().openOutputStream(childUri);

byte[] buf = new byte[1024];
int len;
while ((len = in.read(buf)) > 0) {
    os.write(buf, 0, len);
}

in.close();
os.close();