Android 6.0 - external storage files being deleted upon app uninstall

Question

My app uses the DownloadManager to download files to a subdirectory of the device's Music folder.

DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
...
File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC) + "/MyStuff/song.mp3");
request.setDestinationUri(Uri.fromFile(file));

I have noticed that the files are being deleted when the app is uninstalled from a device running Marshmallow (this is not happening on older OS versions). Do you have any ideas about this?

Thanks

Avert

I can reproduce this behavior. I'm not terribly shocked that they did this, but that does feel like a regression. – Uriisa

Note that the same behavior occurs with Android 5.1 (tested on a Nexus 4), but does not with Android 4.1 (tested on a Galaxy Nexus), so the change happened in that range. It's not strictly new to Android 6.0. Based on emulator testing, it looks like the change came in Android 5.0 -- 4.4 keeps the download, 5.0 does not. – Uriisa

Does this only happen for downloaded files, or for all files placed in one of the public folders by an app? If only for downloaded files, then a quick copy would alleviate this, yes? – Ordeal

@Ordeal it's only for downloaded file. But I wonder if it's also done for files put there with addCompletedDownload(). – Rock

@Ordeal it seems to be happening only for downloaded files. I have implemented a file copy as a workaround for this bug: note that the copied file needs to have a different file name, a swap won't work. – Avert

@MatteoInnocenti, thank you. This is good to know. – Ordeal

Any updates on this? – Marguerita

Answer 1

This is done by an internal class called DownloadReceiver and defined in the com.android.providers.downloads package manifest

<receiver android:name=".DownloadReceiver" android:exported="false">
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED" />
        <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
        <action android:name="android.intent.action.UID_REMOVED" />
    </intent-filter>
    <intent-filter>
        <action android:name="android.intent.action.MEDIA_MOUNTED" />
        <data android:scheme="file" />
    </intent-filter>
</receiver>

Here the android.intent.action.UID_REMOVED action catches the eye. It was introduced in Lollipop triggering a call to handleUidRemoved() performing

resolver.delete(ALL_DOWNLOADS_CONTENT_URI, Constants.UID + "=" + uid, null);

Rock

This intent seems to be referring to a user (UID) removed, not an application, (which it would make sense to remove user's downloads after their user is deleted.) developer.android.com/reference/android/content/… – Kinglet

@Kinglet It's not connected to a real user. It refers to Linux system user id assigned to the application. developer.android.com/guide/components/fundamentals.html – Rock

I see. My mistake. – Kinglet

Great find! Nice job. – Minestrone

@Rock Any way to prevent this activity? I'd like the files, downloaded through the app, stay in the external memory of the device even if the app is uninstalled. – Outhaul

@Outhaul I don't know if there's any official fix for this feature. What i've been doing is, downloading the file with another name and change the file name on android.intent.action.DOWNLOAD_COMPLETE bcast receiver. it actually keeps the file but some what sounds like a hack. If you get any other solution, please let me know. – Fountain