I've written a simple app which modifies KitKat devices to allow user-installed applications to write to the MicroSD card on devices with two storage locations.
Background information on the underlying problem is available here: https://plus.google.com/+TodLiebeck/posts/gjnmuaDM8sn Please ensure you understand the problem and that your device has it before installing this app. This app is quite useless if your device doesn't suffer this issue.
[[[[ THIS IS A BETA RELEASE. WHILE I HAVE TESTED THIS ON MULTIPLE DEVICES MANY TIMES, PLEASE RESTRICT YOUR USE OF THIS APP TO DEVICES YOU HAVE THE ABILITY TO REFLASH FROM SCRATCH. I do not expect this to occur, but this is release #1 of this app, and it modifies a configuration file as root. That said, my test devices still work even when I deliberately corrupted and deleted the target file in testing. ]]]]
This app is entirely free. It doesn't have any ads, (but it does have a few Play Store links on its final screen to my other free apps).
It will be going on the Play Store pending your feedback, but I wanted to post it here first. Please let me know if you encounter any issues.
How it works: The /system/etc/permissions/platform.xml is modified to specify that all applications which have the WRITE_EXTERNAL_STORAGE permission are registered as members of the Android UNIX group "media_rw". Membership in this group is necessary to write to the MicroSD card.
In Android 4.3, most all devices granted access to the media_rw group to apps. In Android 4.4, they do not. This app simply restores the old behavior. From what I've observed this method (granting permission via platform.xml), also appears to be the preferred means of restoring SD card access on XDA and elsewhere.
This app is designed to abort if it sees absolutely anything that it does not expect. Please let me know if the app does not work for you, and what type of device/ROM/etc you're using. If the modification is unnecessary (due to media_rw access being already present) this app will make no modification.
The original platform.xml will be backed up in /system/etc/permissions as "platform.xml.original-pre-sdfix" (unless that file already exists).
- Play Store: https://play.google.com/store/apps/d...=nextapp.sdfix
- Direct download: http://android.nextapp.com/sdfix/r7/SDFix_r7.apk
The installed app is named "NextApp SDFix".