问题
My app is setup to allow backups to be saved to a Google Drive appdata folder. It all works perfectly well on the same device. When I make a backup, delete the app's data, then restore it all works.
However, when I try to backup on one device, then install on another and attempt to restore there are no files found. Same goes for when I uninstall the app on the original device, reinstall it on the same device and attempt to restore. Both cases result in no files being found despite the fact that I see there are files in the appdata folder when I log into Google Drive.
I read somewhere that you must use the RESOURCE_ID instead of the DRIVE_ID of a file for it to work between devices since a DRIVE_ID will be different from device to device. However the only way I've seen how to get the RESOURCE_ID is by using the driveId.getResourceId(), and I can't get the proper DRIVE_ID from another device.
tl;dr: how should I go about retrieving the proper file from the appdata folder that was created by another device/installation?
回答1:
I have a database backup option in my app as well. I implemented it using the new Google Drive Android Api and what's more important, it works perfectly fine from one device to another.
Here's how I did it and what I recommend:
- Before reading or writing anything to Google Drive, call requestSync to make sure everything is synchronized and up to date (see how to use it here).
- Retrieve your files by name using a query instead of identifiers. As Google Drive allows multiple files with the same name, order your query by date and use the newest one.
- To avoid creating multiple backup files with the same name, use a query to find if the backup file already exists on Google Drive and if it does, open it and overwrite it.
- This is the point I guess you won't like: I recommend not using the Appfolder... for the moment. Google has acknowleged there might be some synchronization issues with it when uninstalling and reinstalling the app. I tried to use the Appfolder as well in my app without success and I finally ended up creating an ordinary folder in Google Drive. With that said, you can try the first three recommendations before adopting this one.
I hope these points can help with your implementation. If you need anything else, just tell.
来源：https://stackoverflow.com/questions/27899129/android-access-google-drive-appdata-folder-from-another-device-but-same-app