Android Google drive App data folder return empty when I use queryChildren
We have identified an issue with the API that meant App Folder content was not downloaded after an app was uninstalled then reinstalled. This will be fixed in the next release of Google Play services.
For development purposes, you can work around this issue in the current Google Play services (version 6.1) by clearing Google Play services data (Settings > Apps > Google Play services > Manage Space > Clear all data). We don't recommend suggesting this solution to end users as this will likely clear data relied on by other apps.
Regards,
Daniel