Handling full disk storage in Android
The way I handle this is with error handling around all file operations so that the app won't just crash, and I do a file stat (https://stackoverflow.com/a/5083482/1317564) on the directory being used by the user to ensure there's enough free space. If not, I show them a nice big error message. ;) Generally the phone itself will do plenty of complaining as well, so they should notice the problem sooner or later.
This is the error, "phone storage is full! Delete some files to free space." I have at least 7 gigs of free space.Your phone's internal memory is full. Not your memory card. They are entirely seperate.
Try uninstalling some apps that you don't need anymore. And also try clearing cache on some of your apps.