Saving Data on Android

disk persistence
 to make your data 
available when you're 
offline
.
• Enabling disk persistence also tracks of 
all the writes you initiated
 while you 
were offline and then when network connection comes back it 
synchronizes
 all 
the write operations.
• Realtime database stores a copy of the data, locally, only for active listeners. You 
can use the 
keepSynced
 method on a database reference to save data locally for 
the location that has no active listeners attached.
• Firebase provides you with the 
real-time presence
 system, which allows your app 
to know the status of your users, are they 
online
 or 
offline
.
• Firebase handles 
latency
 in a way that stores a 
timestamp
, that is generated on 
the server, as data when the client disconnects and lets you use that data to 
reliably know the exact time when the user disconnected.