Saving Data on Android

SharedPreferences
, or 
prefs
 for short, API provides the means to read and 
write to a file that is formatted as 
XML
. The API is especially useful when you need 
to store things like application-wide flags to style your app, user progress, data 
filters and so on.
The prefs file you create, edit and can delete is stored in the 
data/data/{application 
package name}
 directory. The location of this file can be obtained programmatically 
by calling 
Environment.getDataDirectory()
. Like files, the data is app—specific 
and will be lost if the application data is cleared through settings or if the app is 
uninstalled.
You already learned that 
SharedPreferences
 should not be used to store large 
amounts of data, but rather small features of your app. As such, the data is 
structured into 
key—value
 pairs, where each value has an identifier key, which 
marks its location in the file. Then, by passing in the key, you can retrieve the last 
value you stored. If there is no value for the key, you can specify a default that will be 
returned instead. Furthermore, since the point of 
SharedPreferences
 is to store 
simple data, the only supported types to store are 
Int
, 
Float
, 
Long
, 
String
 and 
Set
.
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