Depends, If you only want to save sessions of user use SharedPrefrence or else if the data is more you can use sqlite
/**
* method to set the login status for the application
*
* @param context
* @param status
*/
public static void setLoginStatus(Context context, int status) {
sharedPreferences = context.getSharedPreferences(PREFERENCE_NAME, Activity.MODE_PRIVATE);
Editor editor = sharedPreferences.edit();
editor.putInt(KEY_LOGIN_STATUS, status);
editor.apply();
}
NOTE :
About that its totally on your choice what you use to save the current
state of user , i will prefer using shared preferences. And for signup
and sign in use SQLite database. Shared preferences are commonly used
to perform light operations. You can search through data in SQLite as
you may have many users.
So use SQLite to register and login and then use shared preferences to
save tha current state of user.