Saving Data on Android

Saving the user preferences
First, you have to create some constants which will represent the keys for the key—
value pairs of data you need to save. Open 
NotePrefs.kt
 and insert the following 
declarations right below the declaration of 
DEFAULT_PRIORITY_FILTER
:
  
private
 const 
val
 KEY_NOTE_SORT_PREFERENCE = 
"note_sort_preference"
 
  
private
 const 
val
 KEY_NOTE_PRIORITY_SET = 
"note_priority_set"
Next, you have to create the function to write the sort order to the prefs file.  Insert 
the code below into 
saveNoteSortOrder()
, replacing the 
TODO
:
sharedPrefs.edit() 
    .putString(KEY_NOTE_SORT_PREFERENCE, noteSortOrder.name) 
    .apply()
This code retrieves the 
Editor
 object from the app's prefs and puts the sort order in 
the preferences as a 
String
 with the key 
KEY_NOTE_SORT_PREFERENCE
. It then uses 
apply()
 so that the changes will be written asynchronously to the disk.
Now, provide the code to write the selected priority filters. Insert the code below into 
saveNotePriorityFilters()
, once again replacing the 
TODO
:
sharedPrefs.edit() 
    .putStringSet(KEY_NOTE_PRIORITY_SET, priorities) 
    .apply()
Saving Data on Android
Chapter 2: Shared Preferences
raywenderlich.com
44

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The previous code puts 
priorities
, a 
Set
 of 
String
s, representing the selected 
priority filters, into the prefs using 
putStringSet()
 with the key 
NOTE_PRIORITY_SET
.
Awesome! The functions to write to the prefs are done. Next, you'll add the code to 
read the values.