Preferences

Preference works as data persistence. We have other choices to save data in Android.
One is creating setting file, the other is using database(SQLite3).
Compare to other choices, preference is easy to use.

Preference

Preference is key-value store. These data may be written under file.
We need to manage only key, value. :)

How to

SharedPreferences spf = PreferenceManager.getDefaultSharedPreferences(this);
		
// Read 
boolean key = spf.getBoolean("key", false);
				
// Write
spf.edit().putBoolean("key", true).commit();

In this case, the argument of getDefaultSharedPreferences is Activity(Context)
commit is same as database commit.(save immediately)

Key-Value Type

There are several key-value type of preference
Float, Int, Long, String, Set

Type Get Set
float getFloat(String key, float defValue) putFloat(String key, float value)
int getInt(String key, int defValue) putInt(String key, int value)
long getLong(String key, long defValue) putLong(String key, long value)
boolean getBoolean(String key, boolean defValue) putBoolean(String key, boolean value)
String getString(String key, String defValue) putString(String key, String value)
Set<String> getStringSet(String key, Set<String> defValue) putStringSet(String key, Set<String>)

See get method, all method has default value, if you are missing to set value, you can get this value.

Ref

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