In Android, will the values in shared preference be retained if the application is killed because of low memory in the device?
To Retaining value of SharedPreferences you have to commit or apply the value.
SharedPreferences.Editor editor = preferences.edit();
editor.putString(ID_ONE, “Value_1”);
editor.putString(ID_TWO, “Value_2”);
editor.putString(ID_THREE, “Value_3”);
editor.apply();
“editor.apply();” is recommended .
Yes that is the purpose of using shared preferences . The storage is persistant
From Official documentation
If you don't need to store a lot of data and it doesn't require structure, you should use SharedPreferences. The SharedPreferences APIs allow you to read and write persistent key-value pairs of primitive data types: booleans, floats, ints, longs, and strings.
The key-value pairs are written to XML files that persist across user sessions, even if your app is killed
link
Yes It does.If you don't like to kill the app or would like to exclude from background under recent apps you can add this code under application tag on AndroidManifest.xml
`android:excludeFromRecents="true"
android:alwaysRetainTaskState="true"`
But add shared preference value to retain the app preference so that the screen state would be same the next time you open the app.
Related
As I know, when a user does "clear data" or "disable" any application, it's shared preferences are cleared and database is also cleared.
So my question is,
Is there any case, that user can perform, in which shared preferences gets cleared but database remains intact ?
Clear data means user wants to clean complete data related to app (sharedpref, cache, db). If you want some data to remain intact even after user tap on "clear data", keep in device storage.
Clear Data will clear everything, Shared Preference, Cache, DB.
If you really want to clear only shared preference (some/all) you can do it programmatically by iterating over Shared Preferences like this:
Map<String, ?> allEntries = prefA.getAll();
for (Map.Entry<String, ?> entry : allEntries.entrySet()) {
Log.i("debug", entry.getKey() + ": " + entry.getValue().toString());
//put delete/edit logic here for some shared preference
}
This logic can be placed based on your app version, or some other logic like when user logs out, but this action would be performed in your app only.
I dont think Android Applications settings allows any option where you can clear only shared preferences and not local db.
You can't save an ArrayList of Objects in Shared Preferences.
From Android Documentation: https://developer.android.com/guide/topics/data/data-storage.html#pref
The SharedPreferences class provides a general framework that allows
you to save and retrieve persistent key-value pairs of primitive
data types. You can use SharedPreferences to save any primitive
data: booleans, floats, ints, longs, and strings. This data will
persist across user sessions (even if your application is killed).
The easiest solution would be to implement serializable in your objects and save them in internal storage.
https://developer.android.com/guide/topics/data/data-storage.html#filesInternal
There is an option to put a database in apk directly. Of course if you use already completed database in your case
Probably a dumb question, but I"m using a SharedPreference with a few different names "MyPrefs1", "MyPrefs2" etc.
I'm assuming this is restricted to my app. i.e. if some other app tries to use the same name, it won't overwrite my values
I pretty much believe my understanding is correct, but the name "SharedPreferences" seem to indicate that it can be shared between apps? (is it for Sharing between activities?)
That's correct, the SharedPreferences are stored in your app's private folder (to be exact, in /data/data/your package name/shared_prefs).
You can give them whatever name you want.
SharedPreferences represent the preferences which can be shared between different components of your application. The SharedPreferences you create in your application is never exposed with other applications.
Whether you use PreferenceManager.getDefaultSharedPreferences() or Context.getSharedPreferences("file_name", Context.MODE_PRIVATE); both are particular to your application only.
Note - SharedPreferences or Preferences is not exposed to other applications.
Although you assumption is right that the SharedPreferences are not shared between apps and thus names cannot clash, it's a good practice (besides of put a specific name to your shared preferences file) to add the package of your application as a prefix. This is useful if you have different flavours and you don't want to overwrite your preferences among them, especially when you're testing an app and don't want to screw up the original values of the shared preferences files.
What is the purpose of SharedPreferences in Android?
Why it is used ?
Where it want to be use?
Shared preferences is used to save any primitive data: booleans, floats, ints, longs, and strings. This data will persist across user sessions (even if your application is killed).
for more visit here
reference earlier answered
You can read the developer android site about SharedPreference to save light data till your application exists into user's device. It will remain saved even after existing your application.
Storage in android with SharedPreference
SharedPreference in android
Hope it will help you..!!!
SharedPreferences is used to permanently store preferences in key:value pair
SharedPreferences is accessible by all the Activity(ies) of an app. Other app cannot directly access the content of shared_prefs
App stores its data/preferences in the SharedPreferences.
E.g. Say in a game u can store ur score, game level, user name, no of kill, etc in the preferences; so that it is accessible all throughout the game; yet by that particular game only.
Game "Gold Miner 2" does it. It is only one example.
Svox tts save ANDROID_ID in preferences file;
You need to keep in mind that if u delete the app, all SharedPreferences will be deleted (/data/data//shared_prefs);
I find the name of stored preferences on Android (SharedPreferences) to be a tad confusing. It was probably chosen with a purpose, so how exactly are these preferences shared? e.g. I don't want other applications accessing my app's information willy-nilly.
What is the difference between preferences from getPreferences() and preferences from getSharedPreferences(), and what is the difference between the different modes? How should I choose which to use? (Heck, if I have a multi-activity program, will using just the regular getPreferences be detrimental?)
My imagination regarding the use of these things is still pretty limited.
It was probably chosen with a purpose, so how exactly are these preferences shared?
They are shared among all components of your application (e.g., all of your activities).
e.g. I don't want other applications accessing my app's information willy-nilly.
SharedPreferences are private to your application by default.
What is the difference between preferences from getPreferences() and preferences from getSharedPreferences(), and what is the difference between the different modes? How should I choose which to use? (Heck, if I have a multi-activity program, will using just the regular getPreferences be detrimental?)
I am not quite certain what you are referring to, since you provided just bare method names with no classes. If you are intending on collecting preference values from the user via the preference screen system, use PreferenceManager.getDefaultSharedPreferences(). I generally use that for everything.
Sharedprefernce are basically key,value pairs with can are saved in an xml and is accessible by an application. You can use it to save some setting value or default values or any other form of key value pairs.
So a key,value pair can be saved in one activity can be accessed in other activity.
Different modes means that whether the data saved can be used by other application or not. You should not worry about all modes. As MODE_WORLD_READABLE & MODE_WORLD_WRITEABLE are deprecated now.
For the difference:-
Difference between getShared/get preference
I have an EditText field called ed. It will store some text that the user will need when the app is started again. I will need to save the text so that when the app is opened again it is back in the EditText field. How do I go about this?
SharedPreference is a way to go.
The SharedPreferences class provides a general framework that allows you to save and retrieve persistent key-value pairs of primitive data types. You can use SharedPreferences to save any primitive data: booleans, floats, ints, longs, and strings. This data will persist across user sessions (even if your application is killed).
Here is the example to implement SharedPreferences.
http://android-er.blogspot.com/2011/01/example-of-using-sharedpreferencesedito.html
or
http://marakana.com/forums/android/examples/63.html
or
One more basic thing you can look up is the example implementation given in the APIDemos of android. APIDemos sample application has all basic examples one need to know.
The most simple way would be to store it as key-value in prefs (putString/getString):
http://developer.android.com/guide/topics/data/data-storage.html#pref