Develop Reference

Does the night mode need sqlite?

I just want to know if the night mode in Android needs sqlite?
or there's another way to save the mode in it
when the user close the app and reopen it again it will save the mode
pls help
If there's another way please share it with me
Thanks

No, sqlite is not needed.
Local application settings such as night mode preference are typically stored in SharedPreferences.

Please, check Shared Preferences. This is key-value storage and it's exactly suited for such needs.
As general practice - create some SharedPrefManager and move all logic with shared preferences there. Like in this answer.

You can just save a variable in the SharedPreferences of the app for the preferred user settings and set theme on launch.
Go through the documentation to know more .SharedPreferences

Write this code on the first page that runs
SharedPreferences pref = getApplicationContext().getSharedPreferences("nightMode", 0);
if(pref.getBoolean("mode",false)){
// code change ui to night
}
and Write this code on the night mode switch
SharedPreferences pref = getApplicationContext().getSharedPreferences("nightMode", 0);
pref.edit().putBoolean("mode",true).apply();
Just as easily

Android SharedPreferences: How to define keys at runtime?

The Android documentation describes how to create a "preferences" UI using either a PreferenceActivity or a PreferenceFragment. The preferences themselves are defined in a XML file (e.g. preferences.xml) which contain, among other things, the "key" (android:key) to use to store each preference in the app's SharedPreferences.
This is good for apps which have a single set of preferences. However let's assume that there is an app that can have multiple "items" (for example: multiple account in a video chat app), and needs to show a preferences screen for each account.
How can this be done? Is it possible to specify the keys at runtime (so that e.g a different prefix can be used for each account)? Is there a better way to approach this?

Yes, its possible!
you can assign keys on Runtime like, but as you said in comments that you need to change the Keys of the pre-defined Preferences in Xml rather than creating new Preferences explicitly, here's a method -
Preference pref = findPreference("my_pref");
String myPrefix = "prefix_";
pref.setKey(myPrefix + pref.getKey());

Migrate from getSharedPreferences(custom file) to getDefaultSharedPreferences()

When I originally wrote and published my app, I was using a custom written activity to handle application settings. I used custom file name to store shared preferfences, like this:
getSharedPreferences("custom_settings_file",MODE_PRIVATE);
But now I'm refactoring my app and I would like to implement PreferenceActivity or PreferenceFragment and an xml file with PreferenceScreen section. Every tutorial or example that I've seen is using
getDefaultSharedPreferences(context);
to retrieve shared preferences, because PreferenceActivity assumes default filename to store preferences and there's no way to tell it to use a different one(at least I couldn't find one after an hour of searching and reading documentation).
So now I have a problem. If I just simply use the new default file, existing users of my app will lose their settings when they update the app, because the new application will not know anything about "custom_settings_file". What would be the best way to move the data from an old file to a new one on app update?
Here are the possible options that I could come up with:
Extend Application class and implement a piece of code in onCreate() so that every time my app is launched, it would check for existence of "custom_settings_file" and move it's contents to the new one. But running a block of code on every app launch seems like wasting too much processing resources for an operation that only needs to run once.
Just notify the user that their old settings are gone. But obviously this is not acceptable.
Is there a better solution, than option 1? Perhaps someone has already faced a similar problem?

What is preventing you from doing number 1 only once?
Just add a "migration" boolean to the new sharedpreferences.

If you also load the xml preference file then you can try this:
PreferenceManager.setDefaultValues(context, YOUR_PREFERENCE_NAME, MODE_PRIVATE, R.xml.preference_file, false);
If not (you want to add each preference item dynamically in your code) then you can do like this:
PreferenceManager pm = getPreferenceManager();
pm.setSharedPreferencesMode(MODE_PRIVATE);
pm.setSharedPreferencesName(YOUR_PREFERENCE_NAME);
In case you still want to use the defaultSharedPreference and process the migration then ... I'm writing this and I see Nicklas's answer, so I'm done here.

Could you add value in your new SharedPreferences that records whether you are a new install or an upgrade. If you don't have the setting in your sharedpreferences, check to see if you have an old preferences file in the way you were before. Then convert those preferences to your new method, and set your private setting indicating that it's been upgraded. Then just set the new value indicating the new state and you won't need to check your old preferences any more.

How to bind the automatic preferences file to the custom preferences in android

I just implemented a preferences screen for one of the sample apps that I am creating. I followed the guide given on google site. All is fine and I loaded up a ListPreference and I am able to store it and persist it also. There is also one minor problem here. I have already defined a custom preference file for the app but this automatic handling of the preference screeen seems to be creating a preference file on its own. For now I was trying to get this code to work but it is not getting the custom preference file.
final Preference customPrefs = getPreferenceScreen().findPreference(Utils.PREFS_NAME);
customPrefs.setOnPreferenceClickListener(new OnPreferenceClickListener() {
public boolean onPreferenceClick(Preference preference) {
customPrefs.getEditor().commit();
return true;
}
});
Is there a way to bind the custom preference file with this auto preference class in anyway ?

You can set a custom name for the file used to store the preferences, used in your PreferenceActivity, by calling its getPreferenceManager().setSharedPreferencesName("file_name") method. Just remember that you need to set that before calling addPreferencesFromResource, otherwise your UI will still change stuff back to the wrong file (the default one).
As I said, you don't need to do that, since you can use the default file provided by the system. If/when you need to read the preferences elsewhere, you can then just call PreferenceManager.getDefaultSharedPreferences(Context context).
I already addressed those remarks in another question.
Also remember that some of the methods are deprecated. If you're writing new code, try to avoid them and conform to the new "Fragment Way" of doing things.

Dynamic preferences for a variable number of profiles in an Android app

I am looking for a way to create dynamic preferences where I don't need to hard code the preference key and I could have a variable number of preferences.
Basically, my application will let the user create a multiple number of profiles and each of these profiles will save custom values for a fixed number of preferences.
So this way, the user does not have to change the preferences every time he wants this app to run differently, he can just switch the profile.
One way I think will work is by subclassing all the standard Preference classes and calling their setKey method with my custom preference key, containing the profile name, but this is ugly.
So is there a cleaner and more standards compliant way to do this?
Regards,
Dhruwat

You can save different preferences in a different file for each user using the getSharedPreferences method:
getSharedPreferences() - Use this if you need multiple preferences files identified by name, which you specify with the first parameter.
That way, you can do something like this:
SharedPreferences settings = getSharedPreferences("prefs_user_"+user_id, 0);
// from now on you can use use the normal way to set or get the preferences
I'm assuming you are using an id in order to identify them users.