When is a shared preferences file first created?

Question

I wanted to know when is a shared preference file created for the first time?

I have the following code:

<?xml version="1.0" encoding="utf-8"?>  
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">  
    <PreferenceCategory android:title="User settings">  
        <EditTextPreference android:title="User Name"
        android:key="userName" android:summary="Please Enter User Name"></EditTextPreference>  
        <EditTextPreference android:title="Password"
        android:key="password" android:summary="Password Here"
        android:inputType="textPassword"></EditTextPreference>
</PreferenceCategory>  

</PreferenceScreen>  


  public class PrefsActivity extends PreferenceActivity {  
    /** Called when the activity is first created. */  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        addPreferencesFromResource(R.xml.prefs);  
    }  
}  

Also, how can i use getSharedpreference(), with filename? I don't know if I have to first create this file and place it in app's data directory?

I meant When is a shared preferences file first created: when the application is installed, or some time later? If later, when?

Answer 1

The getSharedPreferences(name, mode) method automatically creates the file with the name specified, so you don't need to create it. Actually, the exact location and name of this preference file is not documented, so I'd suggest you don't rely on some conventions when trying to access this file directly, since the location and name may be changed in future - SharedPreferences should be the only way to access this file.

The preference file with certain name is created when getSharedPreferences(name, mode) or addPreferencesFromResource(preferencesResId) is called for the first time.

Answer 2

I am not 100% sure what you are talking about here.

You don't need to create any files when dealing with PreferenceScreens or SharedPreferences. That is handled by SharedPreferences behind the scenes. I believe that happens when you first set a value in the Preference screen but I honestly am not sure.

SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
String username = preferences.getString("username", "defaultvalue");
String password = preferences.getString("password", "defaultvalue");

That code would get the SharedPreferences for your PreferenceScreen once they have been set. If they haven't been set, you use the default values.