Develop Reference

Saving Shared Prefrences in Multiple instances

I would like to be able to save my users session or sharedPrefrences in a way that if the user kills the application and you start it it would look like this.
Button one = Start Activity with Blank Preferences
Button Two = List of Saved Sessions of Preferences and once clicked all put into the Starting activity.
Is this possible and if so how would I go about doing that?
Thank you!

Yes you can do that and it is good to use sharedPreferences if you just have to store some session variables. But if it is more, then go for database.
Do clear sharedPrefences in your application you need to do this:
SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(activity);
Editor editor = settings.edit();
editor.clear();
editor.commit();
For reading the preferences, you can keep a sharedPreference with the count for the seesions. While saveing the prefences, always save with the strings session1, session2, session3 etc. So, while accessing them based on count, prepare a loop and form the string and access all the session variables and show them.
The reason why I didnt suggest you to do getAll() for sharedPreference is that, you may save few other things in sharedPreference. So by forming strings yourself, while reading you can just get the sessions and not other data saved in sharedPreference.
I hope you understand what I meant

Is this possible
I would say yes, depending on exactly what you mean.
if so how would I go about doing that?
SharedPreferences has a couple different functions to do something like this, depending on exactly what you want. You can get a Map of all preferences that are stored after clicking Button2 with getAll() or a set of preferences with a certain String such as "userName" or something similar with getStringSet(). Play around with the functions it offers and see if it gives you what you are looking for.
Also take not of the warnings of these functions
Note that you must not modify the set instance returned by this call. The consistency of the stored data is not guaranteed if you do, nor is your ability to modify the instance at all.

How can I save the state of the checkboxes in a custom listview using sharedpreferences?

I have checkboxes in my custom listview, I'm using a boolean array to save the state of these checkboxes. I want to make the state of checkboxes persistent through out the lifetime of the app.I know that this can be achieved through sharedpreferences, but I don't exactly know how this can be done.

I know that this can be achieved through sharedpreferences, but I don't exactly know how this can be done.
There is no option to push serializable objects into sharedpreferences. Because of that, you'll be forced to convert the boolean array to one of the supported types. The only one I can see making sense would be to convert the state of the array into a string like :
"0|1|0|1|1"
Then push that into the shared preferences. To do this you could use the Arrays.toString(boolean []). You will, however, have to write a parse method for extracting the value back out from the SharedPreferences. That is probably the easiest option to accomplish this.

How to attach a Preference to a particular SharedPreferences?

I am working on implementing the preferences for our application. I know how to display preferences UI and how to read/write values using SharedPreferences. In our app, I need to handle two sets of preferences and I would like to ask about this issue, one comment in the Android documents in particular.
The documentation for Preference.getSharedPreferences() has the following comment under the Return values section:
Returns The SharedPreferences where this Preference reads its value(s), or null if it isn't attached to a Preference hierarchy.
I would like to ask how it is possible to attach a SharedPreferences to a particular Preference, be it EditTextPreference or others. In other words, how does the persistence code in a Preference know that it should store the user input in one particular SharedPreferences object and not the other?
To explain my question further with an example, suppose I have the following:
SharedPreferences prefs1 = getSharedPreferences(file1, mode);
SharedPreferences prefs2 = getSharedPreferences(file2, mode);
My question is what API I should use so that prefs1 is used by the Preference objects' persistence code and not prefs2.
The target is Nexus One, running 2.3.4.
Maybe the answer is obvious but I could not find it after reading the documentation and searching the web. Thank you in advance for your help.

In other words, how does the persistence code in a Preference know that it should store the user input in one particular SharedPreferences object and not the other?
Preference uses PreferenceManager's getSharedPreferences(), which eventually routes to getDefaultSharedPreferences().
You are welcome to create your own Preference subclasses that change this behavior, but since the preference screen system may not be designed to handle multiple SharedPreference objects, there's a chance that your preference changes might not get persisted.
IOW, I encourage you to reconsider:
In our app, I need to handle two sets of preferences

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.

How to save preferences to somewhere other than SharedPreferences

My application is used on multiple platforms so it saves it preferences to a file (rather than to the standard Android SharedPreferences).
Is there any easy of reusing the PreferenceActivity to save preferences to a file or is it a case of creating a whole new activity to do the job? If the latter is the case is there a layout I can use that will make the activity look like the normal preferences screen? PreferenceActivity uses com.android.internal.R.layout.preference_list_content but this doesn't appear to be available to apps for reuse.

Is there any easy of reusing the
PreferenceActivity to save preferences
to a file or is it a case of creating
a whole new activity to do the job?
Not really. I mean, you could subclass SharedPreferences, rip the guts out, and map it to your own data model, but that would be far, far worse for maintainability than just using SharedPreferences in the first place.
If the latter is the case is there a
layout I can use that will make the
activity look like the normal
preferences screen?
It's just a ListView. It will take you a lot more time to do this than to just use SharedPreferences.
PreferenceActivity uses
com.android.internal.R.layout.preference_list_content
but this doesn't appear to be
available to apps for reuse.
Sure it is. If you have the SDK installed, it's on your hard drive right now. Look in $ANDROID_HOME/platforms/$API/data/res/layout, where $ANDROID_HOME is where you have the SDK and $API is some API (e.g., android-2.1).

You can create a function that exports the data from SharedPreferences to a file.

Normally Preferences are saved into sharedpreferences when the user clicks on the prefrence item. Add your code to update your external dataholder on onPreferenceTreeClick() function.