Develop Reference

How to store a small list, on Android? SharedPreferences VS SQLite VS file

I have an app that generates objects of a class, let's call it X, that is Serializable. I want the user to be able to occasionally save or delete objects of X from his/her list of favorites (a list that can go up to 100 objects).
What is the most appropriate way to persistently store the list of favorites?
In SharedPreferences, storing the whole list as a JSON String
In an SQLite database:-
Storing one item per object, as BLOB's
Storing one item per object, as JSON Strings
In a custom file, storing the whole list as a JSON String
Some other way?
My thoughts are:
Because adding and removing favorites will be occasional, and the list is small, I probably don't need the advantages of a DB when it comes to searching fields in large amounts of data. So I am inclined to maintain a local ArrayList, add and remove items from it, and save it to SharedPreferences (option 1).
It seems odd to save a key-value pair holding an entire list as a JSON String, I'm afraid I might be unaware of some sort of limitation.
Is there a limit to the size of the String I can store in SharedPrefferences?
Is it too problematic that I add or remove objects from my local ArrayList and then save the whole list?

I am agree with your first approach because of It's manage easily and need small storage space.

String Array in SharedPreferences

I need to work with a persistent String Array (n Rows, 1 column).
* On first running the app, the String Array needs to be created empty.
* On subsequent app executions the Array will be populated from a File and the contents need to be available throughout the rest of the app.
* As the app is executed, the Array needs to be able to 'grow' in row count
* As the app is executed, the Array rows need to be able to grow in length
* The user will have the option to Clear the Array of previous entries.
* At the end, the String Array contents will be written back to a File.
I find a lot of references to Putting and Getting from an existing SharedPreferences String[] but, in the newness of my Android development, I am struggling with how to proceed.
EDIT Follows...
The data itself suggests using an Array
Example:
MAIN ST. F55 63 KY08:57 12142015--------KY11:24 12142015345TMH KY13:57 12142015
MAIN ST. F56 WYE123 IN08:57 12142015--------KY11:24 12142015--------KY13:57 12142015
1ST ST. F57 --------KY08:57 12142015--------KY11:24 12142015789FPF KY13:57 12142015
1ST ST. F58 456FPF KY08:57 12142015998FPF KY11:24 12142015--------KY13:57 12142015
1ST ST. F59 789TTM KY08:57 12142015--------KY11:24 121420151234DG KY13:57 12142015
I first need to have this data in a File
Then in one GUI I check for the existence of the file.
If one exists, fine
If none exists, I create one.
Then, in subsequent GUI's, I must check for the existence of parameters
If they do not already exist, add them to the existing data lines.
If they already exist, notify the user
And so on and on.
Then when all of the current 'pass' data has been collected via multiple, separate GUI's, I have to write out the whole data-set into the file.
My reason for thinking that I need a SharedPreference approach is the need to find and check data from GUI to GUI as the user progresses through the app.
If that 'belief' is wrong, I am open to better approach suggestions.
EDIT 2 follows....
On further study of web references, I am beginning to think that perhaps the best approach for this data and how the data needs to change might be to use a SQLite approach. Any ideas about this?
Any assistance/suggestions you might have would be greatly appreciated.

i would discourage you from using sharedpreferences for anything else than preferences. means things that change rarely - really rarely and are really lightweight. do not put much data in there. less is better. the data structures underlying sharedpreferences are not a database.
another note. it is not a string list, but it would be a string set. sets are not necessarily ordered, nor do they necessarily keep their order. means - it is not rows. its a collection of strings that can come back in any fun order (usually there is some, but that depends on the implementation which i do not know)
now you could go and make your own list, your own data structure, save it into a string and read it out, use json to do exactly that or something similar, or better - use a database, which would exactly do that.
http://developer.android.com/training/basics/data-storage/databases.html
explains it, but as you'll see its something that might take some time.
now dont get me wrong, but i have to warn you about the following approach. it is valid, but has many problems and is far from thread safe. it will not be a problem as long as you only open it from the ui thread and do not keep anything in memory to cache - if you do it will create lots of problems.
your problem of adding a line and clearing can be solved by using a file. just a simple file
look here
http://developer.android.com/training/basics/data-storage/files.html#WriteInternalStorage
the change is to append when writing:
openFileOutput("filename", Context.MODE_APPEND);
see the context mode? now you can basically just write one line and append every time.
if you wanna clear the file, just deleteFile("filename")
this is as said not threadsafe, but can be a viable option if used carefully.

Please follow this step to achieve what you want with sharedPreference
create the class Parent for SharePreference
Create your empty Array
Convert Your empty array to String and put it on SharedPreference
to call your empty array from sharedPreference
Call your sharedPreference using your key
Convert the String to array
You get your array from the sharePreference
Hope it helps, and maybe this link will help you :
http://www.androidhive.info/2012/08/android-session-management-using-shared-preferences/

You can use my open-source library called prefser, which solves this problem and uses SharedPreferences and Gson under the hood. It's basically wrapper for default Android mechanism.
You can use it in the following way:
Prefser prefser = new Prefser(context); // create Prefser object
prefser.put("key", Arrays.asList("one", "two", "three")); // save array of Strings
String[] value = prefser.get("key", String[].class, new String[]{}); // read array of Strings
For more information check repository of the project, tests and README.md file.
Link: https://github.com/pwittchen/prefser
Please note, SharedPreferences have some limitations and shouldn't be used for storing large amount of data. If you expect a lot of data, consider using SQLite database or another type of database (e.g. with NoSQL or similar approach if you strive for simplicity).

OK, based on the data, how it needs to be manipulated and the pros and cons of using a SharedPreferences approach, I have decided to go with a SQLite approach.
With that approach I should be able to readily check:
* if the necessary table exists (if not create it)
* if the necessary Field1 + Field2 exists (if not create a new record)
* and I will be able to modify the record's Field3 contents as needed
Then when the user's actions are complete I can convert the SQLite table 'records' into strings and write them out as a File and then either DROP or PURGE the associated SQLite table (until needed next time).
I sincerely appreciate all of your suggestions.
Thank you.

Android 3 linked values

What would be the best way to store multiple 3 linked values (String, String, Boolean)? Like in a HashMap for example.
I need to:
save them in SharedPreferences
load them of sp (of course)
change at least the last value dynamically
get all items where the last value is true (for example)

You have three options:
Store it on preferences
Store it in a database
Save a file on disk
If you want to proceed with preferences I will suggest you to convert the 3 value format to a Json format and store it in preferences as json.
{"value1":"value", "value2":"value", "value3":"value"}
or
{"data":"some data",
"link":{
"data":"other linked data",
"link":{...}
}
}
This kind of data is also stored perfectly in a noSQL database. But if you do not want to add a database at all to your project, maybe you can have a look to some noSQL libraries like SimpleNoSQL (it indeed uses a database behind the scenes, but abstracts you very well from it) or Realm (it stores on disk).

Adding elements and saving that elements to array that is created in strings.xml

Suppose Type is the name of the array which contains A,B,C,D as elements and is created in strings.xml.Now in the form user can either select any of the elements or add new elements.Suppose user adds E,F,G .Now what i want to achieve is that anyhow the Type array have A,B,C,D,E,F,G in it. Using sqlite is done.But i want to save it in the Type array only and not anywhere else.Is it possible ?

Since anything that you define in res folder acquires a unique id in R.java, which is an array, and size of array cannot be changed at runtime.. So, it is not possible.

You can only save data to persistent storage like SQLite data base, shared preferences or a text file, each of which have different strengths and weaknesses and are suited for different situations, so take your pick.

Maximum Size of SharedPreferences class

I want to save a lot of strings with SharedPreferences class .
These strings are quit long.
I really want to know the maximum length of a string that can be save in shared preferences in android.And Also How much size of data i can store in This SharedPrefernces class.

As per android architecture there is no such limit to store data in SharedPreference. Better way is to database (SQLite) when you have to deal with huge amount of data

I read somewhere that there is no hard limit other than Integer.MAX_VALUE ( maximal string length). But it is not advisable to store that much on shared preferences, as this is XML file which must be parsed and you will have a problems while parsing it.
I used to store about 50-100KBytes there. It worked.

The exact answer obtained manually is: maximum Unicode symbol's size is 5657632 symbols (or from [0 to 5657631]) in my case. It's some about 2.7MB for SharedPReference.Editor .
Rather large storage.
You ca use this size twice:
PreferenceManager.getDefaultSharedPreferences(c)
context.getSharedPreferences("<key>", <Mode>);

Of course is't limit for SharedPreferences but if system won't have enough memory it is one first stuff what DELETE it, you remember it.