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.
Related
I'm making an Android application and want to create a "Favorites" list for some objects in the app. I wanna make the list accessible and editable in all my activities and I can't really figure out the best way to do this.
Shared preferences? Writing a small txt file to the device? What's the fastest way to do this?
Thanks in advance!
dependencies {
compile 'com.google.code.gson:gson:2.3.1'
}
Then when you want to save, convert your array into String:
ArrayList<Type> yourData = new ArrayList<Type>();
String dataStr = new Gson().toJson(yourData);
//put this dataStr in your shared preferences as String
To retrieve and convert back to an object is also simple:
String str = "";
//you need to retrieve this string from shared preferences.
Type type = new TypeToken<ArrayList<Type>>() { }.getType();
ArrayList<Type> restoreData = new Gson().fromJson(str, type);
If you want to create a Favorites list, use a SQLite Database.
There's really only four ways to store data.
Shared Preferences
Databases
Local files
Remote Server - Slowest since it depends on network connection, so let's skip this.
Between the remaining 3, SharedPreferences is a great option when used to store a single value. However, it's not a good option for storing a Favorites list, mainly because you can only store a single String.
You can still store it by combining all items in your list into one string, then splitting it each time. However, as your Favorites list gets larger, this single long String will too. Splitting and combining all the time isn't efficient.
SharedPreferences is still a decent option if you only have to store the Favorite's list, but since you want to edit it too, it becomes a less attractive solution.
Local Files and Databases are the better options, however local files require you to read in the file each time you want to use it. This process of reading and writing to a file isn't as efficient as using a Database, especially if you want to edit. For example, let's say you want to remove an item from the middle of your Favorite's list. This would require you to read in the file, edit it, then write the change into the file again. Not too pleasant when compared with the ease of the final solution.
Databases are the best option for this, mainly because it's designed to manage data. You can create a single Favorite's table and add each item as it's own individual row. Fetching the entire table becomes quick and easy. Fetching a single item becomes quick and easy. Adding a new item or removing a new item is also quick and easy.
I am building a monopoly game and from what I'm doing I'm almost done, but I want the game to end after 30dice rolls. But the way I want to do it is weird. I need a way to store data and check if the data is upto 30 or not, I mean check the amount of data is a row, I've been looking if sqlite or shared preferences would do, but can't get anything. Any idea would be welcomed and if you can help review my code too, I wouldn't mind. Thank You.
If you realy want to persist it in the Database, you want to have a key-value table current_game_progress with an item dice_rolls and update this each dice roll.
UPDATE current_game_progress SET content = content + 1 WHERE keyname = "dice_rolls"
But its a bit overhead. Maybe you want to store it local in a variable and transfer it on "save" action to the database.
I want to know whether it is possible to save as an array list of double in SharedPreference. In my application, I want the 'size' to be saved whenever there is new 'size' written from the user. It must be uploaded to an array list of double, without erasing the previous one.
first of all - the answer to your question is simple:
it's not possible.
but the good news are that there are lots of ways saving array of doubles (as you've been suggested in the comments):
save it to a binary file / serialized file in the internal/external storage, to SQLite database, make it the responsibility of the server side (if there is one..)
you can save the size of the array in the shared preferences if it helps you read the data from the file containing the serialized array, but I guess you already know that..
anyway - good luck
This is the problem:
I have a form for inputting names, then saves it, then displays it in another activity. But once I try to enter another name, the previous name is overwritten by the new name.
Is there a way to set these names up to list themselves one after another without overwriting each other in SharedPreferences?
You can as long as they have distinct names. Ig you need multiple values for same name, you can store JSON array or use some form of prefix / suffix solution to provide unique names
Either do it like Konstantin Pribluda suggested, or you might think of using the SQLite, if you have a lot of names you want to store (e.g. if creating a history of typed in names). That way you can store unlimited values for the same key and retrieve them as a list/cursor.
But of course that's overkill if you only have 2-3 names…
you can also save a Set of Strings in the SharedPreferences.
I have a listview called history that I call every time that I so something significant (ie open or close the app or record some info) The problem I have is that it records things from top to bottom meaning the most recent information is on the bottom of the listview. The second problem I have is that the listview gets deleted after the app is turned off. How do people usually save their history? (ie shared preferences can only store one variable and thats not enough, I would like to save a maximum of 30 entries to the listview)
Thanks
One option I use is to JSON encode my history list and store the resulting string to SharedPreferences. You can then order it as well (simply add items to the List that backs the ListView with new events first) and save it and restore it from the SharedPreferences file.
EDIT: Try something like this:
org.json.JSONArray tracking_users = new org.json.JSONArray();
tracking_users.put("history 1");
tracking_users.put("history 2");
tracking_users.put("history 3");
You could also consider using a database to store the Log of these events, tends to be more efficient.
See one of these for an introduction to android databases