I have some scens with and I want save their state of view when app is closed. Some times it's one thing like "is that scene has opened shop window?" but sometimes ther is much more info which I need to store. So is better to use for it UserDefaults/SharedPreferences (json to string) or create model, serialize those info to model then save it to DB?
I will be thankful for Your opinion.
I use SharedPreferences when i have to save a variable, such as UserName, Country of Origin, access token, location, UsersCurrentLevel, UsersCurrentHealth etc.
I use Database when i have data that requires much manipulation or has more specifications to it. Such as questions for users,
video ad's details(seenState , directoryPath, urlToDownloadVideo, hasVideoBeenAlreadyDownloaded etc.), lists of data, etc.
So i would suggest you use a mix depending on the data.if it has a single entry use SharedPreference else if it has a list/ multiple data for a single format put it in a DB. Hope this helps.
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 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.
I'm using a RecyclerView as a checklist that can be used as a grocery list for example, first the user adds the product(item), the price and the store, then my app adds this item object into my ArrayList adapter; each item in my adapter is a relative layout with 3 TextViews for the product, price and store. The problem occurs when the user shuts down his device or closes the app: the RecyclerView resets to nothing.
What is the easiest way to save items in a RecyclerView so that it stays? Do I save in the cache?
Shared Preferences
or
SQLite Databases
You will need to save the data to persistent storage in some way. For something small, it would be best to use SharedPreferences. Then, when you re-open the app, load the data from SharedPreferences into your ArrayList, then populate the RecyclerView.
To use SharedPreferences you will need to convert your data into a String, because SharedPreferences can only handle primitive data types. The best way to convert lots of data to a String is by converting the data into a JSONObject, then that JSONObject into a String (which can be stored in SharedPreferences).
JSON is like a dictionary, it's a way to store Key-Value pairs. See this SO question for more information and some examples of what it looks like. Then search for how to use JSON and Android (or reference the docs).
EDIT: If your RecyclerView is showing a simple amount of data, you may be able to store a Set<String> in your SharedPreferences. See this relevant documentation.
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 am trying to develop a user input form where i take his details and store them
in the form i have fields for his name, email, address, phone number etc.
a person may have multiple emails or multiple phone numbers.
he can add a field by clicking a button.
and then i want to store the data entered by the user in a shared preference.
i have a question:
how do i retrieve data from dynamically added extra fields by the user?
I have maintained a count for dynamically added fields for each field criteria (like email, phone etc)
but i am stuck at the point where i am supposed to retrieve the data when i need to store them in Shared Preferences.
Please help! thankyou in advance.
Is it possible using something like ParentViewGroup.getChildCount() or something else?
Sure, you can use getChildCount() and getChildAt() methods to retrieve child from a ViewGroup.
However, I think the better way is to save the references to the Views you added when you add them into the View hierarchy, and get data from these references.