How do I save and read an integer on android libgdx? - android

How do I save an integer that can be overwritten and then read it on android? I am using libgdx. I know how to do it for my desktop, but I want internal storage.

You should use libgdx Preferences.
That way it will work cross-plattform! (including Android)
Since you just want to store some Integer that should be just what you need.
See example:
//get a preferences instance
Preferences prefs = Gdx.app.getPreferences("My Preferences");
//put some Integer
prefs.putInteger("score", 99);
//persist preferences
prefs.flush();
//get Integer from preferences, 0 is the default value.
prefs.getInteger("score", 0);

There are different ways to do that:
You can write to a FileHandle. Just create a FileHandle like Gdx.files.local("myfile.txt"); and write to it using fileHandle.writeString(Integer.toString(myInt));
Note, that Internal and Classpath are read-only, so you can't write files there.
Also note, that not all types of the gdx.files. are usable for all backends. More on that here.
The second way to do that are the Preferences. The Preferences are the only way to have persistent data for HTML5 applications.
The Preferences are XML files in which you can store, read and change data.
To create Preferences for your app you just need to call:
Preferences myPref = Gdx.app.getPreferences("PreferenceName");
Note, that you should use the full name, for example com.stackoverflow.preferences, as on desktop all Preferences use the same file.
To write data you can use myPref.putInteger("name", value) for Integers, myPref.putBoolean(("name", value) for Booleans... Make sure you call myPref.flush() after all changes, to save the new data.
To get the data you can call myPref.getInteger("name, defaultValue"). The default value is returned if there is no data with the given name.
More on Preferences here.
Hope i could help.

Related

Why does SharedPreferences need two keys?

I'm trying to build a single object that handles all my SharedPreferences, since they are mostly used in the whole app, and I don't quite Understand why it takes two keys to get a value.
The call looks like this:
context.getSharedPreferences(FirstKey, Context.MODE_PRIVATE).getString(SecondKey, default)
I get that its basically built up as a two dimensional array.
The FirstKey gives me a collection of key-value pairs I can use my SecondKey on to get my value. And I get that If I have dozens of SharedPreferences this might come in handy to manage them and prevent mixups/unwanted overwriting.
But is this necessary If I only have like 10 preferences I save anyway or is it reasonable to just use one FirstKey for all of my preferences?
But is this necessary If I only have like 10 preferences I save anyway
or is it reasonable to just use one FirstKey for all of my
preferences?
So for this case you can avoid the use of that FirstKey by using getDefaultSharedPreferences() like this:
SharedPreferences.Editor editor = PreferenceManager.getDefaultSharedPreferences(context).edit();
editor.putString("myKey", "myValue");
editor.apply();
or read already set preferences:
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
String myPref = prefs.getString("myKey", "myDefaultValue");
I guess it is to encapsulate, organize and manage better groups (first key values) of data you want to store (second keys values). So in case you want for example to retrieve all settings preferences you can group them by a Settings file (first key). Or in case you would like to delete all stored values regarding a user preferences (preferred language, preferred currency.. ) then you can organize those data within a "UserPref" file (first key) and then you can iterate within it to either delete all of them when you logout or whatever pogic you see useful for your user experience.
First key
Retrieve and hold the contents of the preferences file
Second key
Retrieve and hold value in this file
You can use only your "FirstKey" for all your preferences and normally dev us it like this only. You can create multiple instances of shared preference by changing the "First key" at the time of getSharedPreference(). Suppose you want two different shared preference for two different modules in your project then change the "FirstKey" parameter, in this case, you have two be careful while storing and fetching data from preference as you have two different shared preference.
As you rightfully stated, the first key represents a group of key-value pairs (which is actually very similar to a single file) and the second key helps you fetch the values in that file/group.
I personally believe this design is great especially in cases where you may want to separate all your values into different categories. If your app is "small", you can save all your values in one single file/group. Otherwise, you can split all your values into separate files/groups.
I hope this helps.. Merry coding!

SharedPreferences - Difference between these two ways of retrieving the Preference value?

I am using the Preference-API..
Typically when I need to retrieve the value of a Preference, I currently do something like this:
final SharedPreferences getPrefs =
PreferenceManager.getDefaultSharedPreferences(getActivity());
boolean isThisPrefEnabled = getPrefs.getBoolean(REFERENCE_TO_PREF_NAME, false);
// OR
String theChosenPref = getPrefs.getString(PREF_NAME, DEFAULT_VALUE);
But I'm curious, couldn't I also do it like this? and if so, what is the difference?
Preference nameOfPref = findPreference(PREFERENCE_KEY);
boolean isPrefEnabled = nameOfPref.isEnabled();
// OR
String thePrefValue = nameOfPref.toString();
It seems to be more efficient, but the first example seems to be what get's used. Why is this?
Thanks.
SharedPreferences is an android specific interface documentation
android.content.SharedPreferences : is a key/value store where you can save a data under certain key. To read the data from the store you have to know the key of the data. This makes reading the data very easy. But as easy as it is to store a small amount of data as difficult it is to store and read large structured data as you need to define key for every single data, furthermore you cannot really search within the data except you have a certain concept for naming the keys.
Preferences is a core java class documentation
java.util.prefs.Preferences : This class allows applications to store
and retrieve user and system preference and configuration data. This
data is stored persistently in an implementation-dependent backing
store.

How to store values in preferences over one another

When i write anything into shared preferences it overwrites the previous value, how can i continuously inject values in preferences and fetch it out all at once like an array? I do not want to use database for this operation.
Thanks
You can use JSON as #CommonsWare points out to store your data in SharedPreferences. I have such an answer that using GSON here:
https://stackoverflow.com/a/5968562/617044
Though not ideal, if you want to use Preferences only, You can store String in preferences. When next value is to be added, retrive the old one add 'comma' and new value.
Whenever you want to use these values, use StringTokeniser. Tokenise elements by 'comma' character.

how to use SharedPreference among activities

I Am writing a code using SharedPreference to store username and password of a user but each time I entered information the older one in xml file are override by newer one what I have to to to get all my data?
SharedPreferences sp1=getSharedPreferences("myshared", 0);
sp1.edit().putString("name", name.getText().toString()).commit();
sp1.edit().putString("pass", pass.getText().toString()).commit();
sp1.edit().putString("age",age.getText().toString()).commit();
sp1.edit().putString("id",id.getText().toString()).commit();
It sounds like you're overwriting your shared preferences between activities. SharedPreferences are persistent like a file on disk, so you shouldn't ever have an issue with the values not being set, hence why you must be overwriting it.
You can get your SharedPreferences by doing
SharedPreferences sp1=getSharedPreferences("myshared", 0);
String name = sp1.getString("name", "noname");
String pass = sp1.getString("pass", "nopass");
...
You can determine if the name/pass was set by checking if they equal the default value (noname and nopass in this case, though it could easily be null).

Best way to retrieve values in android mobile apps

While developing an android app, which is the best and efficient way to retrieve values from the below options:
To get values from a property file or
To get values from app shared preferences.
I like to know this based on memory usage and speed of retrieval.
Edit:
IMO there's no better way as those two options would be used for different purpose.
SharedPreference gives you an easy way to build a user editable Preference page via the PreferenceActivity and to share preference trough your application.
For other purpose as user editable settings you could use Properties files to store data.
For properties you have two good examples here:
http://www.mkyong.com/java/java-properties-file-examples/
http://myossdevblog.blogspot.com/2010/02/reading-properties-files-on-android.html
For SharedPreference see here:
http://developer.android.com/guide/topics/data/data-storage.html#pref
An example:
final SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
final String yourPref = sharedPreferences.getString(getString(R.string.settings_tag_your_pref), "");
or if you don't want to define a tag in string:
final String yourPref = sharedPreferences.getString("your_pref", "");

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