Develop Reference

Android ArrayAdapter equivalent in Gtk?

Displaying an array of objects in a GtkTreeView can be quite complicated, as you have to copy the values from the array into a GtkListStore and then write a lot of code to keep them synchronized. (Or store the objects in the ListStore directly, which is then clumsy to access)
Android has an elegant solution to this issue by having an Adapter class, which is a wrapper for an array where all you have to define is a function that gets the nth item of the array and fills a widget or row with it. (Along with methods for handling the nth row being clicked, etc.)
Does a similar class exist in Gtk? (or a 3rd party addition)
How would one go about implementing a class like this?

There is no such a class in Gtk. If you want to implement it, you will need to rewrite (or subclass) GtkListStore (source), or to be more precise, write a new class which realizes GtkTreeModel interface. Plus you should somehow notify your model when the array changes.

How to transfare data from DB to some buiseness entity

Now I am working on Android application which has one main Activity that is displaying some data via GLSurface. This data can be changed in many ways. For this I have several fragments with some lists of variants with extra logic. Problem is that I need somehow transfer data from one place to another.
For example:
I have fragment with list of elements. I used RecyclerView with custom adapter. I am filling list with data from DB. SomeThingDBEntity for example. When I am getting it from Room DB (using Room entities), but it has some extra fields that only required for showing elements in RecyclerView. I need to send user's choice from adapter to fragment, then from fragment to activity, than activity sends it to some class that incapsulates logic of work with GLSurface. SomeThingGLentity for example. Now I am passing only fields, that requered by SomeThingGLentity for showing data (int, String etc.), but in future this list can grow. I can also send directly SomeThingDBEntity and get required fields only in the end when apply changes to SomeThingGLentity. But is it OK to use Room DB entity this way?
Is there any better way of doing this? I can also create third class which will only contain required fields. But where to place and how to call it? Maybe there are some patterns or guidelines of best way of doing it...

It looks like you need a data mapper. Something similar to this - https://github.com/android10/Android-CleanArchitecture/blob/master/data/src/main/java/com/fernandocejas/android10/sample/data/entity/mapper/UserEntityDataMapper.java.
If you use this approach, you will be able to encapsulate the transformation logic from your DBEntity to your BusinessEntity, and if you will change the data format in one of them, only your mapper will need to be edited.

"global" array with different data types - Android

I'm new in programming for Android so maybe my question will be very easy to solve but still. I'm trying to make an array of different data types :
I have to add there :
int number
String name
int number_2
int time
int total
And my question now is how to implement it in easiest way, and how to get data from it. In case that I have to get a different records for this variables and store it into list .
Also have a question about way how to keep all values which I handle inside of my array.
I have to keep it because in my program I have to go back to other activities go forward to another and again collect data and add it to my array.
What will be the best and easiest solution ?
Thanks in advance for help

You could create the Array as an Array of Objects. All other classes are derived from Object, so you'll be able to store all types of objects in your Array. However, you would have to check the type of an object you get from the Array, before you'd be able to safely interpret as an object of a specific class. Moreover, you would have to use Integer instead of int.
If all (or at least multiple) of your elements you are intending to store in the Array are belonging to one (physical) entity, you could create a custom Class that holds its own properties as class members, and fill your Array with a list of instances of this Class.
Moreover, if you plan to add elements to your Array, you should use a List instead, e.g. an ArrayList.
As for retaining your data, you would have to either store it in a database, or save it to a file. In either way, you will have to save it upon close of the Activity, and load it again once the Activity starts

To pass the data across activities you will need to pass them using objects you can store in an intent. Seems like the best way to handle that is to either create a PREFS file to store the data or to create an object that extends Parcelable like here:
https://stackoverflow.com/questions/18593619/android-parcelable-object-passing-to-another-activity
Parcelables are preferable assuming you need all the data in a single object, you do not want to "putExtra" a bunch of fields and you also want to be sure data can pass from one activity to another. Otherwise, a simple Util class that reads and writes to a PREFS file is the way to go:
android read/write user preferences
A database is always another option, but seems well outside the scope of your question.

Using multiple static ArrayLists through a whole Android application

I am developing my first android Application and hoping to get some tips here.
I am getting a JSONObject from an url which then will be parsed in an ArrayList<MyObject>. The list will be used in multiple tabs and be filtered as needed for the tabs. The objects within these list can be modified by the user and the changes should be synchronized with the lists.
So, to speed up loading time I have created a class DataHolder as a singleton which contains 7 arraylist, based from the one JSONObject in different sorting order and filter criterion. The objects in these lists are references from the original list. Populating the lists works fine.
The lists will be used in different fragments and activities.
Now the problem: the second activity contains tabs with fragments. After initializing the fragment... all arraylists in the DataHolder counts 0! I have to save the JSONObject in SharedPreferences and populate it again to get the List. I can't load the url again because it is slowing down the app to much and using SharedPreferences is not an option (I think) because of the need to synchronized the Lists. I have read that using static variables is not the optimal solution, but it seems to be the easiest way :(
What can I do to solve this problem? Should I use Parcelable Objects and always pass the Lists around? Or maybe use SQLite? Or are there other approaches?

The SQLite way is definitively the correct approach, imho.
You should use the internal database to store such lists :
http://developer.android.com/guide/topics/data/data-storage.html#db

use static list for local operation .when user comes out of that screen(activity) save that changes into database.

Controlled Iteration through XML Data

Good afternoon,
I have a simplistic app (just learning) that reads some xml data from a mocked up file. The XML data is well formed into 6 categories and I use the SAX parser to read it. My app basically has two buttons prev & next. So when the app loads I'd like to see the first category of xml data. When the user presses next button...well then I'd like to see the next category of data etc. to the end. My question is how do I go back and forth through the data? Do I load it all into a data object with some form of sorting and iterate back and forth throught the object or do I add an atty field to a parent element and just search the xml for the requested atty and child data? I don't forsee the xml ever getting very large. Just trying to get more experienced input into how to go about synchronizing the data with the gui.
TIA
JB

There are many ways you could go about it. One that is generally a decent path is parse the XML into a data structure that can be used by an Adapter to create the view structures and return them so be shown. That will give you a good level of control over how your data looks and allow you to tie in to many different complex View structures pretty easily.
The data structure that you store it in also has many possibilities. Which ones work best would depend on your particular dataset generally.
Given what I know about your data an ArrayList seems like a straightforward approach. Create yourself a class that will hold all of the data about one category. Create objects of that class in your parser as you are pulling the data out of the XML file, each time you get to a new category add your object to an ArrayList. When your done you should have an List structure that has 1 category object(with all of its data) at each index.
Once you've got that set up make yourself an ArrayAdapter with your List. Override the getView() method to inflate your View objects and populate them with the data from your List.
This Adapter can then feed a parent View (ViewPager, ViewSwitcher, ListView etc...) These parent views will make it easy to iterate over your data structures (i.e. switching from one category to the next and back.)