Develop Reference

Questions about retrieving/refreshing data using Volley (and SimpleXML) on Android

All the data my Android app displays is taken from a XML file. I'm using Volley to retrieve the data and SimpleXML to map the XML data to objects using a Volley custom Request: SimpleXmlRequest.
Every time I refresh the content, it reads the whole XML file and creates every single object again and I have the feeling that this is not the best way to do it, cause this file can be quite large. So I have a few questions about that:
Is there a way to "subscribe" to the XML file to retrieve only the
new items added on it, avoiding to read the whole file every time? I know Volley can cache but doesn't help so much here.
Would it be possible to make a SimpleXmlArrayRequest using
SimpleXML framework? Would it help? Cause I really don't want to
parse the file by myself...
If not, would it worth to switch from XML to Json so I could use
JsonArrayRequest or would I have to read the whole file and refresh
every single item anyway? I've never used it before.
Many items from the source file are displayed as a list using
RecyclerView but, again, when I refresh, I have to remove the items
it had before and add them all again as I'm getting all the items at
once and consequently can't use
RecyclerView.notifyDataSetChanged().
I've been reading a lot, even until finding out the RxJava and RxAndroid which seems perfect but it looks like too hard to integrate Volley and SimpleXML on it... so I hope you can help me :)
Thanks!

I always work with Json apart from being very light, with libraries like GSON its fun to work with.
To get only new new data, my practice is to include two fields in the database tables, 1 for isDeleted (boolean) and 1 for lastModified (long epoc time).
The isDeleted field applies only if the data is accessed by multiple users.

How to get data from ActiveAndroid to support ListView virtualization

As far as I know, Android listview shows the data virtualized (meaning it loads only the visible ones), so it is fast as it can be.
I have lots of data to get from the database (around 2000 but with lots of data in the fields), and I use ActiveAndroid in an AsyncTask to get them.
Unfortunately the AsyncTask with AA takes around 10-15 seconds to get the data so I see a progressbar during that time.
I get his by this code:
LocalDateTime start=new LocalDateTime();
LogCat("Start: "+start);
elements = new Select().from(Data.class)
.where("Data_Id=?", DataId).orderBy("Name ASC").execute();
LogCat("Elements: "+elements .size());
LocalDateTime end=new LocalDateTime();
LogCat("End: "+end);
LogCat("Time: "+(new Period(start,end).getSeconds()+" s"));
It would be good to accelerate the loading by somehow virtualizing the data retrieval.
I also use a search in the listview, that searches the whole list. So considering the would be also good.
What do you suggest? How should I proceed?

Pairing content provider and CursorLoader should solve your issue.

What is the best way to use threading on a sorting algorithm, that when completed, creates a new activity and gives its data to the new activity?

I will start this by saying that on iOS this algorithm takes, on average, <2 seconds to complete and given a simpler, more specific input that is the same between how I test it on iOS vs. Android it takes 0.09 seconds and 2.5 seconds respectively, and the Android version simply quits on me, no idea if that would be significantly longer. (The test data gives the sorting algorithm a relatively simple task)
More specifically, I have a HashMap (Using an NSMutableDictionary on iOS) that maps a unique key(Its a string of only integers called its course. For example: "12345") used to get specific sections under a course title. The hash map knows what course a specific section falls under because each section has a value "Course". Once they are retrieved these section objects are compared, to see if they can fit into a schedule together based on user input and their "timeBegin", "timeEnd", and "days" values.
For Example: If I asked for schedules with only the Course ABC1234(There are 50 different time slots or "sections" under that course title) and DEF5678(50 sections) it will iterate through the Hashmap to find every section that falls under those two courses. Then it will sort them into schedules of two classes each(one ABC1234 and one DEF5678) If no two courses have a conflict then a total of 2500(50*50) schedules are possible.
These "schedules" (Stored in ArrayLists since the number of user inputs varies from 1-8 and possible number of results varies from 1-100,000. The group of all schedules is a double ArrayList that looks like this ArrayList>. On iOS I use NSMutableArray) are then fed into the intent that is the next Activity. This Activity (Fragment techincally?) will be a pager that allows the user to scroll through the different combinations.
I copied the method of search and sort exactly as it is in iOS(This may not be the right thing to do since the languages and data structures may be fundamentally different) and it works correctly with small output but when it gets too large it can't handle it.
So is multithreading the answer? Should I use something other than a HashMap? Something other than ArrayLists? I only assume multithreading because the errors indicate that too much is being done on the main thread. I've also read that there is a limit to the size of data passed using Intents but I have no idea.
If I was unclear on anything feel free to ask for clarification. Also, I've been doing Android for ~2 weeks so I may completely off track but hopefully not, this is a fully functional and complete app in the iTunes Store already so I don't think I'm that far off. Thanks!

1) I think you should go with AsynTask of Android .The way it handle the View into `UI
threadandBackground threadfor operations (Like Sorting` ) is sufficient enough to help
you to get the Data Processed into Background thread And on Processing you can get the
Content on UI Thread.
Follow This ShorHand Example for This:
Example to Use Asyntask
2) Example(How to Proceed):
a) define your view into onPreExecute()
b) Do your Background Operation into doInBackground()
c) Get the Result into onPostExceute() and call the content for New Activty
Hope this could help...

I think it's better for you to use TreeMap instead of HashMap, which sorts data automatically everytime you mutate it. Therefore you won't have to sort your data before start another activity, you just pass it and that's all.
Also for using it you have to implement Comparable interface in your class which represents value of Map.
You can also read about TreeMap class there:
http://docs.oracle.com/javase/7/docs/api/java/util/TreeMap.html

How to present parsed JSON in readable format to users?

So I have JSON, I parsed in and it's sitting there. From my code below it looks like I have put everything into an ArrayList but then what? I mean for example I need the "title" of each JSON object to be an onClick on the first page, is that possible?
Essentially my onPostExceute() is empty/not doing much. Eventually I need to separate each object into it's own page via the onlicks I'm mentioning, but I think I can do that by separating the JSONObjects...? guess I'll come to that when I can.
If I want to separate things should I even be using an ArrayList? It's just what I used for a server test I ran with different code.
Would really appreciate some help. Basically stuck at the last hurdle is how I perceive it. Maybe I'm wrong though. The logs see that the JSON is showing up as one big chunk.
Edit: Removed my code, this is more of a theory question. ListView being the best thing to go with.

yes you can make spearate arraylist for them..and can store them in diferent listviews...on google click you can open new listview showing id and link for google ..and same you can do for microsoft and your other trem.And using onItemClick is a gud option,you can easily get the index of item clicked//

Trying to pull API into LinearLayout Android APP

I am a beginner of Android apps and am using Eclipse. I have found some larger samples of pulling APIs but I cannot find a simple one to get started with. I simply want to pull from an XML file on the web (by using an API KEY) and throw it in a LinearLayout (Vertical). I can then go from there, anyone know of any? Below is a sample of my XML:
<xmldata>
<Products>
<ProductCode>ITI-GR12</ProductCode>
<ProductName>Granada 9-3/4" Narrow Rim Platter</ProductName>
<ProductPrice>64.4000</ProductPrice>
</Products>
</xmldata>

I am assuming you are looking for mechanisms which help you to parse XML and extract data from it...Voila here is a link to get you started with different ways of doing it...
http://www.ibm.com/developerworks/opensource/library/x-android/
Good luck!

your question is not easy as you will have quite a lot of programming to achieve what you want.
Here are the steps :
read your data using sax
fill a data structure of your own (build a
class, data members will be filled by
previous parsing)
build an activity, use a layout you define to
show all UI fields you think you need
to display your data
fill the content of each view using the data
structure you filled on step 2.
If you are a beginner, I suggest you first understand steps 3 and 4, having fun with UIs, then try to understand how you could download your file, parse it and fill some data class to provide content for the views.
Regards,
Stéphane