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• I'm having a hard time wrapping my head around handling the Activity Lifecycle...

  - by kefs

  So it seems i've created a fatal flaw and coded an app before understanding/handling rotation/lifecycle events.. Currently, all of my code is in onCreate of each activity. I've read a lot of lifecycle tutorials online, including the official dev guide info, but i'm still having an almost unbelievably hard time trying to wrap my head around the rotation/lifecycle events/methods and when to use them correctly. For example, my app currently has an activity that opens the db, inserts a record, then closes the db.. if i rotate my screen on this activity, the data is re-entered into the db. Using the available lifecycle events (onPause(), onResume(), etc..), how would I prevent this db call from happening again? Would I have to pass a variable through the state saying that the db call has been done, and not to do it again? Thanks in advance..

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• class method as hash value

  - by demas

  I have this working code: class Server def handle(&block) @block = block end def do @block.call end end class Client def initialize @server = Server.new @server.handle { action } end def action puts "some" end def call_server @server.do end end client = Client.new client.call_server My Server will handle more then one action so I want to change code such way: class Server def handle(options) @block = options[:on_filter] end def do @block.call end end class Client def initialize @server = Server.new my_hash = { :on_filter => action } @server.handle(my_hash) end def action puts "some" end def call_server @server.do end end client = Client.new client.call_server It is incorrect code because action() method calls on create my_hash, but if I try to modify code to: my_hash = { :on_filter => { action } } i get error message. Is it possible to create hash with methods as hash values ?

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• Does anyone else think instance variables are problematic in database-backed applications?

  - by Ben Aston

  It occurs to me that state control in languages like C# is not well supported. By this, I mean, it is left upto the programmer to manage the state of in-memory objects. A common use-case is that instance variables in the domain-model are copies of information residing in persistent storage (i.e. the database). Clearly this violates the single point of authority principle, and "synchronisation" has to be managed by the developer. I envisage a system where instead of instance variables, we have simple public access/mutator methods marked with attributes that link them to the database, and where reads and writes are mediated by a framework that decides whether to hit the database. Does such a system exist? Am I completely missing the point, or is there some truth to this idea?

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• What are the other new features of C# 4.0, after dynamic and optional parameters?

  - by Abel

  So, C# 4.0 came out yesterday. It introduced the much-debated dynamic keyword, named and optional parameters. Smaller improvements were the implicit ref and recognizing of indexed and default properties on COM methods, contra- and co-variance (really a .NET CLR feature, not C# only) and... Is that really it? Are dynamic and optional/named params the only real improvements to C#? Or did I miss something? Not that I'm complaining, but it seems a bit meager after C# 2.0 (generics) and C# 3.0 (lambda, LINQ). Maybe the language just reached actual maturity?

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• Fastest/One-liner way to list attr_accessors in Ruby?

  - by viatropos

  What's the shortest, one-liner way to list all methods defined with attr_accessor? I would like to make it so, if I have a class MyBaseClass, anything that extends that, I can get the attr_accessor's defined in the subclasses. Something like this: class MyBaseClass < Hash def attributes # ?? end end class SubClass < MyBaseClass attr_accessor :id, :title, :body end puts SubClass.new.attributes.inspect #=> [id, title, body] What about to display just the attr_reader and attr_writer definitions?

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• C# Asynchronous Sockets questions.

  - by ccppjava

  Based on my reading and testing, with asynchronous sockets, the socket itself can be passed using state object (IAsyncResult result), also if store the socket as a private field, it would be captured by the callback methods. I am wondering how the IAysnResult is kepted between the BeginXXX and ReceiveXXX? It looks to me that after the BeginXXX call and the method ends, the state object would be disposed by GC if there is no reference to it. In the case of private field, how the private field is shared between threads? (As far as I know, a callback is executed using a thread from the default thread pool, which would be considered as a new thread.) Many thanks, hope the questions themselves are clear.

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• Which would be better? Storing/access data in a local text file, or in a database?

  - by TerranRich

  Basically, I'm still working on a puzzle-related website (micro-site really), and I'm making a tool that lets you input a word pattern (e.g. "r??n") and get all the matching words (in this case: rain, rein, ruin, etc.). Should I store the words in local text files (such as words5.txt, which would have a return-delimited list of 5-letter words), or in a database (such as the table Words5, which would again store 5-letter words)? I'm looking at the problem in terms of data retrieval speeds and CPU server load. I could definitely try it both ways and record the times taken for several runs with both methods, but I'd rather hear it from people who might have had experience with this. Which method is generally better overall?

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• ArrayBlockingQueue exceeds given capacity

  - by Wojciech Reszelewski

  I've written program solving bounded producer & consumer problem. While constructing ArrayBlockingQueue I defined capacity 100. I'm using methods take and put inside threads. And I've noticed that sometimes I see put 102 times with any take's between them. Why does it happen? Producer run method: public void run() { Object e = new Object(); while(true) { try { queue.put(e); } catch (InterruptedException w) { System.out.println("Oj, nie wyszlo, nie bij"); } System.out.println("Element added"); } } Consumer run method: public void run() { while(true) { try { queue.take(); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("Element removed"); } } Part of uniq -c on file with output: 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 2 Element removed 2 Element added 102 Element removed 102 Element added

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• Fragment savedInstanceState is always null (Android support lib)

  - by Evgeny Egorov

  I wrote a simple test project, but I cant understand why I always receive savedInstanceState = null in lifecycle methods onCreate, onCreateView and onActivityCreated. I change the screen orientation, see the log, but state not saved. Tell me please where is my mistake. Thanks. The code of fragment class is: public class TestFragment extends Fragment { private String state = "1"; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { if (savedInstanceState != null) { //never works state = savedInstanceState.getString("state"); } //always prints 1 Toast.makeText(getActivity(), state, Toast.LENGTH_SHORT).show(); return inflater.inflate(R.layout.fragment_layout, container, false); } @Override public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putString("state", "2"); Log.e("", "saved 2"); } }

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• Giving proper credit to a projects contributors

  - by Greg B

  I've recently been working with an opensource library for a commercial product. The opensource code is distributed from the website of the company who sells the proprietary product as a zip file. The library is a (direct) port to C# of the original library which is in Java. As such, it uses methods instead of getter/setter properties. The code contains copyright notices to the supplier of the product. The C# port was originally provided to the company by a 3rd party individual. I have modified the source to be more C# like and added a couple of small features. I want to put my version of the code out there (Google code or where ever) so that C# users of the software can benefit from a more native feeling library. How can I and/or how should I amend the copyright notice to give proper credit to The comercial owner of the original source The guy who provided the original C# port Myself and anyone else who contributes to the project in the future The source is provided under the LGPL V2.1,

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• memory usage in iOS

  - by varun

  My app has a simple UI interface having simple buttons, date picker, picker view, table view, action sheet, toolbar, alert boxes etc. No images, no network access. Just plain simple UI. It accesses SQLite database a lot. ARC option is enabled. I have many questions to ask: In .h files, I am defining IBOutlets like @property(nonatomic, retain) IBOutlet UIButton *bt; Where do i need to do bt=nil? in didReceiveMemoryWarning or viewDidLoad Live Bytes in Instruments tool is 4-5MB. Is it enough or I need to reduce memory usage? If so, how can I do so? Please mention few important points. Also, what all need to be added to the following methods? applicationDidReceiveMemoryWarning UIApplicationDidReceiveMemoryWarningNotification

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• Qt: any way to automatically generate QSharedData-based structures?

  - by Eye of Hell

  Hello. Qt has a build-in supprt for creating objects with integrated reference counting via QSharedData and QSharedDataPointer. All wordks great, but for each such object i need to write a lot of code: QSharedData-based implementation class with constructor and copy constructor, object class itsef with accessor methods for each filed. For a simple structures with 5-10 fields this requires really lot of near same code. Is it some ways to automate such classes generation? Maybe it's some generators exists that take a short description and automatically generates implementation class and object class with all accessors?

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• Best approach to creating a database driven Java website?

  - by Craig Whitley

  I'm fairly new to programming and new to java, but I'd like to jump in the deep end with a little database driven website project. I've read quite a lot about requirements in the 'real world' requesting experience with Spring and Hibernate, so I have those installed on netbeans and a project created (if I hit run I get the default spring page). Now I just need a little guidance as to where to start designing my app (please tell me if I'm getting in a bit too over my head for a beginner!). Should I start off with my classes? - create all my classes as they map to my database tables and decide which attributes and methods each will require? Can anyone suggest any good books for maybe.. making a java based website from scratch (i.e. from design right through to deployment) that might be useful for a beginner? Any help appreciated thanks.

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• Basic QT Event handling / Threading questions ?

  - by umanga

  Greetings , I am new to QT (4.6) and have some basic questions regarding its event mechanism.I come from Swing background so I am trying to compare it with QT. 1) Does Event-processing-loop run in seperate thread? (like EventDispatch thread in Swing) ? 2) If we open several 'QMainWindow' do they run in several threads? 3) Whats the best way to run an intensive process in a seperate thread? (like SwingWorker in Swing ? ) 4) If intesive-process runs in a seperate thread ,is it possible to call UI methods like update(),repaint() from that process? thanks in advance.

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• Using scanf() in C++ programs is faster than using cin ?

  - by zeroDivisible

  Hello, I don't know if this is true, but when I was reading FAQ on one of the problem providing sites, I found something, that poke my attention: Check your input/output methods. In C++, using cin and cout is too slow. Use these, and you will guarantee not being able to solve any problem with a decent amount of input or output. Use printf and scanf instead. Can someone please clarify this? Is really using scanf() in C++ programs faster than using cin something ? If yes, that is it a good practice to use it in C++ programs? I thought that it was C specific, though I am just learning C++...

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• How can an SQL query return data from multiple tables

  - by Fluffeh

  I would like to know how to get data from multiple tables in my database, what types of methods are there to do this, what are joins and unions and how are they different from one another? When should I use each one compared to the others? I am planning to use this in my (for example - PHP) application, but don't want to run multiple queries against the database, what options do I have to get data from multiple tables in a single query? Note: I am writing this as I would like to be able to link to a well written guide on the numerous questions that I constantly come across in the PHP queue, so I can link to this for further detail when I post an answer. The answers cover off the following: Part 1 - Joins and Unions Part 2 - Subqueries Part 3 - Tricks and Efficient Code

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• Microsoft learning support for VS2010

  - by John

  OK, I am a big fan of WPF, and while it is large area to fully understand, Microsoft has been great in posting loads of training video at http://windowsclient.net/learn/videos_wpf.aspx However with the release of 2010 it all seams to have gone very quiet. I expected a lot of the support to be updated for 2010 and I also expected a lot of new videos on the best way to use the new features in 2010. Currently I find myself working through videos based on 2008 (or even 2005) and trying to apply them to 2010. Don't get me wrong it not that I mind doing this, it just that I fear I may be learning methods which have better or different solutions in 2010. It is just me expecting too much of Microsoft, or have I missed out on a new website?

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• How to Audit Database Activity without Performance and Scalability Issues?

  - by GotoError

  I have a need to do auditing all database activity regardless of whether it came from application or someone issuing some sql via other means. So the auditing must be done at the database level. The database in question is Oracle. I looked at doing it via Triggers and also via something called Fine Grained Auditing that Oracle provides. In both cases, we turned on auditing on specific tables and specific columns. However, we found that Performance really sucks when we use either of these methods. Since auditing is an absolute must due to regulations placed around data privacy, I am wondering what is best way to do this without significant performance degradations. If someone has Oracle specific experience with this, it will be helpful but if not just general practices around database activity auditing will be okay as well.

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• Serializing System.Drawing.Color in .NET

  - by alankdkd

  Hi all, I've used the default .NET serialization for a class with a System.Drawing.Color member. The code is now in use by people, and I need to add an extra member to the class, but still deserialize older versions. So I tried the standard way of doing this: The ISerializable interface, using SerializationInfo methods to get the int and string members. The problem: My class also has a System.Drawing.Color member, but SerializationInfo doesn't provide a "GetColor" method read this data type. I've tried getting it as an int and as a string, and casting it to System.Drawing.Color, but no luck. Does anyone know how to deserialize a System.Drawing.Color from SerializationInfo? Thanx! Alan

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• C++ Multiple Inheritance Question

  - by John

  The scenario generating this is quite complex so I'll strip out a few pieces and give an accurate representation of the classes involved. /* This is inherited using SI by many classes, as normal */ class IBase { virtual string toString()=0; }; /* Base2 can't inherit IBase due to other methods on IBase which aren't appropriate */ class Base2 { string toString() { ... } }; /* a special class, is this valid? */ class Class1 : public IBase, public Base2 { }; So, is this valid? Will there be conflicts on the toString? Or can Class1 use Base2::toString to satisfy IBase? Like I say there are lots of other things not shown, so suggestions for major design changes on this example are probably not that helpful... though any general suggestions/advice are welcome.

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• Tracing all events in VB.NET

  - by MatsT

  I keep running into situations where I don't know what event I have to listen to in order to execute my code at the correct time. Is there any way to get a log of all events that is raised? Any way to filter that log based on what object raised the event? EDIT: Final solution: Private Sub WireAllEvents(ByVal obj As Object) Dim parameterTypes() As Type = {GetType(System.Object), GetType(System.EventArgs)} Dim Events = obj.GetType().GetEvents() For Each ev In Events Dim handler As New DynamicMethod("", Nothing, parameterTypes, GetType(main)) Dim ilgen As ILGenerator = handler.GetILGenerator() ilgen.EmitWriteLine("Event Name: " + ev.Name) ilgen.Emit(OpCodes.Ret) ev.AddEventHandler(obj, handler.CreateDelegate(ev.EventHandlerType)) Next End Sub And yes, I know this is not a good solution when you actually want to do real stuff that triggers off the events. There are good reasons for the 1 method - 1 event approach, but this is still useful when trying to figure out which of the methods you want to add your handlers to.

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• What is an Enterprise Java Bean really?

  - by HDave

  On the Tomcat FAQ it says: "Tomcat is not an EJB server. Tomcat is not a full J2EE server." But if I: use Spring to supply an application context annotate my entities with JPA annotations (and use Hibernate as a JPA provider) configure C3P0 as a connection pooling data source annotate my service methods with @Transactional (and use Atomikos as JTA provider) Use JAXB for marshalling and unmarshalling and possibly add my own JNDI capability then don't I effectively have a JEE application server? And then aren't my beans EJBs? Or is there some other defining characteristic? What is it that a JEE compliant app server gives you that you can't easily/readily get from Tomcat with some 3rd party subsystems?

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• how to interpret testng console log message for passing tests?

  - by Kunal Cholera

  I ran testng tests for my test classes, I get the following three types of log output when I run the passing tests. I am using org.testng.AssertJUnit.assertTrue() methods in my tests. [testng] PASSED: testMethod1 on null(test.foo.bar.Class1) [testng] PASSED: testMethod2 on Default test name(test.foo.bar.jar.Class2) [testng] PASSED: testMethod3 Can any one please tell me why for some tests it says "on null" for some it says "on Default test name ... " and for some it does not say anything on the console output. Specifically I want to make it consistent message. Environment : linux Testng framework : 6.3.2beta please advise. thanks.

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• Instantiation vs. Typed reference

  - by Farstucker

  Just when I think Im starting to understand the basics, I find something that brings me right back to reality. In this case, typed reference. I found an example similar to this: class Worker { Boss boss; public void Advise(Boss pBoss) { this.boss = pBoss; } How can you reference methods within the Boss class if its not static and not instantiated? I guess my real question is whats the difference between: Boss boss; and Boss boss = new Boss(); Thank you, FS

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• Returning EF entities using WCF - Read only web service / public API

  - by alex

  I'm currently migrating an application from Linq-to-SQL & ASP.net Web Services (asmx) to Entity Framework and WCF. My question is, I have a bunch of POCO classes which i have xml mapping files for (for the linq to sql) I've replaced my linq to sql with an entity framework data model I've got an interface - something like IService - that has all the methods on it that i need my service to implement - for example: Product[] GetProductsByKeyword(string keyword); In the above case, Product is a POCO. I now have them as entities within my ef data model - i'm using .net 4, and could take advantage of poco support, but don't really see the need - This service is strictly read only. What's the best way of returning entities in my WCF service? I want it to support other client platforms, not just .net (so php guys could use it)

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